# Heat Pump Efficiency for use with Fuel Comparison Calculator

To use the Fuel Comparison Calculator for heat pumps, you need to find out the seasonal COP (Coefficient Of Performance) for the heat pump, and multiply this by 100 to get the effective efficiency to fill into the Efficiency column.

For example, if you find that the heat pump of interest to you has a seasonal COP of 2.2 when installed in your climate, then the effective efficiency is (2.2)(100) = 220   -- you would enter 220 in the "Efficiency" column.

The actual heat pump COPs for both air and ground source heat pumps depends on a number of factors.   Heat pumps do not perform in cold climates as well as they do in not so cold climates.  If it gets cold enough, heat pumps revert to simple resistance heaters with an efficiency of around 95%.

What you are looking for is the average COP for the full heating season for the heat pump installed in your climate.  This will likely be well below the COP when the heat pump is operated under more favorable conditions, but it is important to get an average seasonal COP.

Some sources provide an HSPF -- to convert this to a COP, divide the HSPF by 3.412.  For example an HSPF of 6.8 equates to a seasonal COP of (6.8 / 3.412) = 1.99.

One estimate from a seemingly reputable source says that new air source heat pump seasonal (i.e. for the whole heating season) have average COPs that range from 1.6 to 2.8, and new ground source heat pump seasonal COPs range from 2.4 to 3.5.  The link to the related article is listed below.   There are a few studies out in which the actual performance of heat pumps installed in real homes was measured -- these would be worth looking for if you are thinking of a heat pump.

From the emails I get and material I see, ground source heat pump performance depends a lot on good design and good installation.  It appears to me that there are a significant number of GSHP installations that don't meet customer expectations due to poor design or poor installation -- so make sure you do your homework and get a good contractor.

Article comparing heating systems and including some discussion of heat pumps.

Comments/letters in response to above article:

An Information Survival Kit for the Prospective Geothermal Heat Pump Owner, Rafferty for the DOE...

Good information on the different styles of GSHPs and the most frequent questions.

To convert the HSPF to a COP divide by 3.412  -- e.g. an HSPF of 8.2 would equate to seasonal COP of 2.4, or an effective efficiency of 240%.

Some material on seasonal COPs

A monitoring of actual homes in Florida for actual COPs achieved.

Gary April 28, 2008, May 2, 2008