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Project Sunroof (google.com)
389 points by Navarr on Aug 17, 2015 | hide | past | web | favorite | 223 comments

I live in San Francisco and just had a solar system installed last week, so I have a few comments about this.

1) It vastly overestimated how big a solar system that could fit on my roof (by about 5x). It didn't care about chimneys or skylights (which are easily visible through Google maps), nor SF fire code which states that you need a 3-foot empty pathway on both sides of the crest of your roof [1]. So for almost every roof with a single ridge, this will cut out a large percentage of the best solar real estate.

2) It didn't include local SF providers in the marketplace which are generally higher rated than national providers and can offer additional SF incentives and cost-savings.

So while the estimation of sunlight potential is really cool, the 3d modeling aspect and size of the marketplace leave a little bit to be desired. This site would probably be good at quickly seeing if your roof has any solar potential at all, but if it does, I'd recommend checking Yelp and having a highly-rated solar company come give you a detailed estimate (which would be free).

1: http://www.sf-fire.org/index.aspx?page=1232

Is the cost primarily proportional to the size, or do inverters present a major fixed cost?

For the former it doesn't really matter how much you can cover, as it's simply an investment with a certain rate of return that has the amount you can invest limited by roof area.

I think all of the hardware will be very proportional to the size. In my case I had micro-inverters on each panel, so it was directly proportional, but this was actually more expensive than having a single large inverter (though more performant).

However, the marginal cost of things like engineering, installation and inspection will certainly go down with the size of the system. How much of that passes to the consumer I don't know, but some of it certainly does. You can imagine the cost of putting 1 solar panel on your roof is not going to be 10x less than putting 10 of them up there.

It is hard to get exact numbers from solar sites as they are very sales-oriented, but it seems like the hardware cost is estimated at anywhere from 20-50% of the total cost of the solar system. The rest of it is engineering, installation, inspection, customer acquisition, profit, etc.

I always find it a bit dishonest sounding when these things are referred to as producing a "savings". Solar on a residential rooftop is not financially sustainable when you consider the cost of capital and require a market ROI. So I assume that lessors in this case are receiving a non-trivial government subsidy. Which means, in the end, that whatever the lessee is "saving" and then some is being paid in additional taxes that wouldn't be there if there were no subsidy. All of which is fine for those that want to pay more for energy that is cleaner. But people should not be given the impression that they're paying less. If they really were we'd all have solar rooftops over night.

This is an argument detached from two realities: (1) that fossil fuels receive enormous subsidies in the US and worldwide, and (2) that there is an enormous impact of CO2 on global climate, health, and ecosystems (not to mention the local environmental and health impacts of coal mining and fracking). When accounting for these costs, it becomes increasingly dishonest to claim that fossil fuels are cheaper than renewables.

That may or may not be the case, but the claims that these systems are "cheaper" prey on economic ignorance.

The reality is the reverse of what you state.

The people who think our current use of coal is "cheaper" are economically ignorant, as it generates many dollars of externalities in pollution that affect health. That cost is born by taxpayers, so by avoiding it, the country saves money and in return passes some on to the person with solar on their roof.

I personally would prefer the more direct and elegant solution of a revenue neutral carbon (& GHG) tax, rather than the current tangle of overlapping regulations, but the immediate result would be the same, people with solar installations would be better off than those who didn't since they'd not need to pay the cost of carbon for electricity they generate themselves.

If you ignore externalities, sure. But that's not how the realities of climate change and pollution work.

Mind your comment and wait and see what will happen after 20 years

20 years doesn't change their price today.

No, only make the world better for our kids, with a small premium to pay today instead of loaning from the future...

Oh so now we're talking about morals. I thought just a minute ago we were talking about dollars.

I wasn't. This was my first comment. And for me morals trump over dollars everytime.

Not to mention that huge ecological damage also has cost someone will have to pay eventually.

So as long as you still believe in your country (which will pay its toll) or your children (which will pay their toll) from that, there's a hidden cost there too.

I'm sorry but you jumped into the middle of a conversation and completely changed the subject so you could argue something that's been explicitly removed from the discussion. The argument was about "is this cheaper than whatever else". The response was "no but it will be in 20 years". That's the discussion. Yes morality and the environment come into play, but that's not what we're talking about.

You walked into a conversation about the impact The Beatles had on music recording technology and said "yeah but John Lennon was horrible to his wife". True, and it's an important point to make. Just not in this conversation.

>I'm sorry but you jumped into the middle of a conversation and completely changed the subject so you could argue something that's been explicitly removed from the discussion.

First, the discussion is precisly what the "people jumping in" contribute. This is not some closed circle of pre-determined friends, it's a public forum. Anybody can jump in. Note how the subthread wasn't even about the original post (Project Sunroof) in the first place, it had been diverted in discussing costs.

Second, I don't see how saying essentially monetary costs are inferior to environmental costs is "changing the subject" much less "completely". It's still about costs in general, and it's still about monetary costs in particular (it's about whether the extra monetary costs are worth the environmental impact, and it's also about the hidden indirect monetary costs from environmental damage).

>You walked into a conversation about the impact The Beatles had on music recording technology and said "yeah but John Lennon was horrible to his wife". True, and it's an important point to make. Just not in this conversation.

In your contrived example, what Lennon did to his wife has no relation to impact of Beatles on the music recording technology.

Whereas environmental costs are still costs (and even have a dollar value, even if implicit). Plus, they are still something to think about when deciding if something is "too expensive" or not.

So nothing like what you suggest at all.

Do you only check the price to determine "expensiveness"? Not build quality, materials, features, and among them, social issues, like environmental impact and working conditions?

From an economic standpoint, none of those things can be described by the word "cheaper".

"the claims that these systems are "cheaper" prey on economic ignorance."

That's the original assertion. Now, if alternative power really was cheaper than coal or oil, we would already have it because businesses would be stupid not to flock to the cheaper option. Instead it's fringe enough that people hold serious debates about whether or not it's a good idea to invest in it. Everyone would drive a Prius if it was cheaper. Everyone would have solar on their roof. But hardly anyone does, because it's not cheaper.

You want to talk about externalities, let's do that: from an economic standpoint, they don't matter. Because the people who are paying for the power plant aren't paying for the pollution. Until the day we hold them accountable and make them pay for the cleanup, traditional power sources will always be cheaper.

So there's your discussion on environmental costs when you're talking economics of power sources. It doesn't even come into play. I drive a gas powered car because a gas powered car is cheaper. If I had an electric car, the power would come from coal, because coal is cheaper. The ship that transports the coal to my local plant is powered by diesel, because diesel is cheaper. And no where along the way is anyone forcing anyone to pay for the cleanup of their mess.

Now you want to talk morals? Yes we all should be embarrassed and we should be fined high and low for what we're doing to our environment. Shame on all of us. You know how often I drive my car when I could have walked? What the hell is wrong with me? I hate myself sometimes. But no one is making me pay for the damage I'm doing. Force me to pay for being lazy! Force the price of gas up, the price of coal! Force solar and wind to be major forces in power generation! But until that day happens, environmental costs are irrelevant when discussing the microeconomics of solar versus traditional power. Traditional power wins every time when you're talking real, direct dollars.

If you don't know if this is the case, how can you say that you know that this systems are not cheaper?

This was true several years ago, but the cost of solar has come down substantially even without considering tax subsidies, and is continuing to decrease at a healthy rate.

For example, Sunroof estimates that a 5.75kWh system would cost $21,500 before subsidies (about $15k after, but we're ignoring that), and that it will save you (gross) $60,000 over 20 years in utility bill costs. You can either:

a) Invest that capital. At a stable 7%, after 20 years, your balance would be about $86.8k.

b) Purchase a solar system for that $21.5k, and invest the difference on your power bill each month. Assuming a base power bill of $200, and the 2.2% annual rate increase that Sunroof uses, you would invest $2400 the first year, $2452.80 the second year, etc. At the same 7% return, then in 20 years your investment balance would be $122.8k, and your power bills would continue to be $0. Remember, these numbers assume an unsubsidized system.

The gain comes from the fact that after the break-even point (at year 12), you are continuing to invest your power bill equivalent, rather than paying it to the power company, whereas in the non-solar case, the increased power bill will never earn you a return.

