How much should I lower my heat to when I'm out?

Question

If too low, the system runs for hours to heat back to 68, which probably is less efficient. Anyone have an idea what the optimum point is? This is for a hot air system and outside temp is about 25-35 degrees.

Answer 1

In theory, if you shut your heat off completely and only had it turn back on enough in advance so you would be comfy when you got home, that would be most efficient. The heater is not less efficient if it has to run a long time to get it back up to temp.

But wide swings of temp are not that good for the furnishings and structure, which would be expanding and contracting quite a lot, and repeatedly.

The difference in temp between inside and outside, or the "Delta-T" changes the rate of heat flow from inside to outside. The greater the Delta-T, the greater the flow. So the lower the Delta-T, the less heat loss there is. If the temp inside was exactly the same as outside, there is no flow.

I've used some fairly extreme set-back temps with good results. 50F to 55F seems to work well, and it's just a matter of trial and error to adjust the timing to provide a "seamless" experience.
You might want to experiment with a digital thermometer that has a minimum and maximum temp memory. I've used a $10 digital barbeque thermometer to record what's going on while I'm out, to see how cold it gets relative to different outside temps and time away. Good question!

Answer 2

Normally, I would say to keep it at 68 degrees. But if your system runs for 'hours' to get back up to 68, then that doesn't sound right.

You can check and replace the filters yourself. Any other type of system checks, you may want to call a professional.

Answer 3

When I lived in WA. state, I kept my thermostat at 68 all year long

Answer 4

2 or 3 degrees saves more energy but it's really up to you

Answer 5

keep it at about 55 when you are not home if that is going to be out for 8 hrs plus