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Let’s get through all of the jargon and try to get to the point as quickly as possible. All of these ratings are a calculation of how much energy you have to put into a system in order to get a BTU of heating or cooling out.


But the problem is that cooling and heat pump equipment has a bunch of variables that impact the numbers so they are all a little different.

Here is a quick summary

EER (energy efficiency ratio) = BTUh of output ÷ Watts of Energy Input 

The nice thing with EER is you can measure it real-time if you know the watts being used and the BTU’s being produced. No conversions needed, no fancy math. Measured EER is an easy snapshot but rated EER is another matter as it is only based on RATED conditions. It doesn’t take into account seasonal temperature or runtime variations.

COP (coefficient of performance) = BTUh output ÷ BTUh of Energy Input 

In other words COP is the same as EER but you convert the input to BTUh from watts by multiplying watts by 3.413. Also easy with one more bit of math added in. The same issue in that it is snapshot of performance or based on only one set of operating conditions.

SEER (Seasonal Energy Efficiency Ratio) = BTUh output ÷ Watts of Energy Input / Averaged over an entire cooling season 

So SEER is just like EER but theoretically would be the average EER if you measured it all through the cooling season and then averaged it. The PROBLEM is that isn’t the same everywhere… so it is still based on a set of conditions that are meant to replicate an average.

HSPF (Heating seasonal performance factor) = BTUh output ÷ Watts of Energy Input / Averaged over an entire heating season 

This makes HSPF exactly like the SEER but the winter (heating season) version where the EER is calculated and then averaged out. The same challenge exists in that not all places have the same set of operating conditions.

The solution lies in understanding each efficiency measure as well as the requirements of the particular market you work in to provide your customers with the best possible products to serve their needs. If you live in a market with very high outdoor temps like Phoenix you want to look at the extended performance data on the equipment you see and find systems that continue t perform well at high temperatures.

If you are installing a heat pump in Maine the same is true but reverse it.

Ratings are great… being situationally aware is greater.

— Bryan



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