Writing in his ever popular Energy Vanguard blog, Allison Bailes examines a number of studies - one in Oregon, two in Indiana and a white paper by Google-owned Nest - and provides an answer about whether the $250 "smart" thermostat can actually save energy.
According to Allison it can save on heating energy with both gas furnaces and heat pumps, and can save on cooling with air conditioners and heat pumps. And as we can expect from our favorite physicist, he is super thorough in his analysis (but still delivers a clear answer):
One important thing to point out here is that the Oregon and Indiana studies used carefully chosen participants, and they installed the Nest thermostats for them. One question that comes up with Nest data sometimes is, what is the effect of having self-selected gadget-geeks or energy savers on the savings data? In those three studies, that's a moot point. It seems that the average Nest owner will save energy even when they're not the kind of people who would go out and buy one on their own.