If you’re shopping for a new air conditioning system this summer, you need to know how to judge their efficiency. Air conditioner efficiency is rated by their SEER number. That stands for the Seasonal Energy Efficiency Ratio, and it applies to air conditioners and air-source heat pumps.
The SEER is determined by dividing the amount of cooling output, measured in BTUs, by the total electric energy input, measured in watt-hours. Beginning in 2006 all residential central AC units sold in the US had to have SEER ratings of 13 or higher, 14 to qualify for Energy Star status.
The bottom line is savings. By upgrading from an older unit with a SEER rating of 9 to a new one with a rating of 13, you can save as much as 30% on your cooling costs.