Room air conditioners are encased AC units designed primarily for mounting in a window or through a wall. They are constructed to deliver conditioned air into a room without the use of ducts or with very short ducts. Room AC units have their own source of refrigerant and dehumidification as well as a mechanism for circulating or filtering the air, and may also include mechanisms for ventilation and heating.
Room air conditioners were regulated by several states in the 1970s and 1980s and became federally regulated in 1987. The standards vary as a function of cooling capacity and other features, but for the most common type of unit (an 8,000–13,999 Btu/hour unit with side-vents) the 1987 law required an efficiency of 9.0 EER (energy efficiency ratio), effective 1990. EER is cooling capacity (in Btu/hour) divided by power input (in watts). In 1997, DOE published amended standards for room air conditioners, which became effective October 2000. For the most common unit, the EER must be at least 9.8.
In July 2010, efficiency proponents and manufacturers agreed to jointly support new room AC standards that would reduce energy consumption by about 11% for the most common units. DOE published a direct final rule on April 21, 2011 that reflects the standard levels in the consensus agreement, and on August 24, 2011, DOE confirmed adoption of these standards. The standards are based on a new metric, combined energy efficiency ratio (CEER), which incorporates standby energy consumption, and the standard for the most common unit is 10.9 CEER. DOE estimates that the new standards will save 0.31 quadrillion Btus (quads) over 30 years and yield a net present value of $1.5 billion at a 3% discount rate. The new standards took effect June 1, 2014.
About 6 million room AC units are sold in the United States each year; 26% of all households have at least one room AC unit (around 50% of these households have two or more); and approximately 20% of all room AC units are over 10 years old. Technology options for improving room air conditioner efficiency include efficiency improvements in compressors, fans, fan motors, and heat exchanger improvements such as increased fin density and improved fin and tube design.