I have a ClimateMaster 3 ton closed loop system. My house is 60 yrs old and has new windows, doors, etc. but not the best insulation. It does a good job heating and cooling. I was wondering: does it make sense to set the thermostat (heating) back 2 degrees at night? It's set at 68F in the day and currently 66F at night. In the morning it runs a long time to get it up to 68F, and I'm wondering if I should just leave it at 68F all the time. Are there definitive studies that address this? Thanks.

I leave mine set at 68* and don't set back.

Just be sure the aux heat is not coming on during the raising of temp

I don't know if there are definitive studies.

ChrisJ

In cases where the heating system runs at a fixed efficiency, setback always saves money. But aux heat is far less efficient and variable output heat pumps switch to a somewhat lower efficiency. So you probably don't want to do it.

What you find most comfortable is up to you.

We tell people to set it and forget it. Unless it is a comfort desire for you to lower the temp at night, it is the most economical way to run it. I recall a study where 2 nd stage operation was actually more efficient, presumably due to high pumping power, but that is not the norm with efficiently designed systems. What kind of CM heat pump do you have?

We have a Climate Master TEV038, closed loop. Had if for almost 2 yrs and like it very much. We used about $170 more electricity last year than our neighbors with similar houses (according to the elect. company data) but NO OIL! That saved almost $3,000 (including service and oil delivery plan). Thanks for your help.

It is a 3 ton dual stage. Chances are that you have higher comfort when keeping it at constant temp. Plus when temps are getting colder you might have an even harder time catching up to 68F. Try it out. You know how it is now as a comparison. Let us know.

Yes, you are correct about the "catching up." I have it set to bring the temp up to 68F starting at 7 A.M. and it takes until 10 or 11 A.M. to do that. It's usually running in first stage by the end, however it is often in 2nd stage most of the morning. The AUX doesn't come on too often unless it's really cold (as it was last winter). The electric bills we get for the months of Jan/Feb are usually around $250-300, but then it drops after that. I have a neighbor with a similar CM system and he just leaves it at 70F all the time. Not sure what his electric bill is though. I'm still learning about these systems so any help you can provide would be appreciated.

Again, leave it to 68F and see what happens. You can close the damper in your bedroom a bit if you like it colder there. You want to avoid having the aux on.

There is NO POINT in setting back a thermostat even a fixed efficiency system. If you dont' believe me try this(for heating contractors)
Run a load calc with your outdoor design condition and indoor conditions at 70. Now rerun the load calc with a standard setback(say 5 degrees for a gas furnace) now run both through an energy analyer and see the difference in costs for each load calc. For my area and my gas/electric rates it was around a $90 per year savings on a house with a 36K heat less at design outdoor temp and 70 degree indoor temp vs design outdoor temp and 65 degree indoor temp. Now factor in that probably less than half of the day is at setback so now we are only saving $45 per year and then factor in that at somepoint you have to heat the house back up too, so thats probably cutting the savings in half again, so now we are at a savings of $22.50 per year in Portland Oregon with a 5 degree setback on a 95% furnace and 13 SEER AC system