The downside is that it (with those numbers) takes 12 years for you to come out ahead, and solar tech is moving so fast that the opportunity cost of committing capital to solar today rather than investing it and then liquidating that investment tomorrow to pay for a cheaper and more efficient system may be substantial, but is arguably specifically unknowable. If you don't offset your full cost, the numbers change a bit, as well (but you can certainly compute what happens at a 50% offset for a smaller upfront capital investment easily enough, as well). There are certainly scenarios in which solar is viable unsubsidized today, though.

Feel free to check my math and assumptions: https://docs.google.com/spreadsheets/d/1JoJxX5t7VmRhV1LDI1UF...

I wish "who pays for the system" and "where the system is installed" are decoupled, via a market that lets investors finance the system and the installation and own the resulting energy, and house owners or other sites that merely provide a place to install the panels in return for $x worth of free energy every month. If you're a house owner, you'll bid on the X, or different energy companies could make you offers, and you'd pick one that you like. If you're an investor, you'd presumably choose the site that gives you the greatest ROI — the most sunlight, the highest grid prices, and the least rent to be paid to the house owner (x above).

This addresses your point about upgrading. You can install the newer system on another roof, without incurring cost of removing the older system, and generate power (and therefore income) from both panels at once. As long as the older system is generating more power than its annual maintenance cost, it doesn't make economic sense to dismantle it.

Decoupling also means that if you decide to invest in solar energy, you can have it installed in whichever part of the world (or at least your country) gives the greatest ROI: the most sunlight, and the highest electricity tariffs. Maybe you live in a rented house or an apartment where you can't install solar panels. Giving a higher return will encourage more people to invest in solar.

Other advantages of decoupling will be the ability to invest the amount you want, whether $1000 or $100K, rather than the price of one solar system, the ability to make additional investments if you have more money later on, and the ability to liquidate an investment any time you need the money, or in a financial emergency. People will also be able to dip their toes into this market with a small investment, and see how it performs, before making a larger investment.

What you're describing is what every solar company does right now. SolarCity doesn't sell you panels, they sell you 2 products. The first is electricity from panels they own on your roof. The other is a lease of panels they own on your roof that you get electricity from.

In essence SolarCity and everyone else bids for your roof and business through their pricing. (which currently undercuts utilities).

And SolarCity in return is creating solar bond products essentially, where the market can invest their capital in these roofs that SC is producing energy on, with the monthly bills as interest.

But it doesn't solve the issue the person you replied to highlighted, which is that it may or may not be financially advisable to 'hold out', and buy solar when the price has come down. After all, even if you don't buy and own the panels, the lease is still a 20 year contract. And there's no way SolarCity or any company would reduce those to short-term contracts because there are fixed costs that can't be recuperated in the short-term, meaning you need long-term contracts to get an ROI. (sending technicians to replace installations every few years wouldn't make financial sense).

So the end result right now is that yes, you could in a way (by investing in solar companies or their financial products) invest in other people's roofs, despite not dismantling panels on your roof, in say 5 years from now when new installations are financially better performing than your roof panels. But it doesn't magically make your investment in your own roof (or anyone's roof, 5 years ago, for that matter) disappear. The money is still locked up in that roof (whether you paid for it, or locked up money by signing a 20 year contract), and so merely decoupling everything doesn't solve that issue, and in many ways we're already decoupling to a large extent with the securitisation of roof installations.

I see. Thanks for educating me on how SolarCity, and solar companies in general, work. Your post makes a lost of sense, and it seems that we agree on many things.

As for money locked up in solar panels, that's no different from traditional investments. If a factory is built, a better factory may be built a few years down the line, rendering the first one an inefficient use of capital. That's an unsolvable problem (unless you have a crystal ball), and it doesn't deter people from making investments. What makes solar different?

What we really need to do this is the breakdown in cost between the hardware and the labor required to install and certify the panels. The hardware is likely to continue to fall rapidly, but the labor costs is likely to fall much more slowly (or at all). At some point even if the panels are free the labor required to install them means that the prices will reach a plateau.

The common definition of "savings" is a reduction of cash outlay for the purchaser. The fact that there are government subsidies (or surcharges) involved is not relevant for that calculation.

The Google site is extremely thorough -- for the case where the consumer is buying the panels, they calculate the time to break even, but also a net present value given a 4% cost of capital. Same thing for the lease cases -- for an example I ran, the lease would cost $96 per month (fixed for the 20-year life of the lease), and offset $115 of a monthly $120 electrical bill at today's rates. So, it would generate cash savings for me from day one. Most solar leases in fact GUARANTEE that you will pay less for electricity after the install. So, "savings" should not be in quotes, it's a real savings for the lessee.

As for your argument that we might all be better off if we didn't have to pay higher taxes for the subsidy -- maybe, but my decision to install solar or not is going to have a negligible impact on my personal tax rate, so I should value any savings against a fixed tax rate that doesn't change as a function of my decision.

You are correct - the impact on your personal tax is negligible. Solar accounts for something well under 2% of total energy generation and residential rooftop far less. So almost all of your subsidy is paid by others. That doesn't make the over all analysis any more sound. What if we all had solar on our rooftop? Energy would cost more. The savings would be negative.

I don't accept your conclusion. If we all had solar on our roofs, there are many possible factors that could reduce power rates (including tax burden, by your definition):

-- fossil fuel prices would drop, since demand would fall -- we would spend less tax money on grants and subsidies for oil and gas marine terminals -- fewer emergency responses, disaster clean ups, etc. for fuel transportation mishaps -- maybe we could avoid or sit out the next land war in the Middle East ...

Additionally, even without a tax subsidy, installing solar on my roof in CA would generate a positive NPV over 20 years. Here in CA, it's just plain cheaper than the utilities, even without the (nice to have) tax subsidies.

I don't understand how people connect oil and gas imports to electricity generation. Go read this article http://www.washingtonpost.com/graphics/national/power-plants...

Now how much electricity is generated from oil in the US? A whopping 1%.

Now while it is true that we import a lot of natural gas... "Natural gas imports to the United States, 98% of which arrive via pipeline from Canada, have decreased almost every year since 2007, and in 2014 reached the lowest level (2,636 Bcf) since January 1995." According to http://www.eia.gov/naturalgas/importsexports/annual/.

So if you think putting solar on your roof, or wind, is going to make any OPEC countries upset please think again.

Absolutely true, but nuance is necessary.

For one, a major part of energy use today is non-electric because it makes more sense to use fossil directly, than to use fossil to generate electricity and use that. But once you have cheaper electricity than fossil, and cleaner, you can start to see these industries shift towards electric.

Not everything is susceptible to that, like say chewing gum made of oil partially will not go electric obviously. But transportation likely will, and heating could possible go renewable (not necessarily electric. e.g. geothermal, solar thermal etc).

And so the cleaner electricity is, the fewer barrels of oil one would need in some non/low electricity industries right now, transportation being the biggest.

Secondly, it's true that the majority of US oil isn't from the middle east, but that doesn't mean it doesn't matter to the US, that's a silly argument to make. What happens if the middle east produced 0 oil the next 100 years? You can't say 'who cares', obviously the world would go into a state of shock. Oil prices would skyrocket, production and consumption and worldwide trade would all drop sharply and recessions would break out. Which leads to unemployment, social welfare issues, friction, don't even get started on wars between countries, civil wars would be damaging enough.

The 1970s showed how brutal oil politics could be to the economy, and that was small-scale compared to the most far reaching scenario.

And beyond that, anyone who exports to the US, like Canada, would think twice, after all why not sell it to China who's willing to pay $500 a barrel, too?

Also, even if you don't import the energy yourself, that doesn't mean the US can't profit or doesn't profit when US companies are involved in the oil industry in the middle east, even if the region doesn't export the majority of its oil to the US.

And lastly, even if you don't import it yourself, you may want to control who has access to the oil, and in what currency it's sold. You wouldn't mind Germany selling Nuclear reactors to the Netherlands or vice versa, it's a different story for Iran. Just like you might want to have some control over oil reserves because your control means China doesn't have it, despite not being a top customer yourself.

