I looked into the nest but I don't think it would save me any energy. And I'm wondering if that's actually true for lots of people.
I have a modulating (i.e. change flame level) condensing boiler (the highest efficiency available). I programmed it to run as close to 24/7 as I could, because that way it uses the lowest flame, which is the most efficient flame.
When I tried a setback thermostat when the boiler attempted to rewarm the house it shifted to a higher and therefor less efficient flame. So I gave up on that and let it run on low all the time. So there would be no peak usage by me.
As people shift to more efficient ways to heating I suspect that this will happen to everyone. Not just modulating boilers, but also multi-stage heating with a heat pump. By trying to rapidly heat the home you can't use the heat pump.
It's also true with an A/C - the faster you are trying to cool the larger temperature gradient you need, and therefor you lose efficiency.
It's also true with an A/C - the faster you are trying to cool the larger temperature gradient you need, and therefor you lose efficiency.
I'm not sure that's always correct. The Coefficient of Performance (heat moved/work done, higher COP is better) of an A/C is:
COP = T_hot / (T_hot - T_cold).
T_cold is the inside temp, T_hot is outside of the heat exchanger. The narrow the temperature range, the better the COP. Thus the A/C will actually be more efficient in terms of heat moved per watt while it's cooling a warm house down than when it's already cool.
There's one other factor that applies. The rate of heat transferring into the house is proportional to the temperature difference. Once the house has warmed up, you reach equilibrium. The net heat flow stops, so the total amount of energy you need to remove later stops rising. If you run the A/C all the time, heat is transferring in all the time. So the total amount of heat you need to move back outside in a day increases significantly if you leave the A/C on.
> I programmed it to run as close to 24/7 as I could, because that way it uses the lowest flame, which is the most efficient flame.
The energy loss from your home increases as the differential between inside and outside increases, right? So at night or when you're out, if your house were kept colder, then you'd lose less energy to the outside.
So by keeping your heating running 24/7, you're wasting some energy in the extra energy loss when you're out, right?
How does this compare to the efficiency gain by running your more efficient flame? Have you calculated or measured that you actually save energy overall?
I have a modulating (i.e. change flame level) condensing boiler (the highest efficiency available). I programmed it to run as close to 24/7 as I could, because that way it uses the lowest flame, which is the most efficient flame.
When I tried a setback thermostat when the boiler attempted to rewarm the house it shifted to a higher and therefor less efficient flame. So I gave up on that and let it run on low all the time. So there would be no peak usage by me.
As people shift to more efficient ways to heating I suspect that this will happen to everyone. Not just modulating boilers, but also multi-stage heating with a heat pump. By trying to rapidly heat the home you can't use the heat pump.
It's also true with an A/C - the faster you are trying to cool the larger temperature gradient you need, and therefor you lose efficiency.
If I'm wrong here I would be happy to be corrected, but the US Government seems to agree with me: https://www.energystar.gov/index.cfm?c=archives.thermostats_...