SEER stands for seasonal energy efficiency ratio. You can find this value on any modern central air conditioning system, while you can find an EER (energy efficiency ratio) on most window units. These two values differ slightly, but they both attempt to tell you how efficiently your air conditioning unit will cool your home.
SEER rating provides a more accurate estimate by taking seasonal temperature variations into account. Comparing the SEER rating of two air conditioners allows you to see how they stack up to each other but is it the most crucial factor when deciding between air conditioning units? How much should you rely on these ratings for your purchasing decision?
How to Compare SEER Ratings
SEER and EER are relatively straightforward values that tell you the ratio of cooling BTUs to watts of energy consumed. Calculating these values yourself can require a little math, but it's unnecessary if you're just trying to determine the efficiency of an air conditioning unit. The easiest option is to use an online energy savings calculator to see how two units stack up against each other.
It's also important to understand that SEER values are linear. In other words, doubling your SEER value will theoretically mean halving the energy costs of your air conditioner. You can use this fact to quickly gauge how much you'll save by purchasing a more efficient unit. While increasing your SEER rating by one point might not make much difference, a five-point increase can be significant.
Why SEER Isn't the Final Word on Efficiency
SEER provides a valuable back-of-the-envelope method to gauge the efficiency of an air conditioning system quickly, but it's not the only factor you should consider. Real-world efficiency can often be more challenging to gauge for two reasons:
- Ductwork and insulation losses
- Variable cooling needs
Old or poorly maintained ducts can often lose a substantial amount of conditioned air, ultimately reducing the efficiency of your AC system. Likewise, poorly insulated homes will realize lower real-world efficiency than ones with better insulation and a tighter building envelope. While you can still make a comparison with SEER values, you may not see the same gains from a more efficient system.
Varying cooling needs can be more difficult to understand. Since a typical single-stage system is either on or off, your AC will need to run at full power, even on cool days. Variable or multi-stage units help reduce these losses, but the higher SEER rating may not fully reflect the advantages. These efficiency differences may be more pronounced in unusually hot or cold summers.
While SEER is an excellent starting point for comparing AC units, it's not the only thing you need to consider. If you want to gain the most efficiency from your new AC system, make sure you also account for your home's ductwork and insulation and advanced AC features such as variable compressors. For more information on your AC unit, talk to an air conditioning service near you.