As for the final point, the concept of petrodollars is real, and the fact oil trades are denominated in dollars, and the effect the standing as a reserve currency has on the US is significant.

The US doesn't have to be a customer of middle east oil to have a benefit in controlling it, that's naive and it's getting a bit tiring to see everyone act like you're a dumbass when you make this claim, always immediately pointing to charts of Saudi Arabian and Iraqi oil imports being so small compared to 'omg lol US production & Canadian imports, you're so dumb, bet you didn't know that'. Don't get me wrong not saying you do this but it's a common theme when discussing the issue.

And really just look at history. You don't have to be a conspiracy theorist to look at the middle east and conclude oil plays a role. When Iraq was getting decimated on forged evidence of WMD, guess who was developing WMD, admitted having WMD, and tested WMD, not just any kind but the nuclear kind? North Korea. Otherwise a beacon of democracy and human rights and quality of life. Comparing the eagerness and focus on invading this country and Iraq is telling.

I mean do you really think trillions of dollars were spent on an intelligence fluke? Or that the carter doctrine was some minor policy plan that has nothing to do with oil?

Besides it's not like this is a secret. People like Cheney openly talked about the importance of controlling oil reserves, how demand would outstrip supply in the coming decades, and talking about how 2/3rd of oil is in the middle east and that access is important. Which brings up the final obvious point, which is that the US isn't running energy policy because of today's needs, but the needs in 50 years from now, so pointing to today's import charts is not comprehensive enough an argument.

So hell yes, renewables have a substantial impact on all of that. They're not the entire story, but a substantial part of it.

"Additionally, even without a tax subsidy, installing solar on my roof in CA would generate a positive NPV over 20 years." I would like to see this analysis. I know that there are certain (mostly remote and very sunny) areas of the U.S. that have demonstrated unsubsidized market viability. But even then only with utility scale installations. I would think rooftop surpassing grid parity with conventional energy would be a pretty big milestone. Not doubting you, but I'd love to see it on paper.

Go pick an address in Silicon Valley (take for example 2 College Ave, Los Gatos). Set the monthly electric bill to $125. The calculator recommends a 4.25 kW installation, which has a 20 year NPV of $12,056, if you click into the detailed analysis and check the last line.

Subtract out the $5028 Federal tax benefit, and you are still left with a $7000 20-year NPV (assuming 4% cost of capital).

Still a positive ROI over and above inflation, even without a rebate.

I guess it depends on what you count as government support.

For example if you pay $50k for your installation, you could depreciate it within 5 years or so by 85%, which reduces your tax payments in total, at a 35% tax rate, by $15k.

That's $15k saved, whether you call that government support depends on whether you think that's 'normal business depreciation' or 'solar specific fiscal policy' I guess.

Same with RECs, they're government support in the sense the government sets requirements on companies to buy them, thus creating a market for solar producers to sell them. This isn't energy being sold, it's more like a carbon tax thingy. You could see that purely as a tax on non-renewables (which imo it is), or as government support to renewables (which it's technically structured as).

So the federal tax benefit, while large, is far from the only incentive.

OK, but as an individual homeowner, I can not take depreciation, nor can I sell REC's. I'm just buying solar panels and putting them on my roof ...

... And again, to compare apples to apples, you'd have to tease apart the tax benefits given to existing energy companies over the years to get a real accounting.

You're replying to a guy who talked about 'even utility solar'. So I'm just giving the story for utility solar.

And it's import to note that the biggest solar companies right now aren't residential, but utility, so we're not talking about some niche aspect of the industry here.

And even the biggest residential solar companies their main products are leases right now, meaning they do get to depreciate their installation costs and then either let you rent the panels or buy electricity from them.

So in the vast, vast majority of installed solar panels, depreciation plays a gigantic role.

As for SRECs, you could sell them actually, don't need to be a business to do so.

Actually by the standards of rates of change in the energy industry, we are going to all have solar panels powering our homes 'overnight' (see the rapid growth of solar forecast in slide 33 of the doc linked below). In many areas, due to rapid price declines and relatively low prevailing interest rates, solar is cost competitive without subsidy now so the ROI is real. As cumulative solar installations continue to grow, we will continue down the cost curve shown on slide 13 and that will be true for more and more people. Which means that subsidies today can actually lead to long term lower energy costs as prices continue to drop. On that topic, we should all be thanking Germany for being farsighted enough to invest in subsidies to keep the industry going for long enough to get us down to where we are on the cost curve today.

Bloomberg new energy finance talk slide deck: http://about.bnef.com/content/uploads/sites/4/2015/04/BNEF_2...

Well, look at the subsidies for the existing energy companies. Nuclear companies get the waste handling for free, if they break regulations, often the government pays the bill...

Coal companies never pay for the damages to the environment their huge quarries do...

Subsidies for solar are just one part of it.

If you take these subsidies that you give the energy companies, and add them as tax to the electricity price, you end up with electricity costs like in Germany – 0.40$ per kWh

If what you're saying is correct, if subsidies were removed across the board taxes would go down, energy costs would go up and solar would take off and replace coal because it would be the (real) best deal.

What do you think why German electricity companies are trying to sell their gas and coal business and focus on renewables as much as possible?

In Germany, the effect is even stronger: As we are taxed per kWh, the electricity is quite expensive. On the other hand, this money is then spent on subsidies for solar and wind. Overall making solar and wind so extremely cost effective that anything else becomes stupid.

And, at the same time, it leads to people saving really a lot of energy. A family of 4 using 3000kWh per year or less is common.

Even fairly conservative estimates of the negative externalities of coal do in fact indicate this for daytime loads.

Actually in many places solar is currently cheaper than the utility, without having to be a cheaper generation source.

For example a cost of 15c per kwh cost from solar is pretty trivial in many parts of the world nowadays. But here's the thing, for example in the Netherlands, I pay 7c per kwh for electricity, and then about 13c in energy specific tariffs, and then VAT on the whole lot. My final electricity price is about 3x (22c) the cost of the electricity itself. But for every kwh I generate myself and don't buy, I save 22c.

In other words, at a hypothetical cost of 15c per kwh, twice as much as electricity from my utility, I save almost half of my bill.

That situation differs radically between countries and even states, but again, savings on solar are a very typical story nowadays. I'd say most solar buyers today are saving money. 5-6 years ago that was different, when most people who bought were still buying with a moral position in mind and paid a slight premium.

Mostly, I don't think people realise how incredibly subsidised solar is. Per unit of energy generated, direct taxes/subsidies are much, much higher than oil. The other part of that story is that we have path dependency in oil and that the carter doctrine has cost trillions of dollars, and that externalities aren't priced in much for fossil. (e.g. cost of pollution, droughts etc).

For example, here's an interesting thought. For every $1m you buy in solar, you get about half a MW in capacity, which generates a little under 1 GWH per year (rounding it up very heavily here but you'll see it's mostly irrelevant). Now here's what that means. First of all, you can get a 30% tax credit, which you can sell. That's $300k recuperated. Then on a portion of the cost, 85% iirc, you can depreciate within 5 years or so. At a tax rate of 35%, that's a total of $300k in tax avoidance due to depreciation. So right off the bat in tax structuring, you've already gotten more than 50% off. Then, your almost 1 GWH per year generates solar credits, which you can sell, too, for about $100k per year. And yes you can presell these for 10 years into the future.

And then and only then, after you've paid $1m, received $600k in tax back from the government and sold solar credits for just the first 10 years for $1m (on a system with 20-40 years of lifetime at least), when you already made $600k accounting profit without generating a single electron, then you can start to actually sell the energy to an offtaker (like an Amazon warehouse) for about 10c per kwh, making you a little under $100k a year.

So you invest $1m, you get $1m, you get $600k in tax benefits and annual income of a little under $100k. Sounds insane? Well it sort of is. It depends on the state, some states are crap (low cost of electricity, low price of solar credit market, little offtaker demand, few solar resources (sun), difficult regulations etc etc), some are great.

And beyond that, solar is simply becoming cheaper really fast. For example, SolarFirst just signed a contract for a 100 MW solar project at a kwh price of 3.8c. Pretty insane.

