Imagine thousands of households doing something smarter.
A couple of hours after 6pm and a couple of hours just before you wake up. All controlled from a simple timer.
Yes, Nest would be a fancier solution, but I don't really see much benefit a part from the 'coolness' factor.
I guess Nest is heading towards this direction, but pre-warming a house very "first-world".
Imagine a neighborhood of 100 homes where you know all 100 people will return approximately at 6pm in the winter, and they all want 72 degrees. Taking into account the insulation of each home, if you could pre-heat the homes on a rolling schedule (say, heat 25 of them to 75 degrees at 3pm, accounting for 1 degree of heat dissipation per hour, heat another 25 to 74 degrees at 4pm, etc.), you will actually in aggregate save a lot of energy and cost because of inefficiencies in the way we deliver and generate energy during peak times.
(@yitchelle - central data center)
Especially given that this works best for second homes like a weekend house in Tahoe where it might take a full day to warm up if you left the heat off all week.
A simple, programmable thermostat will make up for the purchase within the first year of service.
While there is no momentum in heat transfer, the walls of your house store heat. If you're away long enough to allow your house to cool down it will take more fuel than it would to keep it at a reasonable temperature. Also, this is much, much more comfortable than to arrive in a stone cold house, only to open a window 30 minutes later because of the blazing heat.
I'm not saying it's always better to keep a certain temperature, though. It depends on the time that you're away, the insulation of your house, the outside temperature, the efficiency of your boiler, etcetera. But, having lived in houses with ordinary thermostats and non-modulating boilers and houses with programmable thermostats and modulating boilers I can tell you this: I'm not going back to the old stuff. The indoor climate is so much better now!
My otherwise boring furnace is variable speed and the longer its on, the faster it runs. It's really roaring after about 30 minutes. Its more than a decade old, this is pretty old COTS tech. My first zillion BTU cost me somewhat less than my last zillion BTU in any heating cycle.
I live in a cold northern climate with great insulation and low heating bills and a variable speed furnace and the house is basically never empty (spouse and I work at home often enough, etc). The whole "nest" idea doesn't work financially for me although it is interesting to watch.