Understanding SEER Rating

In the middle of the real estate boom, the United States Department of Energy mandated making the minimum SEER rating of our HVAC systems 13 SEER or greater . This would go in to effect in January of 2006, and many builders and HVAC companies were warehousing older 10 SEER units for cheaper installations and parts. I was a real estate agent at this time and the decision was not popular with many of my colleagues. “It’s just going to make homes more expensive” and “my old unit works just fine, why does the government have to get involved” were the most common complaints. We didn’t like it, but honestly I don’t think any of us could have explained what a SEER rating even meant!

SEER stands for Seasonal Energy Efficiency Rating and is an average of the unit’s cooling efficiency. Simply stated, the higher the SEER, the more the efficient the unit. As a mathematical formula it would read:

Total cooling output over the cooling season / total energy input over the cooling season

Luckily many of the older lower SEER units installed before 2006 are long gone. The average lifespan of an AC unit is 10-15 years, but it is possible that if you are still running one of the old ones it could have a SEER rating of about 6. It is not uncommon today to find units operating at a SEER as high as 27 and while the upfront cost is higher, you will pay less over the course of its lifetime.

Below is a comparison of the cost of operating a 6 SEER unit compared to a 13 SEER unit. Both are 3 ton units (36,000 BTU) running 8 hours per day. We’ll say that the cooling season is 4 months long and the average utility rate is .10 cents per kilowatt hour.

6 SEER

36,000 BTU/hr. x 976 hours / 6.0 SEER = 5,856,000 watts / 1,000 (to convert to KW) = 5,856 KW x $0.10 = $585.60 per year

13 SEER

36,000 BTU/hr. x 976 hours / 13.0 SEER = 2,702,769 watts / 1,000 (to convert to KW) = 2,703 KW x $0.10 = $270.30 per year

This is an annual savings of $315.00 per year, or $4725.00 over its average 15 year life span. Rebates from your local power companies will often bring the cost of the higher SEER units more in line with the minimum SEER models, so be sure to check before purchasing.

Even if you are not ready to replace your older unit, you might want to consider having your duct system tested. 20-40 percent duct leakage is not uncommon and a homeowner repair is not difficult. Doing this now will ensure that you are milking every last ounce of cool air from your existing system. It is likely you will begin to save money without replacing your existing system!