Central air conditioners and heat pumps use a vapor compression cycle to provide cooling or heating. The most common type of system, split systems, consists of an outdoor condensing unit and an indoor evaporator unit which are connected by a refrigerant line set or loop. As the refrigerant enters the indoor unit, its pressure drops causing it to evaporate and cool. A blower moves indoor air across the evaporator coil and then into a duct system for circulation through a building. Central air conditioners are most typically installed with a gas furnace. A heat pump is a central air conditioner that can be operated in reverse to heat indoor spaces during cold weather.
New standards for central air conditioners and heat pumps took effect in 2015. These standards, developed jointly by air conditioner manufacturers and efficiency proponents and adopted in a DOE regulation published in 2011, provide for the first-ever regional standards. The standards provide for a minimum cooling efficiency requirement of Seasonal Energy Efficiency Ratio (SEER) 14 for split system central air conditioners in the South and the Southwest. For the North, the standard remains SEER 13 (the level that took effect for the nation as a whole in 2006). In the Southwest (a region comprised of Arizona, California, Nevada and New Mexico), air conditioners must also meet an Energy Efficiency Ratio (EER) requirement which helps ensure efficient operation at high outdoor temperatures. For heat pumps, the standard is the same in all regions: SEER 14 and heating season performance factor (HSPF) of 8.2.
In 2015, DOE convened a negotiated rulemaking process to recommend the next revision to the central air conditioners and heat pump standards. The negotiation process succeeded and DOE published a direct final rule containing new standards in January 2017. The newly negotiated standard will take effect in 2023. As part of the negotiation process, the test method for air conditioners was updated and improved, which will cause an adjustment to air conditioners and heat pumps ratings, making the 2023 standard not directly comparable to the current standards. DOE estimates that the newly negotiated standards will save consumers about $12.2 billion from products sold over a thirty year period.
About 65% of existing U.S. homes have a central air conditioner and about 17% have a heat pump. However, with the exception of the coldest climates, virtually all new homes are built with a central air conditioner or heat pump. Compared to older units, products meeting the latest standards generally incorporate improved compressors, expansion valves and better and larger heat exchangers. Current standards can be met with single speed compressor technology, while advanced, variable speed products enable SEER performance far higher than the minimum standards and can also improve comfort by providing more even heating or cooling.