Anyway in short the notion that solar savings are disingenuous is completely false. In fact virtually all of the big solar companies offer leases right now, where you pay nothing upfront, you don't own the panels, but you lease them on your roof and pay an electricity bill that's lower in the vast majority of cases than your utility. That's their main selling point.

Their vendors also don't include the roofing type. For example, I have a flat tar roof and many vendors, such as Sungevity, won't install on it. Local vendors will, but are not on the list, and require I install a new roof first. There goes the $24k in savings for buying outright!

Would that be a sunk cost, or would a new roof increase the value of your home?

Which installer did you choose, and would you recommend them?

I used Luminalt [1] and they did a great job throughout the whole process. The installation job was at the highest degree of quality and professionalism that I've experienced.

Though it hasn't been inspected or turned on yet (happens later this week), so I'll see how close their projections were to reality over the coming months as the juice is generated. I did my own projections independently and found that their projections seemed to be on the conservative side, so I'm optimistic.

1: http://www.yelp.com/biz/luminalt-solar-energy-solutions-san-...

Did you choose to lease, loan or buy? Would be interested in knowing the factors driving your decision.


granted it is in dutch and made by a completely boring governmental institution. OTH it's made with openstreetmap.

It's not a governmental institution but an NGO which unites many local governments and other participants.

They use high resolution 3d surface information (elevation data) and weather reports to assess the efficiency of solar panels. The map for my house accurately shows how much efficiency can be expected on each part of the house. This takes into account neighboring buildings and trees. The site also calculates a number of scenarios and allows you to easily request offers and show how long it takes to earn back your investment. They cleverly compare this to interest rate. E.g. on my house, investing in solar now would yield 4.5% interest over 20 years (given certain assumptions).

It is a very impressive site.

And http://www.zonnekaart.nl, which links to similar initiatives, such as zonnekaart.nl (gives detailed information about what parts of roofs are useful) and http://www.zonnig.haaglanden.nl (cool color scheme)

Want to see what it does, try City Hall:



"1,960 hours of usable sunlight per year"

I wonder how they arrive at that number, and how accurate it is? Anyone in SF want to try a few addresses in Outer Sunset vs the Mission?

I'd be interested in seeing that number alone mapped out over the US on a zoomable map.

FWIW, at least in my case, the numbers here seem optimistic. I had SolarCity come out and do a proposal for my house in San Jose about four years ago. Because my single story house is surrounded by big trees and two story houses, they said I only had a small area where they could install panels with sufficient efficiency, for a 3kW system. Sunspot says I could install an 8kW system covering 1475 sq ft, compared to about 800 sq ft for the Solar City system.

Perhaps it should link to a solar installer, and a lumber jack :-) More seriously though, I installed solar about 13 years ago now on my roof, California has some case law about trees blocking solar, post install, which was decided in the favor of the solar panel owner. The city tree across the street had gotten large enough in the last 10 years to start shadowing some of my panels. So when the arborists were in our neighborhood I pointed it out, and they cut a chunk off the top of the city tree so that it would stop doing that.

At one level this was "fine" in the sense they were totally ok with that and felt they were obligated under California law to do so. At another level, "solar rights" ala "water rights" or "mineral rights" for a property are probably going to become a thing at some point.

In your case, if the trees around you fell down for some reason, you install solar, and the landowners/city replant trees, by virtue of the fact that your solar is there it will impose a trimming burden on the new trees. But there is no requirement that people clear trees to make it possible for you to exercise your "solar rights". That is the next kerfluffle I expect in California.

> Perhaps it should link to a solar installer, and a lumber jack :-)

Let's not be cutting down the carbon dioxide remover when we're trying to go eco-friendly. :)

Any gains from PV would be washed away by increased air conditioner usage. If you have a house in shade, be very happy.

Energy wise, I wish my lot were less shady. I spend 0kWh per year on AC (days over 90 are rare), but heating is another matter.

Which reminds me. If anyone knows a good way to retrofit an house with no ducting and no natural gas for any form of efficient heating, let me know.

If you have a crawl space or basement, you can install electrical under-floor heating at fairly affordable costs. Basically the heating element comes in a roll which you then tack the the underside of your floor.

I have lived with such a system before for a year and it was both easy to use and did a good job of heating the space. I don't remember the electricity costs so I can't comment on the economic efficiency, but AFAIK it's moderately good. I wish I had it in this house instead of the noisy, draughty, and inefficient gas-powered duct heating which I avoid switching on whenever possible.

Heat pump! You can get wall mounted units that work just like an A/C (but in reverse of course.) Efficiencies have gotten pretty good in the last decade. Check out units made by Daiken, Hitachi, Mitsubishi for example. I know they make multi-room versions. You'll need to run the refrigerant lines, but that's usually a much smaller task than adding ducting.

This is the direction I'm most likely to go. The other option is a fireplace insert. Cheap, but not as environmentally friendly.

Any electric heater will be approximately 100% efficient, but electricity is generally much more expensive per unit energy than than natural gas or oil. If you have decided that electricity is your best option, you should compare convenience, installation cost, and whether you want to heat specific areas or the entire house.

However, there's a big difference between electric resistive heating (generating heat) versus electric heat pumps (moving heat around.) The latter can be 3x or more efficient than the former.

No access to natural gas? I'm assuming you live too far from the gas lines to make a new gas installation possible?

That said, I had a instructor who's friend bought a house out at the beach 30 years ago. He didn't know what to do about heating.

He decided to put a large diesel tank on his property, and use that fuel to run a boiler. He installed baseboard hydronic tubing. He was very happy with the heating set up. His previous system was electric, and his monthly bill was outragious.(electrical rates really do vary from area to area.)

He also had an old Mercedes diesel automobile. One day he used the heating grade diesel for fuel for his Mercedees. His car ran fine. He was paying someting like 35 cents a gallon for gas. He used that car to commute for years. There are no taxes on the heating fuel, or at that time.

(That 35 cent quote is from a story told to me 20 years ago. I don't know if heating diesel was ever that cheap? I was told this story from a instructor who I don't completely trust. He tended to embellish.)

That said I always thought if I lived in an area where I couldn't use solar, or natural gas; I would definetly use a boiler, with propane, or diesel fuel? They make condensing boilers that are very efficient. I installed one and it wasen't that hard. I don't know if a condensing boiler can use diesel fuel, but I know you can use them with propane.

If you decide to do the work yourself; buy the third edition of Modern Hydronics. It's expensive, but go for it. Hole yourself up in a room for a weekend, and read that book. It's geared for large hydronic installations, but will handle residential installations fine. Hydronic heating is really under utilized, especially on the west coast. It's a great, energy efficient way to heat a home. I bought a fancy condensing boiler and happy with it, but I have a feeling I could heat a house with a water heater if your have enough baseboard, or tubing? And you live in a temperate climate?

Of course, hire a professional if funds are tight. Make sure the professional knows about boilers, and hydronic heating. A good first question for the contractor is what brand of 02 sensor he/she uses to calibrate the boiler. If he doesn't immediately come up with a answer, or looks confused--run. The second question should be "could you write down the what a primary/secondary hydronic piping configuration would look like?" Verify he knows what a primary/secondary system looks like, and why it's important.

Hydronic heating is vastly underutilized in the U.S., at least in California? I don't know why it isn't used in more situations? I guess engineers feel that if you are going to need air conditioning, why bother with it? I have heard incorporating air conditioning with hydronic heating is not that difficult? As to keeping zones at different temperatures, I did not find that to be a problem if you run your zones correctly.

(One other painful lesson I learned by relying on wood burning too long. Don't buy a cord of wood off Craigslist. I guarantee a guy will show up with less than a cord. If you are forced to use the fireplace; put a insert in.)

Diesel in the US has a red dye added if it's for agricultural use. "Detection of red-dyed fuel in the fuel system of an on-road vehicle will incur substantial penalties."

Presumably you have to piss off a cop in your diesel-powered vehicle enough for them to test your tank.


Hydronic heating is great, but I don't think it's well suited for retrofits.

I'm not very far from the gas lines, just on the wrong side of the street, and digging up the street is expensive.

Oil burning is more expensive than using a modern-day electric water heater, by the way. Oil has gone up in price and electric heaters have gotten much more efficient.

That assumes you have an air conditioner. In coastal California, they aren't common in older homes.

