Electric Furnace economy questions

Old 10-24-12, 09:48 AM
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Question Electric Furnace economy questions

I have two questions which I would like some input on, regarding electric furnace economy. Firstly a bit of background :
Furnace is just 4 yrs old, two stage with a top output of 17Kw. Front of house is South facing and benefits ( especially on sunny winter days ) from solar gain through the front windows - this can raise the temperature into the 70's during the day. Now here are the questions :

1. Does it cost more / is less efficient, to run the furnace on low for a longer period of time to raise the temp from 62 to say 68 degrees ( giving a more even heat ) than to run it on high for a shorter time ( I believe the low output is about half that of the high ) or will it be about the same ( bar the cost of the fan running longer on the low setting ) ?

2. As stated above, I can get the temp up during the day with the sunshine through the windows. Now, let's say its 72 degrees by sunset, will it cost more to have the furnace maintain that 72 degrees for the rest of the evening than it would to let the house cool down to say 68 and then maintain that 68 degree temp? ( ie. if the starting temp is 68 degrees, does it cost the same to maintain that 68 degrees as it would to maintain 72 degrees, if the starting temp was 72 degrees?)

I hope those questions make sense! I look forward to your input on this! Thanks.
Old 10-24-12, 10:03 AM
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Although I'm no furnace expert...I know electricity pretty well.

1. It makes no difference power wise. 1/2 power for twice as long....or full power for 1/2 as long...all same. Except for the fan...as you noted.

2. Yes...maintaining a higher temp will cost more than a lower one. It doesn't matter what the start temp is....except of course if it's higher...it will take a while to drop down to your set temp...saving energy. If it's lower than your set temp...you will have to bring it up initially...using more energy.
Old 10-24-12, 10:42 AM
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Thanks Gunguy 45

Thanks for you quick reply. I know that there are a lot of factors involved when you get into the finer details of what is more / less economic, but it was to get a general idea if there was a difference in how you use the furnace, as to wheather it would cost more / less to run. I guess in the long run, an apple is an apple, and thats it!
Thanks again!
Old 10-24-12, 11:37 AM
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Here's how setback/programmable thermostats save you money: The cost of bringing the house back up to the higher temperature is pretty much a wash with the money you save while it drops. The savings is incurred during the time when the house is maintained at the lower temperature. Long answer for your question about whether to let the temperature drop at night.
Old 10-24-12, 04:00 PM
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Heat loss is proportional to the temp difference between outside and inside.

With a programmable stat, you start saving money as soon as the temperature starts dropping below the normal setting. Savings are greatest once the indoor temp drops down to the setback temperature setting.

Turning down the heat at night/during the day may save 10% at most; in some cases it's possible to save more than that by air sealing and upgrading insulation if practical and cost effective. (every house is different in that regard)

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