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IoTaWatt Open Source WiFi Electric Power Monitor (iotawatt.com)
172 points by mrep 3 months ago | hide | past | favorite | 82 comments

Just an FYI that your home may already have a grid-connected meter outside, and it may already have a wireless interface.

For example, if you're a ComEd customer in the Chicago area, your smart meter is Zigbee-enabled and works with a handful of approved devices:


The information won't be as finely detailed since it's not sensing every circuit in the home, but for $70 and no tinkering necessary I can read my home's consumption in XML format every 10 seconds.

And some power meters have IR-based interfaces. A "blink every X Wh of energy used" LED is quite common, but some also have bidirectional IR interfaces, recognizable by a metal circle with two lenses at the front (read heads are magnetic and simply set on the metal plate). (might be a European thing though)

AEP Ohio ended their program last year. But before that, they even went as far as sending out freebie Wifi-connected Zigbee bridges to interface the meter before the program went tits-up.

Now that there are zero applications for it, it's about as useful as a dumb meter.


Yeah this was in part because of H.B. 6 the nuclear bailout which is also related to one of the biggest bribery scandals in Ohio politics. The smart meters were mandated by the energy efficiency aspects of the renewable energy provisions that were stripped out so that they could give money to make nuclear energy and coal power plants stay on-line. They cut the renewable energy goals and energy efficiency provisions so they could pretend like they were saving consumers money by giving the $ directly to the nuclear plant owners. Of course most of this is on-hold right now due to the 60 million dollar kickback and court injunctions but so far the legislature doesn't seem likely to restore the energy efficiency aspects. The utility companies still benefit from real time monitoring of their customers and remote cut-off but I guess there is no way to interface with the meter directly now.

And even meters that don't have zigbee might be readable using an RTL-SDR. You do have to figure out which one is yours and which are your neighbors, though.

Pretty sure that the datastream is encrypted. Being able to sniff your neighbor's power consumption from far away is a pretty large security hole.

At least the ones I have seen are not. I am able to read the all the power meters in my building with a cheap USB SDR and this software.


I have not gotten around to figuring out which one is mine or a good way to system to store/display the data but I certainly can read the date.

In the grand scheme of things it is a minor to medium security flaw, power usage could be used to infer which houses contain valuable items and when people are home. I'd say medium at most since a lot of other things Visible curbside indicate this as well (lights, cars in the driveway, etc.). On the other hand, electronics are pretty efficient. A wealthy house with all the lights on is still using less electricity than a small apartment using an electric stove. But I guess if you were really interested in stealing electric cars then it would be really useful.

I imagine it depends on location, but there are places where it's wide open.

"Using a cheap RTL-SDR, it didn’t take long for [k-roy] to tap into this transmission and stumbled across the power readings for his entire neighborhood using a simple command"


Sometimes they are. I gave up on playing with my water meters because of it; my RTL-SDR can pick them, alright, but I checked the manufacturer docs, and the meters encrypt the datastream.

As was pointed out, you still have to figure out which signal comes from which meter, so unless you find a way to tag them all, they’re anonymous.

You've just made me run outside to check my meter. What do you use to read it and are you happy with it?

Rainforest Automation device, see below.

Am I happy with it? Good question. I dropped RRTP last summer so I'm not as involved with it anymore. It doesn't really tell me much that I don't know, I suppose.

Which device do you have that gives xml output?

Rainforest RAVEn USB. It looks like an FTDI-type serial port to a host. If you skip their application and just open the port it constantly sends data.


Might be discontinued now, but I think Rainforest's gateway product is a continuation.

The OpenEnergyMonitor emonPi has been around a while and also quite good, and supports MQTT which I don't think IoTaWatt does.

https://guide.openenergymonitor.org/technical/emonpi/ https://openenergymonitor.org

[edit] I see it can use EmonCMS which is part of the OpenEnergyMonitor project.

Have you seen any good mods for emonPi that increases the number of sensors? I really want to monitor every circuit in my panel (40)

Also would be interested in this. I've looked but haven't found anything that has 2 voltage inputs (for split-phase) and 20-40 current inputs. Tempted to build it myself, basically this[0], pared-down, pluggable into a common backplane that would have ethernet, but haven't got around to it yet.