Actually in California a solar panel owner already does have solar rights.


"25982. After the installation of a solar collector, a person owning or in control of another property shall not allow a tree or shrub to be placed or, if placed, to grow on that property so as to cast a shadow greater than 10 percent of the collector absorption area upon that solar collector surface at any one time between the hours of 10 a.m. and 2 p.m., local standard time."

There are a number of exceptions later in the act, including a notification requirement.

However, once a solar system is installed - a neighbor can't cause the system to be shaded with impunity.

Maybe panel prices have dropped enough in the last 4 years that partially-lit areas are now worth covering in solar (cost < savings * acceptable ROI months).

So City Hall would actually save less money (12k vs 13k/14k) than the two regular homes I tried in San Francisco. If the numbers are correct, we're looking at $650-700 a year in savings. Not bad, but not that great either, especially considering heating alone in both buildings I looked at ran $150-300 / month (including summer which is hardly warmer at night in SF). Can solar panels be installed at such a price on a regular home? I doubt there's any incentive for City Hall here.

EDIT: I also doubt the calculations are correct considering that city hall's roof is many times larger than the two homes I looked at, yet saves less money.

One of the tunable parameters is the "size of your electric bill", which defaults to $150/month and maxes at $500/month -- far too low for a city hall, I should think. This is the limiting factor here, not the size of the roof. At $500/month, the recommended installation size is 765 square feet, but the total roof size is 50,171 sq feet. Only a small fraction of the roof area is being used.

This has clearly been designed for residences and not larger buildings.

I'm guessing you left the average monthly electric bill slider at the $125/month position. You'd have to adjust the to what it actually is for City Hall, which I'd think is a lot more than $125/month.

There's no such slider on my page, only a text box. Tried disabling privacy plugins, but they're not the culprit.

It looks like it's only tuned for residences (and maybe small apartment buildings) as you can only set the max electricity bill at $500 per month. I'm sure the city hall's bill is much higher.

Entered my info. Got a call within five minutes and was then asked the exact same info. Company said I don't use enough electricity to make it worth it. Wonder how much they had to pay Google for that lead

A better link, although I find it interesting that this is primarily an advertising play. Take information they have (Google maps) and turn it into a "qualified lead" system for Solar installers. Has to pay pretty decently on a conversion.

That said, it would be super helpful if they marked addresses as "already have solar" so I would stop getting robo-calls from solar companies trying to sell me solar panels.

Can anyone with more knowledge of solar technology speak to this?

I know nothing about solar technology developments. I am interested in adding solar to my house some day, but concerned about spending a lot of money today for solar panels that will either (a) be much cheaper in 5-10 years, or (b) be replaced by much more effective panels in 5-10 years.

Assuming that the economics of it are the only motivation for going solar, and that with current technology and pricing the panels pay for themselves only after ~10 years, am I better off waiting a few years to get more efficient/cheaper panels, or is it unlikely we'll make significant advancements in these areas, and/or do current government incentives (which may be ephemeral) make up for the advantages of future tech?

I'd go for it. Prices will get cheaper (virtually guaranteed), but incentives will also go away (guaranteed, deadlines are already set).

If you only care about the financial decision, then to be honest... not much beats investing in e.g. a broad S&P 500 tracking index. 7% inflation adjusted annual returns + dividends which you can reinvest to go up to 8-9%. Over a 20 year period that's 5x. I'd tune that down to 4x given there's risks and historical returns have been better than they probably will in the future. But it still means at 4x that your $15k solar installation could also have made $60k in the same period.

And there's no way a $15k installation will generate $60k worth of energy, somewhere between $10k and $20k depending on the cost per watt, solar capacity factor and local energy prices. (California does quite nicely and is on the upper end of this spectrum). About a third you get back from the gov, so in a 20 year period in Cali, investing $15k (subsidies included) you may get $30k-$35k in savings if you go solar.

It's really nice but it doesn't beat the market, and most states have cheaper rates than California which is like 30% above average and much fewer sun hours, and less competition, too. Wouldn't be surprised if installation costs were relatively more competitive in California.

So my point being is: 1) it's a great investment and I'd personally go for it. 2) it's, purely financially, not the absolute best way to spend your money, even if it saves you money. So there's still an element of 'I think solar is important' at play. 3) solar tech will get cheaper, but subsidies will fade out.

My take: Further increases in efficiency could mean that you could install more capacity on your roof, or the same capacity in fewer panels. Assuming that you can fit enough panels to cover 95% of your demand on your roof, installing more panels doesn't make sense (over-generation is not really profitable today). At the same time, a lot of the installation costs are independent of number of panels (permitting, estimates, wiring to the junction box), so installing fewer panels won't bring the cost down tremendously.

At the same time, tax subsidies are scheduled to start phasing out, and utilities are making noises about discontinuing some of the more favorable rate plans that allow 100% net metering (generated power is credited at the full retail rate, not at the wholesale rate). Either of those changes would negatively impact ROI.

It's hard to know what will happen in the future, but with the current environment, many people can lock in a favorable 20-year ROI for a system today.

And advancements in fusion, fission, wind, etc that could make today's solar less worthwhile.

No one can predict how much the landscape can change in that time and I wonder if Googles 20-year savings model tries to account for predicted advancements -- and also importantly if their "savings" accounts for the time value of money -- the amount that could be had just by investing generally instead of investing in your own solar. Time to investigate....

Edit: Google "Assumes 2.2% annual increase in electricity prices." That's interesting. We should be talking present value terms so inflation is irrelevant. Are they assuming no tech advancements in the next 20 years? What would be driving up those costs other than inflation?

My personal take is to minimize the amount of temperature variance over time so I'd invest time and money in insulation, weather stripping, other upgrades first as well as reducing my electrical usage in general.

Right now, I'm at a point where I need to use a FLIR to investigate more improvements after which will I then think about solar but it's nice to read up on solar improvements.

That's what subsidies are for - to incent you now, and when panels are cheaper and more efficient later, the subsidies go away.

If you do go for solar just make sure you install it before December 31, 2016 as that's when the 30% Federal tax credit expires (note: this is if you buy, not lease the panels. Leasing does not earn you the 30% credit).

The 30% federal tax credit does apply to leased systems. It's just that the leasing company gets the credit "on your behalf" (also known as keeping it for themselves) but includes it in the calculation of how much to charge you as the lease payment.

Off topic but the Google Sunroof logo is very similar to MyHealth program logo in my province (https://myhealth.alberta.ca/).

For those who got 404 from their IPs: http://www.youtube.com/watch?v=_BXf_h8tEes

Are firefighters any less likely to enter a house fire where the roof is covered in heavy solar panels? I've heard stories, but never dug into whether it was anti-solar FUD.

No. The weight of the panels and the strength of the roof are accounted for when the system is designed.

Modern lightweight truss construction fails so quickly under a fire load, we're unlikely to make an aggressive attack if the fire has been burning in the attic space for any length of time, panels or no.

It smells of the anti-hybrid astroturfing from a decade or so ago where numerous Ford and GM employees would be glad to tell you on social media that if you get into a car accident in a hybrid, emergency services will leave you to bleed out and die because its a hybrid so you should have bought a SUV or truck like a RealAmerican(tm).

My father in law did the volunteer fire dept thing in his rural area and its very depressing how quickly a typical house becomes unsaveable in a fire. So it is true that most houses with solar panels, in a fire, will end up a total loss, but that's true of most houses ... period, nothing to do with solar panels.

My advice from the frozen north is solar panels are extremely light weight compared to slush/snow covered shingle roofs, which don't seem to slow down firemen very much. The total mass of a couple inches of rain soaked slush snow is unbelievable, many thousands of distributed pounds on a typical roof.

Everything above is correct. (I'm a volunteer firefighter.) Firefighters nowadays are trained to deal with the high-voltage DC that's present in hybrid and electric cars. It may take a little longer to extricate a victim, but it won't stop us. As for houses, we won't bother entering a burning residence at all unless we're likely to find a person still alive, or the nature of the fire is such that the danger to us -- with our PPE and training -- is minimal.

I assume part of the training is how to locate the right stuff to cut to shut off the high-voltage connection? Have you ever had to do that in practice, and if so how hard is it on a car that's been mangled?

