HSPF is an acronym for Heating Seasonal Performance Factor. To understand what is means we first must understand an older term we used many years ago. This term, EER, simply stood for Energy Efficiency Ratio.
EER is a very simple ratio of BTU divided by Watts. Watts are the smallest
measurement of the electricity we buy. Most of our customers buy 1000 watts or 1
Kilowatt for about 10 cents.
Basically it a way of stating WHAT YOU GET for WHAT YOU PAY. Instead of
saying that your car gets 8 Miles Per Gallon you could say that it has an Energy
Efficiency Ratio of 8. If you could buy a car that would do everything that your old car
does but would get 16 MPG, you would only spend half as much money on gas.
So how does it vary from EER or COP? It is Seasonally adjusted. Just like your car
gets different MPG in different situations, so Heat Pumps get different EERs at different times. HSPF is AHRI Air conditioning, Heating, and Refrigeration Institue's best estimate of a particular systems Seasonal average EER.
Most importantly, a higher HSPF rating is better, and it is proportional. A system with a 50% higher HSPF will use 50% less electricity.
Weber Refrigeration Heating and Air Conditioning