[0] https://github.com/CircuitSetup/Split-Single-Phase-Energy-Me...

I bought a Sense (https://sense.com) because I loved the idea of applying ML to my energy consumption. While the interface is nice, it just hasn't lived up to its promise. It wants to classify 40% of my energy usage as 'unknown'. Nothing so insightful that it's really worth giving up my privacy, unfortunately.

The future of IoT is open, hackable, and decentralized. The IoTaWatt looks like a big step in the right direction.

How in the world can ML benefit energy consumption?

A cynical person would say "Through smartly-targeted ads for devices claiming to use less power than the ones you have" but I'm totally not one of those people.

It doesn’t benefit it, it is used to infer the consumption by each of the devices in the circuit separately. In theory, in practice it doesn’t really work well, as Op pointed out.

It really is a pretty good device - I have 14 of them in my install:


(post 737 has the iotawatt details)

I have been running this setup since October with great results.

Wow. That's a substation! I'm honestly surprised that wireless works so well, at those levels I'd be very tempted to use industrial controllers that are all hardwired.

Agreed - in fact I did run Cat6 to all of those locations with the assumption of needing a direct connection. The IotaWatt doesn't have an ethernet interface, so wireless is the only way to connect. I have APs in most of the rooms (Using Ubiquity APs), so coverage is very good. I was concerned about the devices being in a sealed metal box, but wifi is surprisingly robust!

It is possible in the future I might switch to something else, but the units have been working really well without any glitches.

For those building their new homes right now, or updating the electrics, Schneider, Leviton and LeGrand have smart circuit breakers in their offer, which not only measure the consumption, but offer additional monitoring, like the load or tripping. With LeGrand you can even trip them remotely, which, combined with leak or fire sensors, can definitely save money – or even lives.

LeGrand has an open API and is not cloud-based. Leviton, last time o checked, was cloud only.

The cost is surprisingly low, too (compared to what you might expect).

I'm not well-versed in this field but had heard of the Sense, and was almost going to buy one, except I detest that it's closed off to everything but the cloud. Furthermore, I've heard the mains-only monitoring it uses, while trying to divine the power sinks by their signature, leaves much to be desired. This looks like just the thing for me.

Out of curiosity, do you plan to add a sensor to every output breaker in your box?

I'm interested in a closed (for everyone but ME) system as well. I'm not sure I'll be able to fit much hardware in the breaker box so I'm unsure.

If this is possible, I know my breaker box has enough room, but is there any risk with all those cables with the 3.5mm end causing arcing?

How do you route them out of the box? Should the wires criss-cross? Bundle them?

Leave everything in the breaker box and communicate out with wireless or optically isolated connectors.

You still have to plug in two wall wart style transformers (one is for reference voltage, the other is to power the box) into a real power outlet outside the box, and then get those wires inside the box. Or commit some electrical code sins and wire that inside the box too.

Many houses have a doorbell transformer mounted on their service panel with no plug; I can’t see how that’s a NEC violation (and therefore providing a path for a similarly engineered, code-compliant solution).

Yes, I have seen this, but it is unusual, and the doorbell transformer is still outputting AC, not DC, but at a lower voltage, and that output is not run inside the breakerbox.

I've been considering an Emporia Vue 2 for a while now. It would end up being about half the price of this. Does anyone know anything about it? I'd like to go open source, but my primary motivation is lowering power costs, so its hard to justify doubling my ROI time.

I started using the Emporia Vue 2 about a month ago. Overall I'd say it's great. I hooked up a few circuits individually and I got crucial insight into unusually high energy usage from a heat pump + air handler + auxiliary heater setup.

I much prefer this approach (by Emporia and IoTaWatt) of multiple CTs (non-contact sensors applied to specific circuits) vs. the "Learning" devices that try to interpret what's using energy based on a signature of power usage, with reportedly very poor success.

The app is quit useful. I do wish I could get access to the raw data by default, without needing to send it through their cloud first (only way to get data off the decice) and submit an export request to get emailed a CSV.

I've been thinking about getting and Emporia and searching around I saw that there's a project on github to extract data using Python.


