SEER Ratings Explained

SEER Ratings Guide

SEER stands for Seasonal Energy Efficiency Ratio and was defined by the Air Conditioning, Heating, and Refrigeration Institute. The SEER rating of a unit is the cooling output of the system during a typical cooling season divided by the total electric energy used in that same period. In the United States, we measure cooling by British thermal units or BTUs.
So you may be asking why you need to know about SEER ratings. The biggest thing that a homeowner needs to take away from this is that the higher the SEER rating, the more efficient the unit is. Let's compare a 13 SEER and 16 SEER 2 ton air conditioning units. By dividing the BTUs per hour by the SEER rating, we can get the watts per hour used by each unit. So: 13 SEER: 24,000 BTUs per hour / 13 = 1,846 watts per hour 16 SEER: 24,000 BTUs per hour / 16 = 1,500 watts per hour
Now that we have our watts per hour, we can calculate our costs per hour by multiplying our watts per hour by our electricity cost. Let's assume that our electricity costs 20 cents per kilowatt hour. 13 SEER: 1.846 kw x 20 cents per kw = 36.92 cents per hour 16 SEER: 1.500 kw x 20 cents per kw = 30 cents per hour
We now have the operating cost per hour, but let us compare the yearly usage savings between the two units. Let's assume that the air conditioner will run 4 hours a day for 125 days a year. We can then figure out that the unit will run for 500 hours a year and can then multiply that by the cost per hour to operate the unit. 4 hours a day x 125 days a year = 500 hours 13 SEER: 500 hours x 36.92 cents per hour = $184.60 per year 16 SEER: 500 hours x 30 cents per hour = $150.00 per year
So in this scenario, the 16 SEER unit would save the homeowner roughly $34.60 a year on the electric bill. That might not sound like much, but when you factor in the savings for 15 years, that $34.60 per year ends turns into $519 of savings and would cover the increased price of the more efficient system.

SEER Rating Frequently Asked Questions

What is a good SEER rating for an air conditioner?
In general, a higher SEER rating correlates to higher energy efficiency. Today's HVAC and AC units carry a minimum rating of 13 in the northern U.S. and 14 in the southern U.S. (the U.S. Department of Energy enforces this at the regional level)⁽¹⁾, but this number can exceed 20 in some of the most capable units. One thing to keep in mind when understanding SEER ratings is that there is a significant amount of variability involved based on your installation, usage and environment.
What is considered a good SEER rating will depend on where you live and what your cooling needs are. For homes in hot climates like the southern U.S., although you can use a 14, we often see a good SEER rating between 16 - 21. In the cooler climates like the northern U.S., a good SEER rating starts at 13 and often going to 16 - 18 is enough, but can go all the way up to 21, as well. Keep in mind that SEER ratings are based on optimal conditions, so your system's efficiency may be not as good as the rating depending on a variety of factors.
Is a higher SEER rating worth it?
When compared to older units, newer models will generally provide an appreciable SEER-rating upgrade. For example, you can expect a SEER rating in the single digits from some older A/C units, so upgrading to a newer one should provide a higher operational SEER rating (or ratio). Over a long enough time horizon, this kind of upgrade will pay off - it's only a matter of figuring out how long until you recoup your investment. And tax credits and manufacturers' rebates are also often available to further boost your savings.
How much more efficient is a 16 SEER vs. 14 SEER?
SEER stands for Seasonal Energy Efficiency Ratio and the higher the rating, the more efficient a system is. Assuming units are similarly sized, we can do some simple calculations to figure out the difference in energy efficiency between a 16 SEER and a 14 SEER unit.
Consider two units of similar size. 14 SEER: 24,000 BTUs per hour / 14 = 1,714 watts per hour; 16 SEER: 24,000 BTUs per hour / 16 = 1,500 watts per hour. The 16 SEER unit would use 214 fewer watts of electricity per hour than the 14 SEER unit.
Assuming an energy cost of 20 cents per kw, we can calculate how much it costs to run each unit per hour. 14 SEER: 1.714 kw x 20 cents per kw = 34.28 cents per hour 16 SEER: 1.500 kw x 20 cents per kw = 30 cents per hour The 16 SEER unit is costs 4.28 cents less per hour to operate than the 14 SEER unit.
Four hours a day x 125 days a year = 500 hours 14 SEER: 500 hours x 34.28 cents per hour = $171.40 per year 16 SEER: 500 hours x 30 cents per hour = $150.00 per year The 16 SEER unit will save approximately $21.40 per year in energy costs.
While the higher rating is going to function more efficiently, this is only in truly ideal and identical environments. If you're most concerned about the financial component of it, you'll need to weigh all costs and operational considerations. If you strictly are choosing between the more efficient of the two systems, then the higher rating is a reliable indicator of energy efficiency.
(1)Department of Energy. CAC Brochure. Informational Brochure. PDF. Accessed 16 July 2020. https://www.energy.gov/sites/prod/files/2015/11/f27/CAC%20Brochure.pdf