You may have heard that there is a solar eclipse crossing the US on Monday, which will block out the sun for a couple of minutes. This is happening at a time when shockingly, America has become dependent on solar power instead of good old reliable coal that would just laugh at an eclipse. Instead, according to Bloomberg, as many as 9,000 megawatts of solar power may be knocked offline. Bloomberg claims that it’s “the equivalent of about nine nuclear reactors” or to put that into even more graphic perspective, the equivalent of 4 billion AA batteries.

But the Nest thermostat comes to the rescue. It already partners with utilities to dial back the AC at periods of peak demand with what they call their “rush hour rewards” program.

The upcoming eclipse represents an opportunity for a special energy rush hour. Instead of being caused by high demand, this rush hour will result from a temporary reduction in the clean energy supply. During the eclipse, as less light reaches solar panels across the US, solar energy production will drop, meaning more power plants may have to be fired up to cover the shortfall for just a brief time.



If you join the Eclipse Rush Hour program, the thermostat will actually crank up the AC a few hours before the eclipse and pre-cool your home; then it will turn it off during the eclipse to reduce the spike in demand on the conventional power sources, and then return to its normal schedule. “Your Nest Thermostat won’t let your home get too warm.”

This raises some very interesting issues. There is no question that having the Nest turn off millions of air conditioners to shave the peak demand as the eclipse passes over makes a lot of sense, and might make a real difference. But turning up the AC to pre-cool the house so that it “won’t let your house get too warm”? How leaky and badly insulated are American houses, that they might get too warm in an eclipse that lasts two minutes and forty seconds?

Of course, the effect of the eclipse covers a larger area so the Nest will probably turn off the AC for a longer period than just the period of local totality. But it doesn’t change the basic story. I have written before that in a properly built and insulated house, a smart thermostat would be bored stupid, with nothing to do. It’s why I am such a big fan of Passive House, the standard of super-insulation and sealing that makes a house or building resilient.

Passive Houses will be laughing at the eclipse on Monday; the sun could be blotted out for days and they wouldn’t really notice. The eclipse provides yet another example of why we need radical building efficiency before we need solar panels and smart tech. It’s a teaching two and a half moments.

Nest-owning TreeHugger Sami has disagreed with me, writing:

We all know we should seal drafts, install insulation and put up a washing line—all too often, however, we don't. By providing an attractive, fashionable (and yes, expensive) first step on the path to energy efficiency, smart thermostats may act as a gateway drug.



I’m sorry, Sami, but if your house is so bad that it is going to get too warm in this short a period of time, then it needs a hell of a lot more than a smart thermostat.