The car manufacturers use bright colors (typically fluorescent orange) on cables that carry high voltage. We don't cut them! Too dangerous. Instead we avoid them, and assume that the car is energized.


I know you wouldn't cut high-voltage wiring, but I know at least on a Tesla there's a low-voltage loop exposed for firefighters to cut, which then isolates the high-voltage system as well as disabling the air bags and such. That's shown on page 10-13 here:


I have no idea if this is a common thing or not. Anyway, thanks for the PDF, very interesting stuff. Assuming the car is energized seems sensible. Even with a loop like Tesla has, I imagine you can't count on that having the intended effect after the car has crashed.

Tesla actually does a really nice job of providing training materials to first responders:


You can watch a Tesla get cut up in this video:


Very nice. I was somewhat aware of the materials they provide, but I didn't know that video existed. I'm kind of impressed they sacrificed a car for it (although I suppose many of the valuable spare parts remained untouched).

Thanks for the reply, and the job you do.

Seems like it's likely mostly anti-solar propaganda, but I guess there is some concern regarding the electrified nature of solar panels rather than their weight.


I care little about the house in a fire. I do care about its occupants, and also the safety of the firefighters attempting to extract anyone still inside.

I've not encountered discussions of solar panels in firefighter training, but my intuition suggests it's probably not a big deal. For nighttime fires, the panels won't be generating any electricity anyway. For daytime fires, smoke and water will likely occlude the panels and decrease their voltage. Firefighters ventilating the roof would need to be trained to avoid HVDC wires connecting a series-connected panel array to the inverter. We might also just lob foam onto the panels and turn them off that way.

Three layers of asphalt shingles (which many houses have) is a lot heavier than solar panels. Firefighters assume residential roofs to be generally pretty crappy in a fire. Their decision to enter will be based more on the extent of the fire and whether they believe anybody's in the house who can be saved.

Forgive my ignorance, what does one do during non-insolated hours? Do solar cells typically come with battery packs or does one just pull from the grid?

If the latter then the cost savings are a bit less impressive than stated.

Also can you put power back into the grid in San Francisco? Is that benefit included in the cost savings estimate?

Solar power systems don't necessarily come with batteries but a decent installation company should be able to propose and implement an integrated system. The Tesla battery pack is an example of some recent innovation in that area.

You can sell power into the grid but PG&E only has to pay you wholesale rates, 3-4 cents per kwh, not what they are charging you to take the same amount of energy out, which is 34 cents per kwh at the top tier. It's basically a scam. You don't want to overbuild on the assumption that selling the surplus would be profitable.

> It's basically a scam.

Why is it a scam that PG&E won't pay you more for power than they can buy it wholesale?

The 3-4c wholesale rate is for base power (giant infrastructure generators, hydroelectric dams and such things), but solar knocks the top off the mid-day demand curve, at which time PG&E is paying much more for "peaker" power generation. But they don't have to pay you the peaker rate, they pay you the baseline rate.

Anyway, to my mind, any system in which current comes out of your PV installation at 3 cents and flows directly into your neighbor's air conditioner at 34 cents is a prima facie scam.

Even peaker plants run ~15 cents these days, since the price of gas has fallen so low.

edit: I'm more familiar with the Texas grid, but beyond the cheapish price of modern peaker plants, in that case the most expensive input sources (small peaker plants, and esp. spot-market purchases) are rarely used at all. Demand prediction and management is good enough to avoid the more expensive inputs, through a mixture of local generation management and advance wholesale purchases on the DC interconnects. On the handful of days when some issue causes a shortfall, it would be valuable to buy residential solar inputs, but this happens about 5-6 days a year. To handle those days, most utilities have a savings-rebate program, where if you agree to reduce your usage between 2-5pm on these handful of days, you get a $0.60/kwh credit. So they solve their occasional peak problem by just turning your thermostat up 2º and "buying" the unused energy at a premium price.

Yeah, but that makes PG&E's "smartrate" summer afternoon price of 75c per kWh even less justifiable.

This data may not be publicly available, but I'd love to see graphs of current flowing out of PG&E substations vs. time of day. At some point the PV generation capacity is going to make them have weird upside-down diurnal cycles.

Something I worry about with solar is once power is psychologically "free" I'll be tempted to set the thermostat down to 65F or whatever, and end up paying full rate when clouds blow by. I think it would be difficult not to increase power use once its free. I'm not talking about explicitly leaving stuff on for fun, but more like "well, power is free, so I guess I can afford a tropical reef tank instead of a plain fish tank" and there goes 1 KW of lighting continuously plus a chiller whereas right now my fish and I are very happy with ten watts of LEDs. This kind of thing needs to be taken into the financial analysis.

Also in the winter if I have "free" electricity and have to pay for natgas to heat, I'll simply buy a raid array of plug in electrical heaters to eliminate that "free" electricity and eliminate paying for some natgas. Or maybe I'll just install a bigger raid array. Either way, I like free heat in the winter and typical analysis usually doesn't consider heating. If you pay me 3 cents per KWh in the winter, and charge me 15 cents equivalent in natgas energy, I'm not going to sell you a single KWh until my house is above 75F in January.

Your array of inexpensive resistors will heat your house just as much (or probably much less) than a window would.

But you can use heat pumps, and you can do deep storage of summer heat, for use at winter (no idea about how well it works at your place). Both are very efficient.

Anyway, if your marginal price for electricity is zero, and the marginal externalities are also zero, there's not much problem in using it.

Heating your house with electricity is extremely inefficient. 5KW of "excess" electricity won't go very far in heating your house when it's cold outside, and any excess you might have will be less in the winter because of your latitude.

I'm not saying you can't do it, but even with today's cheap solar panels it's not likely to be a good value proposition.

Heating your house _directly_ with electricity is inefficient. Using that electricity to run a heat pump can be very efficient (assuming you have a large enough heat reservoir (e.g. a few hundred feet of pipe buried underground))

How can heating your house with electricity be less than 100% efficient?

Turning electricity into heat isn't all the work you can get out of the energy. Heat pumps get even more, by using the energy to move heat from one place to another (e.g from ambient outside air to the volume to be heated), and the heat from this process also heats the volume.

If the air outside my house is warmer than the air inside my house, I'll just open the windows. Generally when one needs a heater it is because the system surrounding the house is colder, sometimes much colder, than the house itself.

Cold makes it harder on the heat pump, but not impossible. Heat pumps use a compressor (just like AC unit). If the pump can create a mass of gas colder than the outside air, then that mass will be warmed by the outside air (no matter what the absolute temps are).

In the limit of course (too cold outside), a heat pump is just as efficient as using the electricity for heat directly.

If that electrical energy was generated from gas, then it's often more efficient to burn the gas directly for heat. So depends when you take as the starting point for 100%

I suppose that part of the price difference is that you're an unreliable source of unreliable electricity, whereas your neighbor pays for stable, reliable service.

Is there no real solar power market then? If your local utility is a monopoly then you basically have to accept whatever the utility wants to pay you (even far below 'market' rate). You have no power to negotiate, only capitulate or try to get the local regulator to enforce fair trade.

I suspect you'd fare pretty badly in a market, even if a better one existed. In Texas's deregulated electric marketplace, the market price for large-scale solar installations selling into the grid has fallen to around $0.05/kWh. Power from a single small-scale residential installation with less reliable delivery is probably worth less than that.

Depends on how much "better" the market is e.g. if it priced in the greenhouse gas externalities, the avoidance of transmission losses and grid upgrades etc then solar may be worth triple the residential rate. I believe a couple of states have calculated "value of solar" to use as part of their grid regulation, though specific factors like mix of gas and coal production and projected grid expansion factor into this.

Any reasonable grid would also be wired such that the power you generate will first go to your neighbors, if they need it, instead of 'round-tripping' to the utility and back. So, the utility is taking a huge cut even though it isn't really a factor in the transaction.

There are of course large-scale infrastructure costs (you get to fail-over to nuclear/coal/gas/wind/other), but it seems like all of those things should be accounted separately instead of all being lumped into two line items on a monthly bill from your local monopoly.

Local conditions may vary, of course, but if just go with the completely unimaginative system, and you live in California in PG&E territory, there is no effective market.

