Room air conditioners (or window ACs) are designed to cool individual rooms and are mounted in a window or through a wall.
DOE finalized the current standards for room ACs in 2011, and they took effect in 2014. The standards, which were based on a consensus agreement between manufacturers and efficiency advocates, require minimum combined energy efficiency ratio (CEER) values that vary based on cooling capacity. CEER is expressed as the ratio of the cooling capacity (Btu/h) to the power input (W). For typical room ACs with cooling capacities less than 8,000 Btu/h, the minimum CEER is 11.0. Relative to the previous standards, which were in effect from 2001 to 2014, the current standards represent energy savings of about 11%.
About one-quarter of all US households have at least one room AC unit, and about half of these households have two or more. Technology options for improving the efficiency of room ACs include more efficient compressors, fans, and fan motors, and improved heat exchangers.