# Thread: Calculating kwh of furnace fan

1. Regular Guest
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Is there any way for a homeowner to figgure out what the electrical usage of the blower on a furnace is? Are you better off running the fan continuously in the winter? Should I use the "Intermitten Fan" setting on my thermostat? This is on a new single stage furnace.

Thanks!

2. Professional Member*
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amp draw on the motor multiplied by 120 (volts)= kilowatts.
multiply Kilowatts by whatever your electrical rate per kilowatt is.

3. Professional Member
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Originally posted by Black Adder
amp draw on the motor multiplied by 120 (volts)= watts.
divide watts by 1000 for kilowatts.

multiply Kilowatts by whatever your electrical rate per kilowatt is.
FIXT

4. Grumpy Old Man
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Yep...

A (amps) x V (volts) = W (watts) / 1000 = KW (kilowatts)

Then take your KW cost x the above figure. This will provide you with an hourly cost.

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my ex complained of "cold" air blowing when burner was off --
I tried to run fan all time when living up north to keep air stirred

amp draw = actual reading for greatest accuracy --

probably not worth figuring -- 0.745 watts = 1hp. fan motor is probably 0.3hp -- so at \$0.1/kwh, you will spend a dime ea 3 hr.

but, then you would need to clock how long the blower runs in "auto" mode & subtract that value to get the added cost.

6. Originally posted by jultzya
Yep...

A (amps) x V (volts) = W (watts) / 1000 = KW (kilowatts)

Then take your KW cost x the above figure. This will provide you with an hourly cost.
Are you suggesting a HO take an amp draw on his blower.

BTW, thats KWH, not KW.

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I have a home owner want to put glass windows to his porch hi like to run supplied grills to it from the main trunk ? can i do it do i have to run a return back to the furnace, or what will be a better idea .

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I seem to recall that static pressure makes a difference on how much power is used with a PSC motor. Paradoxically the higher the static the less power is used but the less air is moved. Is that correct?

9. during the winter months, when its cold, the furnace will be runnning pretty regularly unless its drasticly oversized. (in which there is no fix). I dont see running the fan constently as being any benifit unless you are using some sort of high end filtering system or are overcoming a poor distribution system (ducts).

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Some of the replies were to multiply the nameplate amps for the motor by 120 to get watts. Ok in a pinch but will tend to overestimate the cost - a motor won't always draw its nameplate amps. A PSC motor on one of its lower speed taps will draw somewhat less. An ECM motor can draw a lot less.

11. Grumpy Old Man
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Originally posted by beenthere
Are you suggesting a HO take an amp draw on his blower.
Nope, just giving him the formula to be able to figure out the operating cost. He can either use the furnace info (for an estimated cost) or get the actual amperage from the tech when the next PM is done.

12. Took ya all day to think of that answer huh. LOL...

13. Originally posted by redcell
Are you better off running the fan continuously in the winter?

only if blower goes to a very low speed when calling for fan only. blower running at normal cooling speed when burners are off makes for a very cool draft.

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