[Bldg-sim] Fundamentals: SEER/HSPF conversions

Kruis, Neal Neal.Kruis at nrel.gov
Tue Mar 8 12:01:01 PST 2011


The relationship between SEER and EER is going to vary from system to system and does not depend on the climate. Take a look at the AHRI certified product database:


They report both SEER and EER for all air conditioners and heat pumps that have been tested. There is no way to convert directly between SEER and EER (or HSPF and COP) without having the results from the all of the AHRI tests which are usually kept confidential. The approximation of 0.875 accounts for part load cycling losses, but also how the system performs at other test conditions. It is probably a fair assumption, though you might want to check out the Building America House Simulation Protocol which uses:

EER = -0.02*SEER^2 + 1.12*SEER

This is based on a thesis written by a student at University of Colorado. The same thesis used:

COP_47 = -0.026*HSPF^2 + 0.624*HSPF

Here is the reference for the thesis:

Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations. Masters Thesis, University of Colorado at Boulder.

Hope this helps,

Neal Kruis
Electricity, Resources & Building Systems Integration
National Renewable Energy Laboratory
1617 Cole Blvd. MS 5202
Golden, CO 80401
(303) 384-7384

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Tuesday, March 08, 2011 12:36 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Fundamentals: SEER/HSPF conversions

I understand HSPF is fundamentally the same thing as SEER, only it's representing a heating season instead of a cooling season.

When handling SEER, I used the following equation to come up with a seasonally averaged cooling EER:

EER = SEER * 0.875

My limited understanding is that 0.875 is a conceptually a constant representing a "part load cycling factor" of sorts for a typical cooling season.  I've read multiple times this constant should vary with climate (commonly, "Georgia = 0.8" and "California = 0.9").  While that makes sense to me, I've yet to see a citable climate map or similar reference breaking down what factor to use where... so up to this point I've stuck with 0.875 for simplicity's sake.

My root question is:  Is there a comparable "part load cycling factor," for one or more climates, for converting HSPF to a seasonally averaged heating COP/EER?

Put another way:  EER = HSPF * ???

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Smith & Boucher Engineers
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