

Global Cities Ranked by Time Spent in Optimal Temperature Range (Click Headers) - bromley
http://online.wsj.com/article/SB10001424052702303302504577325612586019258.html#articleTabs%3Dinteractive

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bromley
My company came up with this data for the Wall Street Journal, so I should
explain that the title here is a bit of an over-simplification.

The main point is that if you sort in ascending order on e.g. the "Average
number of degrees temperature deviates from 60-80 range in last five years"
column you should have a good indication of how the cities compare in terms of
the time and extent to which their air temperature deviates from a comfortable
range.

But if you're interested in more detail, the figures in that column are
actually derived from:

\- The heating degree days (HDD) with a base temperature of 60 F summed for
each day over the last 5 years (measuring the time and extent to which the
temperature dropped below 60 F in that 5-year period).

\- The cooling degree days (CDD) with a base temperature of 80 F summed for
each day over the last 5 years (measuring the time and extent to which the
temperature rose above 80 F in that 5-year period).

We summed the HDD and CDD together to get a relative measure of how much and
for how long the temperature was outside the optimal range over the 5-year
period. Then we divided by the number of days in that 5-year period to get the
total degree days per day. The day bits cancelled out, effectively giving the
average number of degrees that the temperature deviated from the optimal
range. (I think the WSJ sensibly thought that expressing the data in terms of
average temperature deviation would make it more accessible than if it were
expressed in terms of degree days, which most people probably aren't familiar
with.)

We did that calculation for each of the 66 "global cities" listed in the 2012
list that you can find on Wikipedia at
<http://en.wikipedia.org/wiki/Global_city>

Anyway, irrespective of whether the meaning of the figures themselves is
intuitive, I think they're ideal for ranking the cities in terms of how
favourable their climates are in terms of temperature.

The main body article also has some interesting discussion of the ins and outs
of using temperature as a measure of a given location's comfort levels.

Probably of more interest to me than most as I'm quite chuffed that my
company's data was used in the WSJ :) But putting my shallow ego aside I do
think the numbers are cool as I've long been intrigued by the idea of finding
the locations on earth with the perfect climates.

~~~
schiffern
I see you just launched an API. Looks like you're working off a dump of WU's
data? Nice dataset there.

For the back-of-the-envelope calculations I always do, I would probably just
write a script to scrape WU's data myself and do the HDD/CDD calculations
manually. It's a shame that there's no free trial of your data (~50
request/day or similar). It would make me far more likely to fall in love with
your API. Then, on the not-inconceivable chance that I write energy software
in the near-future, I would be far more likely to query your API instead of
rolling my own solution.

I definitely agree with you that we need to bring more computation to energy.
I'm gifting someone a Nest thermostat later today, which embodies the kind of
innovation we need. The fact that the Nest is considered as innovative as it
is shows just how lacking we've been in this area. It's just an Android on the
wall, after all!

Thanks for posting. I take it info@energyauditsoftware.com reaches you?

~~~
bromley
Thanks for your thoughts there! Yes we are working off of WU's data. They have
an awesome database of weather data and they've been very kind in allowing us
to use the temperature part of it for our degree days system.

We do have a free API trial actually, though it's limited in the sense that
you can only get data for the Cape Cod area:
<http://www.degreedays.net/api/test>

We'll happily give most people a full free trial if they ask. We don't offer
that publicly, partly because a lot of people are just looking to assemble a
database of 5-year-average data and then quit, and partly because the number
crunching to calculate degree days properly is pretty expensive so we have to
be careful about watching our costs. A proper free tier could kill us,
particularly if a manufacturer of popular installable energy-related hardware
or software decided to wire things up so all their customers fetched degree
days from our system whether they wanted them or not.

But perhaps we should re-consider the current setup for trials... We only
launched the API recently so at the moment we're still playing it by ear
somewhat.

If you mention "bromley" in an email to that address or just email info at
degree days dot net it'll get through to me - and I'd love to hear from you or
anyone else developing software for energy-related applications.

~~~
schiffern
>particularly if a manufacturer of popular installable energy-related hardware
or software decided to wire things up so all their customers fetched degree
days from our system whether they wanted them or not.

I always check the TOS of any "public" API I use, and I suspect most
developers are the same. Perhaps this could be mitigated by some carefully-
worded clauses? If someone does it anyway, you could protect yourself by
blacklisting their API key for TOS violation.

We should continue this over email.

~~~
bromley
It's possible that could work. Our current testing API is rate limited only on
IP address but if we required a sign-up we'd have more options. A free tier
couldn't go too far out of control if we could stop taking new sign-ups at any
time.

But at the same time we already have a full free tier in the sense that anyone
can download free data from the website. At the moment we're seeing the API
purely as something for those that want more data than the website practically
allows. My hunch is that it's probably best to keep the API paid only... Free
accounts with really low rate limits would be frustrating for the people using
them (as they'd hit their rate limit all the time) and would just increase our
support costs. In the end we'd have to increase the costs of new paid accounts
to support them, which is not something I'd want to do.

Never say never though... My thoughts on that could change over time as we get
more customers and feedback.

I got your email, thanks, will get back to you shortly :)

------
michaelochurch
My problem with this is that I think degrees over are much worse, and humidity
is also such a major factor in temperatures over 80. 85 and dry is perfect; 85
and humid is miserable. Also, with typical NYC humidity, 90 is _a lot_ worse
than 50 (assuming you have access to appropriate clothing). You don't want to
do anything outdoors in NYC 90 unless you know what you're doing, whereas
biking or running in 50 is pretty easy. NYC 90 is equivalent to 35, and 100 is
equivalent to 10.

~~~
bromley
These are fair concerns. The journalist just wrote a related blog post at
<http://blogs.wsj.com/numbersguy/modern-thermometers-1132/> that discusses the
"experience" of temperature more.

An improvement on the analysis might be to adjust all the temperatures for
humidity and wind speed etc. before calculating the deviations below 60 F and
above 80 F. My company's system doesn't do that because those other factors
are much less important for energy consumption calculations (which is what
degree days are traditionally used for). But I think they probably would be
good factors to include for a more thorough analysis of human comfort. (I say
"probably" because the complexity would increase considerably and also the
figures would become less clearly defined in a sense as well. So it wouldn't
be 100% positive.)

