My wife and I have a monthly debate about whether our @nest thermostat uses more/less energy. My argument has always been: probably a null effect, but it's fun technology. Her argument: we're spending more money on this toy and our bills seem higher. [1/n]
Her argument is fair, but I've contended that our monthly Home Report from @nest simply makes our electricity consumption more salient (see, e.g., rff.org/research/publi…) [2/n]
So, I pulled our historical hourly data from @pepco and plotted the results: [3/n] 
I find it hilarious that we peak during the winter between xmas and the @ASSAMeeting, typically when we're working from home and winter has just set in. [4/n]
Context: we live in a small 1BR apartment in DC, electric heat, central air. Prior to our smart thermostat, we've had a dumb one. [5/n]
After controlling for max daily temp and humidity, presence of rain, and absorbing month and day-of-week FEs, our residual electricity consumption looks pretty flat before and after our thermostat replacement. [6/n]
Add in a dummy for whether we had our smart thermostat installed, we can look at its impact on our daily electricity (in kwh). Results suggest that the @nest thermostat increased our energy consumption by ~1.5 kwh/day, but the effect is statistically zero. [7/n]
if you're worried that electricity consumption is distribution log-normally, I got you... magnitude is large (~5% increase in consumption), but not significantly different from zero [8/n]
...and the effect holds up if we use only the months for which we have pre-smart thermostat data. [9/n]
For those p-value hawks out there, recall this is an n=1 and I'd like to think that we're a fairly select sample 😎. [10/n]
Working title: "Do smart thermostats save energy? Evidence from artisanal data" [11/n]
It's easy to joke, but these thermostats sell for $250 a pop claiming energy conservation and I've seen ZERO pieces of causal evidence that they actually save energy, and there are good arguments for why usage might go up. [12/n]
I like my thermostat, but not because I think it saves me energy. Sorry to be harsh, @Nest, but if you want to claim energy savings, prove it. I know an economist or two who'd be happy to partner with you to run some experiments 😉 [n/n]
At this point, it’s worth re-emphasizing the point of econometrics: we use sample data to infer what’s going on in a more general population. My electricity use is not representative and should not be used as evidence of whether smart thermostats work in general [(n+2)/2]
But it’s also worth emphasizing that I have not seen large-scale, *causal* evidence in one direction or the other. So, I’ll keep wearing my economist hat of “zero until proven otherwise.” [(n+3)/n]
