Many years ago I instrumented my house using a wireless network of 20 motes we had spare from a research project. One of my conclusions was that the house warmed up and cooled down quite a bit slower than I had assumed. Our heating at the time was on a timed thermostat. I ended up moving the "on" times 30 minutes earlier and the "off" times an hour earlier. We saved energy and had a more pleasant environment.
This was using dumb thermostat technology. If we were back later than usual, the house still got warm. If we stayed up later than normal, the house started to get chilly. Smart thermostats that know what you're doing can help even more, but the less predictable you are, the more the gains from the thermostat being linked to other systems to monitor what you're doing. If you're home the same time every day and go to bed at the same time, the gains will be less.
BTW, I also discovered that our dishwasher warmed the kitchen by 2C. The obvious conclusion was that it was best to use its timer to start it at 4am, so the waste heat has already warmed the kitchen by the time we're up for breakfast.
This was using dumb thermostat technology. If we were back later than usual, the house still got warm. If we stayed up later than normal, the house started to get chilly. Smart thermostats that know what you're doing can help even more, but the less predictable you are, the more the gains from the thermostat being linked to other systems to monitor what you're doing. If you're home the same time every day and go to bed at the same time, the gains will be less.
BTW, I also discovered that our dishwasher warmed the kitchen by 2C. The obvious conclusion was that it was best to use its timer to start it at 4am, so the waste heat has already warmed the kitchen by the time we're up for breakfast.