Well, you can go buy a battery.

I'm fairly certain San Francisco lets you "run the meter backwards" and put power back into the grid. That is how they are calculating 100% solar power since the amount you are sending in during the day offesets the amount you are pulling in during the evening. This also means that you don't need to worry about battery packs.

If you are already connected to the grid, then you can simply just feed the electricity back into the grid when over-producing (which is tracked by your meter), and then use electricity from the grid at night.

This actually works in your benefit if you have solar panels, because electricity prices are higher during the middle of the day (more demand). So you can "sell" daytime electricity (at high prices) [1], and then buy electricity at night which is much cheaper. This actually is the main benefit of the battery if you are connected to the grid, you can do the same thing.

1: You don't want to sell past your own consumption though otherwise you get paid very little for it

Except that, as pointed out above, the utilities only pay the wholesale rate for the electricity they buy back from you, and sell the overage to your neighbors for full price. Meanwhile, you're likely losing money selling your peak day electricity for 5 cents and buying it back for 15.

At least with PG&E, my understanding was that those rates only applied to a net over-production over a long period of time (I believe over the course of a year). As long as your power bill is not negative, any over-production during high value times of the day is sold at the market rate and offsets low value electricity you buy at night.

This is important with solar system sizing, because not only don't you want to be a net exporter of energy, the lower tiers of PG&E's energy rates are very cheap so you don't want to generate that power either. You really only want to offset the high-tier, high-demand electricity you use (or plan to use in the future).

For me it didn't really matter because my energy usage is highest during the peak times of the day, but this is my understanding of how it works. I'll know for sure in a couple of months when I see my bill :)

This is correct. Under Net-Metering policies in effect in California for systems installed now, you get reimbursed at full retail rates for every kWh you produce and export to the grid up to the level you import from the grid when solar is insufficient to need (at night, etc.) The wholesale rate is only for exported power generated beyond imported use.

Very few installations use batteries.

Right now in the Bay Area, almost everyone is using net energy metering (NEM). You get a bill once per year, and they balance out your usage vs generation, and any extra usage is charged.

There is a minimum you have to pay each year, so most installers aim for 85-95% of your usage to be generated by your system. As other folks have stated, it's not advantageous to sell back to the grid given the low price - as such, very very few people actually sell back to the grid, and instead make a small purchase each year, and mostly at off-peak rates.

Often, the most economical answer is heating a water heater rather than storing via a battery.

404 when accessed with Indian IP

Same even with a Canadian IP.

Also Mexico

Works fine here with a French IP address.

404 here, French IP address. (Free) :(

Same here, SFR.

same 404 when posting to facebook (where its spiders automatically extracts a title, blobs and images) where their server IPs are probably not all U.S. based. Weird.

404 from Norway

same with German IP

For those with 404 errors, it works if you add "?hl=en" at the end of the URL. https://www.google.com/get/sunroof?hl=en

Another take on this sort of thing: http://app.dumpark.com/sunlight/

The guys behind this apparently wanted to know the best place to go for a beer at any time of the day. They use the zenith of the sun, the surrounding landscape and the surrounding buildings and have it modeled throughout the year. I think they then realised there may be more useful ways to use this data.

Weird, it says it covers Boston but when I put my Boston address (single family in the city of Boston itself) it says they haven't reached the address yet.

I live just outside Boston and it worked for me (although it did consider my deck as part of my roof, which grossly inflated the estimate). Technically, they say "greater Boston area", so perhaps they don't actually include Boston itself.

Worked for me and my building is next to Copley. But Boston is very fragmented when it comes to service distribution—just see the broadband provider map:


I put in an address and it couldn't find it... Then I cleared it out and put in the address more slowly... When I did that I noticed that it found it in the drop down... so I selected it and THEN it worked... It seems like unless you put in EXACTLY what they have in the DB, it won't work... (in my case, I left off the "avenue" in my address).

I put in my Medford address and got results. I don't own, but it's still interesting to see.

Try http://www.mapdwell.com/en/boston . The City of Boston has already done a solar survey with the MIT spinoff MapDwell.

It's a 404.

same here.

Not available in Canada it seems

Currently only Fresno, Bay Area and Boston. The list of locations they have processed is not prominent and a bit washed out between the white lettering and the bright background image.

> Project Sunroof is currently helping people save with solar in the following cities: San Francisco Bay Area, Fresno CA and Greater Boston MA.

Not even available in most of the US.

It's a "start"

No, like, in Canada and Europe the site just returns 404.

They use 20 years and in the past I have heard that the average time for home ownership is typically 7 years. I don't know the true figure today (wasn't able to find it when I just searched) but for most people a 20 year payback is way to long and I would imagine this certainly contributed to lack of adoption of solar in addition to other factors obviously.

Edit: Note this: https://www.google.com/get/sunroof/faq/#financial-considerat...

It will raise your property value though.

Risks to getting solar power (according to Project Sunroof) are something to consider.

> As with any investment, there are some risks, though a well-installed system will make most risks extremely rare. Risks include PV systems catching fire, installations leading to roof leaks, theft, obsolescence, and hail damage and/or wind damage to the solar system itself.

> Fast-growing trees can shade solar installations, reducing production over time. Utilities can change how much they charge their customers for electricity, changing the savings from solar.

Here is a link that doesn't 404 :


Holy shit, Google is actually that idiotic/incompetent. 404s depending on its interpretation of my IP "location". From US (well, US IP that Google believes is in Hungary, because Google sucks as localization) it works, from other countries it doesn't.


So Google isn't trying to replicate Solar City, this is just an analysis tool if your home would be viable for solar panels. Almost like a middle-man for solar panel providers?

They are simply trying to reduce the resistance to solar energy adoption. If people can perform discovery and analysis in a fraction of the time, those who will benefit will more likely do it. Take a 10 hour process and reduce it to 30 minutes, for example. Same idea as a one-click checkout.

They're also trying to make money. Warm, qualified solar leads are worth hundreds or more.

A similar site with more geographical coverage, but less computer vision.


I was recently thinking about a project to show how easy it would be to power the entire US on solar panels. It actually wouldn't require much land, in fact if you put panels on every building top and parking lot you'd be almost there. What I was imagining was something that'd show you "ideal" spots for solar farms. Ideal meaning proximity to population centers, orientation of land, environmental impact, etc.

If you just paved over Edwards AFB with PV panels you'd have 50% of US electric energy demand, and that's assuming a relatively modest 6kWh per day per square meter.

Generating enough PV power for US electricity needs is easy. Covering a few square miles in Arizona with PV would do the trick. But storing and transmitting that electricity is damn difficult.

would be amazing to see sunroof and tesla power wall combine efforts on this...

How do they make these maps? Do they have satellite images of different points of (sunny) days and run the analysis that way?

Extrapolation. Use the time on the satellite photo to get the time reference, and thus where the sun is and how much sunlight going at a direction. Use the location and direction of the house get a sense of the facing of the roof. Use color level of the bright and shade sides to estimate the roof pitch incline. Given the roof's area, direction, and pitch, it's not hard to estimate the sun light received.

Far easier, they have 3D models of all the buildings already, as well as weather info. They just need to determine what is roof, and calculate the exposure.

Other than the "buy now" aspect, this doesn't seem any better for calculating solar savings than http://pvwatts.nrel.gov/ I used PVwatts when sizing my home system in Denver and thought it did a great job.

Hrmm, I don't know, the Google one seems more accurate in the details. It correctly shows my house as being plunged in darkness pretty much all day long (it's near the bottom of a slot canyon) whereas the site you linked above gives some quite rosy and unrealistic projections.

It's "easier." I just logged into PvWatts, knowing practically nothing about solar, and I'm confused at Step 2. There's a billion variables that it wants me to fill out instead of trying to calculate them for me for optimal results.

Agreed PVWatts is more accurate, and it's what a solar installer is actually likely to use when doing a roof assessment. But to use PVWatts you need to input things like the tilt and orientation of your roof, the size of the system you want to build, the cost of power from your provider, inverter efficiency, etc. This asks for your address and your monthly electricity bill to give you a rough estimate, both of which homeowners are much more likely to know.

