An air conditioner's SEER rating refers to the ratio between the amount of cooling it can produce and the amount of electricity it consumes in terms of wattage. A higher SEER rating indicates that an air conditioner has a greater energy efficiency.
Air conditioners produced and sold in the United States after 2005 must have a minimum SEER rating value of 13. As of 2015, this regulation does not include window-mounted units, which typically still have a SEER rating of 10. An air conditioner with a higher SEER rating reduces overall power consumption, with the difference between a SEER 13 and a SEER 9 unit saving up to $300 in annual utility costs.