What is the best thermostat setting for max electric bill savings during summer time?
Wednesday, May 5th, 2010 at
5:25 pm
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During the energy crisis of the 1970s, the government suggested that you set your AC thermostat to 80 and your furnace to 68.
I don’t know if anyone has ever really proven which is more cost/energy efficient, leaving your AC set to some higher temperature during the day when you’re not home and turning it to the desired setting when you do get home, or turning it off completely when you’re not home and just turning it on to the desired temperature when you get home.
I would think that it’s the latter (turning it off completely when not home and turning it on to the desired temperature when you get home). One of the reasons an on-demand water heater is so much more efficient that a tank water heater is that the tank heater stores an amount of hot water all the time, even when you’re not using it. The on-demand heater just heats the water when you use it.
Thinking in terms of your house and AC, when it’s on during the day, it will still be using a lot of energy keeping the house at some higher setting (like keeping a tank full of water at a higher temperature). As opposed to turning it off completely, where it uses absolutely no energy. I would think it would take less energy to bring the temperature down to the desired temperature with the AC being off all day than it would to keep the house at some temperature all day and then bring it down a bit more to get to the desired temperature.
Since the only criterion you gave was to minimize your electric bill (i.e., maximize savings), then the answer has to be, turn the A/C off and leave it off.
My guess would be that you have some other requirements that you haven’t told us about (e.g., you don’t want to lay awake in bed, sweating all night.) Here’s the deal. The higher (warmer) you set the thermostat, the less electricity your A/C will use. You will have to decide for yourself how much heat you can take, and how much comfort you are willing to pay for.
As for leaving the house with the A/C off. That’s going to depend on two things. (1) What’s in your house that might be harmed by high temperatures? E.g., pets, plants, electronic equipment (especially if you leave a computer running while you are away). And (2) how long does it take your A/C to cool the house back down to a tolerable temperature once you get home?
The answer to (2) is going to depend on how hot your house gets while you are away, and how big your A/C is. Again, you will have to determine by experimenting, what "away" setting of the thermostat is right for you.