I have no idea if it works, but it might be worth taking a look.

Was installation difficult?

The concept of installation was very simple – just put clips on wires.

However even with my entire electrical panel switched off at the main breaker, the supply from the meter is always live. So with the panel cover removed in order to install the clips, it would have been possible to touch the supply lines and get a lethal shock.

If you have any qualms about working safely in an electrical panel, hiring an electrician is the way to go.

Dumb question:

What do you do with this information? I can see it being useful for detecting anomalies, but for every day usage... I am not going to stop using my refrigerator to save power.

I learned that the radiant heat in the bathroom floor used very little electricity compared to heavy-hitter circuits like hot water, so it wasn’t worth adjusting the thermostat schedules and give up comfort.

We use it to keep an eye on how much energy we use for grow lights in the greenhouse.

As a bonus, the electricity usage of the well pump is a proxy for water level in the well.

I track my usage with the tesla powerwall unofficial api and have since learned not to worry about my fridge, it's my dryer that really eats up all the power (and my furnace fan). Also realized leaving my lights on vs off doesn't change my usage at all so I'm not worried about turning them off like I used to.

Beauty of leds lighting I assume?

The real cost comes from when they're on for too long, generating a lot of sustained heat, or when the DC power supply stops working. Would love for PoE-based lights to take off for residential use but that's probably a pipe dream.

Yea the only issue I have with led is some are really finicky with frequency changes. The ones in my kitchen will flicker when the power wall is full. I haven’t gotten around to asking Tesla to adjust the frequency though.

Hmm haven't run into that problem. How frequent does that happen?

Ubiquity is bullish on PoE lighting.

I used to work on the home energy monitoring space a decade ago. The most useful thing I ever heard of as a result of home electricity monitoring is that someone found a 100-W bulb that was always on.

If you have it connected to a major electricity consuming appliance, like a refrigerator, an electric dryer, or a furnace (whose fans use a ton of electricity), then in theory you can see any degradation in efficiency over time which may indicate that they need repairs. I doubt most people will do that.

For example, I'm pretty nerdy about energy use, and it took me 2 years to notice that the output of my house PV system had reduced 30% because of some trees that had grown taller.

Also, in the future, this sort of monitoring will likely be built into the appliances themselves.

There are also easier ways to achieve something like this, for example kill-a-watt meters.

every day usage: If you also have a PV system you can decide when to run the dish washer, laundry machine, dryer, ... and how many of these "bursty" appliances can possibly run in parallel w/o consuming energy from the grid

analysis/optimize energy consumption, e.g.:

* we moved the freezer from the kitchen to the basement instead of buying a more energy efficient new one

* the pump in our (20yrs old) heating system constantly uses 60W -> the whole furnace is now due for replacement

* determine your electricity base load in order to make an informed decision about the capacity of a battery system that buffers energy demand during the times the PV system does not supply energy

I'd say the real value is in looking into long term patterns (no ML needed).

I don't know about residential. Seems mostly to be a plaything.

But there is big potential for this in industrial settings. Imagine being able to monitor machine uptime around the clock by sensing amperage usage.

Tracking cycle time by counting cyclic spikes in current and putting it on a live dashboard.

Detecting motor degradation by sensing increases in amperage required over time.

Calculating energy consumption per pound of commodity part produced.

Like many people, our house is on a time-of-use plan. This kind of monitoring is useful to determine if there are loads that could be cheaper to shift to a different time of day.

This is for the same kind of people who record their heart rate every minute for their entire lifetime... And then proceed to do nothing with the mostly-useless data.

InfluxDB integration? Mains, branches and my solar inverter? If I had 3-phase, it would do that too?!

Very slick! I've ordered one.

I installed it last year. Very happy.

How many clamps are you using?

I'm using all the 14 inputs.

I wonder about the choice of 3.5mm TRS stereo jack for the inputs.

Ordinarily this would mean you need to buy prefabricated 3.5mm TRS cables and cut one end off to wire them up to the CT, because it's difficult or annoying to terminate your own 3.5mm TRS plug connector.

Why not some other connector choice? Maybe RJ11, or one of the typical 'green' two conductor terminal blocks socket/plug combos with latches you can get from Digikey or Mouser?