They really need to get Florida mapped. Florida is a great candidate for solar power, but the state government is pretty clearly in the power utility's pocket and they work to make it very difficult for solar providers out here.

Wow. I can't believe how expensive solar panels are. This really is a great tool to give you an idea how much solar panels would cost. What about wind... does anyone know of any affordable residential wind turbine solutions?

Residential wind has some issues:

1) Performance - best performance is when the wind blows in a straight line, houses and other features will deflect it making it turbulent.

2) Noise - turbines are noisy, you're not likely to have neighbors appreciate it.

3) Mounting - Mounting one requires either a pole, or it can be mounted to the roof. However, roof mountings tend to cause issues (read damage) due to vibrations transferred through the mounting.

Not good for a residential neighborhood, but perhaps if you've got several acres of clear land?

Aren't there turbines with a vertical shaft, which don't need a large tower? I saw one a few months ago, built especially for city rooftops where you don't have that much space and generally need something not that expensive. You'd still have the problem of turbulences though (i.e. non-optimal performance generation)

Yes but vertical axis windmills take more ground space and make even more noise than their horizontal-axis counterparts.

under Solar City's finance model (and possibly others) payments on solar panels are less than buying the same amount of electricity off the grid. That includes maintenance on the panels for 30 years.

This is assuming you get adequate sunlight, which we do here in Denver.

This seems pretty cool, so any downsides I'm not seeing?

Agreed, this made my day. IMO only downside is that we don't have more of this sort of innovation happening at a smaller scale (akin to PG's recent tweet about the maturity of self driving cars relative to early versions of Google.

This could be the source of an interesting direct marking mail campaign by an enterprising solar installer. In the mailer you can list actual numbers.

Why are so many people in the USA live in individual houses rather than condominiums (apartments)? The latter is just so much more economical.

Because zoning codes mandate it: see The Rent is Too Damn High (http://www.amazon.com/Rent-Too-Damn-High-Matters-ebook/dp/B0...) and The Triumph of the City (http://www.amazon.com/Triumph-City-Greatest-Invention-Health...) for more.

The short version is this: Property owners now have shocking amounts of control over what their neighbors do with property. Owners, especially of single-family houses, elect officials who restrict development through zoning and similar means. Height limits and parking requirements effectively mandate single, detached housing in most of the U.S.

This only really got started in the 70s (see http://jakeseliger.com/2013/07/03/jane-jacobs-is-everywhere-...), and it didn't get really bad until the 2000s, when the shift back to cities ran into insane urban zoning rules to produce huge affordability crises. By now, most developers who dare to build condos or apartments have to build luxury apartments: http://www.wsj.com/articles/rents-rise-faster-for-midtier-ap... because that's the only way to make the economics work.

In the meantime, much of the population growth has shifted to Sun Belt cities in Texas, Arizona, Georgia, and Florida where development is easier and/or simply sprawls more.

Because it's more pleasant and we have the space and money.

If you want more economical, why not just have everyone live in barracks?

Because there's a lot of room in the US.

Seems also very similar to http://www.mapdwell.com/en

I live in Fresno, AKA, the surface of the sun. It says my yearly savings on a leased system is $2300! Wow. I may be installing solar soon!

What's the difference for you , between leasing and buying ?

I've seen a similar project where it lets you navigate to an address in google maps, shows the satellite image, then lets you draw an outline of your roof. (I can't remember if you had to estimate the roof angle or not.)

I wonder if this is this "not available" in many areas because Google is using machine vision to automatically compute roof metrics, or if it's because they don't have rebate & utility info for many markets.

Remember the 30% federal tax credit expires at the end of 2016. Only valid if you buy not lease your panels.

It seems to think my apartment building is a parking lot - there's no heat-map.

Link dead. . Google error. .

I'm also getting an error. Strange to see a google page down...

Not so. . Most of the old projects & not popular projects pages will be turned to an Error Page. .! But the comments here getting interesting. .!!

Anyone have any ideas on the computer vision techniques used here?

So how big of a business this could be for Google ?

Solar lead gen (and this is a very fancy form of lead gen) is a reasonable size business within greater lead gen industry, but I doubt this will be noted for the revenue potential in any of Alphabet earnings calls.

Dear Google, you make me feel really uncomfortable when you share a video with the world wherein you describe a project which you will make for "the country".

Do you really mean "uncomfortable"? I don't get it. Annoyed maybe? (like when new products don't come to Apps users)

OTOH, just because you have a generally accessible url, the video at that url must be addressed to the world?

No, i'm not annoyed. I understand why they can't offer it globally right from the start.

It's the wording itself that makes me feel uncomfortable in a way that is hard to articulate.

"The country", as if there aren't other countries. "For the country", as if it were a competition and this helps put our country ahead of all the others. As if it weren't for the customers, but for the institution of the nation.

Where does it say "the country" ?

Look for the youtube video. They say it at the end.


It hasn't reached most of the US either... Give it some time!

In most of Europe, the website just returns 404. This is like... the worst link ever.

I’d prefer if a mod would replace the URL with a link to either the About page or the video. Or to an archive.org cache of the site.

Linking to a site that 404's for almost everyone is inacceptable.

404 in Jamaica too - sloppy

in Asia 404 as well

It only works for three cities in the US as well.

My pg&e bills have never surpassed $50/month, so project sunroof convinced me that solar is not a good investment!

Fusion of maps, 3d modeling, electricity & lease rates, solar intensity, installers. Easy to use. This feels like something new and powerful.

For society: I wonder if it is safe for so much power to be concentrated in one organization.

As a technical accomplishment: I'm impressed.

But Google doesn't have power over electricity and lease rates or lists of installers -- they're just using publicly available data.

There are other sources for maps data, and many people have 3d modeling software.

So I'm not sure how this is "so much power" concentrated in one organization.

To me, what makes it powerful is the ubiquity - the 'full take' ness of it all. Sure the app is solar-related data, just for a few regions. But could include whatever data Google chooses, expanded to the whole world, for whatever audience Google chooses.

I've worked with aerial surveillance systems, the types used on police choppers. Put the crosshairs of the flir camera on a house and it will tell you all kinds of stuff: age/race of occupants, arrest records, warrants, tax status, etc. Amazing for LE, but a bit big-brotherly for my taste.

In the wrong hands, in the wrong circumstances, data fusion has incredible potential for abuse. IMHO. :-)

But if the data is already public, surely making it more widely available devalues it as a means of control or coercion?

You can blackmail me if you know something no one else does. You can't if you know something everyone else does.

Services like this fix asymmetric access to information. They're not revealing anything new.

Normal citizens do not have the ability to perform data-fusion like Google or a Government Agency. Services like Sunroof give just a tiny window into what they know about you. Hardly anything could be more asymmetric.

I believe the potential for abuse exists. Everything is fine now (here in California). But when the next crisis comes, data-fusion can be a powerful tool for authoritarians to control their opponents and suppress dissent.

> Normal citizens do not have the ability to perform data-fusion like Google or a Government Agency. Services like Sunroof give just a tiny window into what they know about you. Hardly anything could be more asymmetric.

If you're a normal citizen who has technical skills, yes, you can do exactly the same data extrapolation with publicly available datasources.

Well then - prove me wrong. Build a service like Sunroof, or like the surveillance app I described earlier in this thread.

Me noting that it can be done doesn't mean I'm going to waste my time building a similar app out while Google's service is still available.

Its not really new, and its not really powerful. From what I can see all this does is give you an estimate based on the square footage of your rooftop. There is a lot more that goes into a real estimate then how big your roof is, namely how can you arrange the panels to cover the roof. That is a neat trick and this company does that http://www.modsolar.net/

I worked with their stack for a bit and from my understanding their tool has been doing what this site does and then some extra stuff to actually get the panels installed.

And sun exposure.

> For society: I wonder if it is safe for so much power to be concentrated in one organization.

In general, it's probably not. But in this particular case it's been working very well for us so far.

I had a similar thought. I'd bet an "enter your address and Google will tell you your household political orientation" could probably be pretty accurate.

Shouldn't this be the "S" or "P" in Alphabet? Why is this a Google project?

Because its "Google Maps advertising", the project is to help Google Maps make a bit more money by selling solar installs via their tool. The "G" company is all about the advertising :-)

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