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MN Renovator · 03-24-13, 07:48 AM

I think this is the correct math, let me know if I'm off-base.

1.08*40CFM*40 degree difference(70 inside 30 outside)=1728BTU/hr*24 hours=41,472BTU per day.
That's 8 hours of an electric 1500 watt space heater running or about $1.20 at 10 cents per kwh.
About .4 therms or $.40 if your total gas costs are a dollar per therm. So if your average outdoor temperature for a month is 30 degrees outdoors your rough number would be $12.40 if you are paying $1 per 100k BTU of natural gas or for electric resistance heating it would be about $37, about a third of that cost with a heat pump.

The bigger issue that I see is the moisture content that you might be dragging into the house in the summer if your dew point gets over 55 degrees.

03-24-13, 07:48 AM	#10
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	I think this is the correct math, let me know if I'm off-base. 1.0840CFM40 degree difference(70 inside 30 outside)=1728BTU/hr*24 hours=41,472BTU per day. That's 8 hours of an electric 1500 watt space heater running or about $1.20 at 10 cents per kwh. About .4 therms or $.40 if your total gas costs are a dollar per therm. So if your average outdoor temperature for a month is 30 degrees outdoors your rough number would be $12.40 if you are paying $1 per 100k BTU of natural gas or for electric resistance heating it would be about $37, about a third of that cost with a heat pump. The bigger issue that I see is the moisture content that you might be dragging into the house in the summer if your dew point gets over 55 degrees.