I haven't had tools to do 6P4C for over a decade and almost never used them anyway, but my soldering iron works great for TRS. I'm not displeased with this connector choice.

FYI, there are 3.5mm TRS adapters out there that have green screw terminals if that's your thing. They're very inexpensive.

But connecting my own current transformers isn't the intent here, I don't think. I think the intent is to have plug-and-play kits that are hard to screw up.

And the prices for their own CTs seem fine to me.

All these current sense coils come with 3.5mm so I think thats why they use them.

High quality CTs from reputable brands come with wire leads. Here’s a nice, inexpensive CT, UL listed:


This style also has an integrated burden resistor, which makes it far safer than a plain current transformer.

Oooh, I've been wanting something like this for some time. Prior searches have only turned up systems far, far larger and more complex than a house needs.

Super cool stuff, anyone who's dug into this know how the integration for the actual measurement works? Would it be possible to use with some shunts or hall effect sensors for DC applications with a little electrical shoehorning? I run about half my stuff off DC directly for increased efficiency and save that this would be perfect.

Does anyone have experience how hard it is to add something like this to an existing EU breaker panel? I'd love to have this but, since I'm living in a rented flat, I'm not very optimistic about being able to retrofit it.

I’d say not easy: in EU we build around the circuit breakers, while in the US it’s common to use a standardized front panel that, when removed, will give access to the circuitry behind the breakers. I have yet to see a house without it. And I notice, because they always stick out like a sore thumb.

Thank you for chiming in. My circuit breaker box is in the wall as well, but it seems possible to take off the cover. Maybe there is enough space behind it.

I guess space is one issue, the other one is if you have access to each breaker's circuitry?

I would be considerably more likely to buy this if there was a wired Ethernet version.

One option for you might be the Brultech GreenEye monitor. They are considerably more expensive and unless they've changed a bit more of a roll-your-own on the coding side.

I literally installed this last week. It's awesome to monitor individual circuits and track with awesome detail what's using electricity. Yup... a hot tub in winter SUCKS.

Other than that... easy install, great instructions.

Is there anything simpler/cheaper that can go into a wall socket and be queried over bluetooth? (or join an existing wifi network)

All you can measure by plugging into a wall socket is (1) voltage; (2) power, but only for devices plugged into that outlet (by installing a meter like a kill-a-watt between the outlet and the device).

In order to determine power consumption for an entire circuit, or your entire house, you need to put a sensor around a wire in the breaker box. You can’t even do it in the walls because once power cabling leaves your breaker box, all the conductors for a given circuit are bundled, and if you put a current transformer around that bundle, it will show net zero power because it’s summing both halves of the AC wave.

You need to get a sensor around just the hot wire of the circuit, which is only accessible on its own inside the breaker box.

There are a lot* of cheap 2.4Ghz wireless outlets that can be flashed with custom firmware that supports power usage & outlet control over MQTT & other protocols. Keep in mind that these devices have to be manually configured & calibrated.


* Some new versions of these outlets come with firmware that can not be patched/flashed so do some research.

Also most of these are limited to 10 amps of restive load... inductive loads like motors, compressors, and to an extent power supplies, will have peak loads 3-4x there 'real' consumption which can damage the relay if its not rated for the high initial load. If anyone knows of a cheap alternative or cheap DIY that can handle +20A I would be very interested as it would be nice to be able to control things like fridges without worrying the outlet will fail closed & my food will spoil.

I picked up one of these a month or two ago. It works really well, quite simple to set up and has not gone down yet.

0.5% accuracy on those CT's if Alibaba led me correctly - that's revenue grade, nice!

The numbers I get from mine match the power company’s daily numbers almost perfectly.

Would love to know if there's a docker [compose] setup for the influxDB+grafana setup.

DIN rail mounting would be nice. Is it not used in U.S?

Nice, its ~$10 in hardware for all that functionality.

IotaWatt is amazing!

Wow, this is slick!

Looks nice, sad that there is no 3-phase version

It works with three phase.

There are two ways to do it.

Either, one clamp, and it calculates the other two, or you can use three clamps.

cool need to integrate this

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