Quote:
Originally Posted by Daox
Excessive heater run times increasing bills is typically a myth (only exception is heat pumps that kick on resistance heater backup). Lowering the temp at night and while you're away will net you more savings. A cooler house = less heat loss. When your heaters are on, they are at 100% efficiency, so you don't even have cycling losses as some of the people with forced air have. Try setting it back when you're gone and I bet you'll see some decent savings.
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I think this is only partially true. If the house has a lot of thermal mass, I would guess that it is probably better to leave the temperature the same, or only fluctuate the thermostat <2 degrees. For example, my parents have a 1000 sq ft ICF home with a small 1.2 ton GSHP. They went out on vacation and wanted me to house sit. They had upped the temperature by about 4-5 degrees to around 78 F in summer (74 is comfortable to me). Since I ended up sleeping there, I had to knock it back down to a more comfortable level. It took about 3-4 hours for the house to cool down, with the GSHP running the whole time.
I may be completely wrong, but I just don't know if changing the thermostat applies to high thermal mass, tight homes. I would have to look at a complete system analysis to really know and understand.