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Old 07-10-13, 08:37 AM   #9
AC_Hacker
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Quote:
Originally Posted by gasstingy View Post
Swapping 12 SEER AC for 19 SEER and being out of the 77% gas heat and into 10 HSPF electric heat, but I don't understand this number.
HSPF = Heating Seasonal Performance Factor. It is a way to rate a heat pump's performance with regard to heating efficiency. SEER is more about cooling, HSPF is more about heating.

HSPF is a number derived in a lab, assuming typical American climate (what is that?) and typical response of the heat pump to that climate. When the outside temperature is higher, air-source heat pumps are more efficient. When the outside temperature gets colder, air-source heat pumps become progressively less efficient. So, HSPF looks at the whole heating season and comes up with one average number.

In Europe, heat pumps are rated in COP (Coefficient Of Performance), which I think would be a better number to use. COP means the 'energy input' divided by the 'energy output'. For instance, a typical car has a COP of about 0.15 or 15%. Pretty low.

Your rig has a HSPF of 10, which can be converted to COP by dividing HSPF by 3.412

COP = HSPF/3.412 = 10/3.412 = 2.93 = 293% efficient.

That's pretty good.

If you want to compare how your heat pump compares to your old furnace, trot on over to Build It Solar, and check out their FUEL COMPARISON CALCULATOR.

This will let you put in your own local electricity and gas costs, the efficiency of your old furnace, and now that you know your COP (293%), you can also put in the efficiency of your heat pump.

You will be amazed.

Best,

-AC
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