Deos it save energy to turn your thermostat up/down if you're leaving for 12 hours or less?

Question

Sorry, I meant DOES

Answer 1

It definitely saves energy.  To keep it simple I'll explain what happens in the winter. Heat loss is directly related to the difference between the inside and outside temperatures. If you turn off your heat when you leave the house the rate of heat loss decreases. For example, if it's 40*F outside and 70*F inside more heat (and therefore more energy) will be lost compared to having an inside temperature of 60*F.

The common argument against this strategy is that it will take more energy to reheat the house once you come home, so it is better to just leave the heat on.  Think of it this way:  your heater is replacing heat that is lost to the outside.  If you turn off your heat and let your house cool down there is less heat energy to be lost.  Less energy lost means less energy spent keeping the house warm.  You can test this by timing how much your heater runs when you get home and turn it on as compared to how long it runs when you are home for 12 hours.

This same theory works for cooling your house in the summer.

Answer 2

In most cases, yes. The only caveat is if you have a heat pump. Heat pumps are generally not capable of rapid reheating without using a backup heat source. If that backup heat source is electric heat strips you could easily erase any savings from the "off" period.

Answer 3

I know there has been some talk about it taking more energy to bring a home back to a particular temperature than to maintain that temperature. Here's what I know. I live next to a home identical to mine. I have a programmablet thermostat that is set to 80 during the day and goes to 78 around 8pm. I'm home all day, she works and is involved in sports, so she is rarely home until late in the evening. I hear her a/c cycle on all day starting in the early morning and every hour or 2 all day and night. Even on days that it's over 100 my rarely goes on before 5pm it cycles on and off about as often as hers does during the evening. So, I don't see how it can be saving her more energy.

I say turn it off, open the windows when you come home if the air is cooler outside than inside and keep the drapes shut while you are away.  

Answer 4

I would actually suggest you turn the heater/ air conditioning unit OFF when you're not at home. That would save you a lot of money in the long run!