Guidance on Thermostat Settings

Old 01-02-02, 08:12 AM
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Guidance on Thermostat Settings

Greetings -
I'm hoping someone could help me solve the following problem: Is it more cost effective to turn the thermostat essentially off every night and heat back up in the morning, or, to just lower the temp at night? My dear wife, who is blessed with the fabled "woman's intuition" thinks it is perfectly obvious that turning the t-stat way down at night (like to 45 or lower) and then heating back up in the morning is way more cost effective than turning it down (say to 55 or so) since a mere lower setting would require the furnace to turn on and off a few times during the night.
I know there are alot of variables here, like house insulation, outside temp, length of time furnace is off at night, etc. Basically she wants house to reach equilibrium at about 60 during the day and let it fall as low as it can at night; I'd prefer to just lower the temp at night to about 55 or so. (The issue of comfort is another story here. I'm just asking about the economics). Somehow I think it may not be a linear situation in that it could well take sufficiently more energy to re-heat a really thoroughly cold house than to maintain it at a lower temp. Perhaps someone would have an opinion on this issue or could point me to some relevant studies.
Old 01-02-02, 12:56 PM
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I'm not an HVAC technician or energy expert by any means, but I've always read and heard that it is best to set a tstat at a certain low temp, and leave it alone.
It supposedly costs more to heat up from a lower temp, than to maintain a steady low temp.
You might check for information from your power or gas utility company. Most of them have a lot of free info about energy conservation and heating & cooling.
Good luck!
Old 01-02-02, 04:08 PM
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You've asked a valid question thats as old as the hills. Ask a dozen people and you'll probably get a dozen different answers.A little logic goes a long way and I don't by any means want to start an internal war. My answeer is this: traveling on the open highway in your car, you will get more MPG by using the speed control by maintaining a constant speed. The same holds true for heating or cooling your house. Set it and forget it. But for our comforts sake, most of us like to drop it down a little at nitetime. Drop too low and you then have to play catchup. Thats my opinion on economics.
Old 01-02-02, 04:36 PM
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I am an HVAC tech. It is cheaper and more comfortable to set the night time heating temperature 10 to 12 deg. F. lower at bed time, better yet invest in a good programmable thermostat. You are dealing with more than a linear flow here, you need to take into consideration the heat loss or gain of your home, your life style and the thermal mass of your home and furnishings. In the summer time here in Oregon I suggest to my customers that they set the day time occupied and evening setback cooling temperature the same usualy around 74 deg. F. and heat setback in winter of 10 to 12 deg. F. What good is a comfort system if you are not comfortable? Ron P. American Engineering Inc.

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