Efficiency Standards History: Minimum efficiency standards for split and single package central air conditioners and heat pumps are 13 SEER for central air conditioners, and 13 SEER and 7.7 HSPF for heat pumps, as of January 23rd, 2006.  Previous standards, which took effect on January 1st, 1992, for split and single package air conditioners were 10 SEER and 9.7 SEER, respectively. The standards for the heating side of split and single package heat pumps were 6.8 HSPF and 6.6 HSPF, respectively.

Product Description and Usage: Central air conditioners and heat pumps have become common household space-conditioning appliances in the United States. Residential systems are considered those with cooling capacities less than 65,000 Btu/h (19,000 watts). On a national basis, the saturation of households with central air conditioning (including heat pumps) has increased significantly.

Technology: Central air conditioners and heat pumps are appliances designed to provide cool and/or warm air to an enclosed space. Most models are manufactured as split systems, i.e., the outdoor unit is "split" from the indoor coil and connected to it via refrigerant tubing. The outdoor unit consists of a compressor, heat exchanger coil, fan, and fan motor. The indoor coil typically resides either on top of a furnace or inside a blower-coil unit and conditioned air is conveyed to the space to be conditioned (heated or cooled) via ducts. A flow control device (e.g., capillary tube, short tube orifice, thermostatic expansion valve) is located at the indoor coil. In "mini-split" systems, the indoor coil and flow control device are located in a self-contained unit that is hung on a wall inside the conditioned space. Conditioned air is conveyed without ducts. "Mini-splits" are not commonly found in the U.S. but are very popular in Japan and southeast Asia. Other models of central air conditioners are produced as single package systems. In package systems, all the components that comprise a split system, including the air circulation equipment, are placed in a single cabinet. The packaged system resides outdoors and conditioned air is conveyed to the conditioned space via ducts. There are other central air conditioner and heat pump types that are referred to as “space constrained” products, including small duct high velocity (SDHV) systems and through-the-wall (TTW) condensing units.

There are several technologies that could increase the efficiency of central air conditioners and heat pumps, including enhancements to the heat exchanger coils (e.g., enhanced fin surfaces and rifled or grooved refrigerant tubing), efficiency improvements to the compressor, and the use of two-speed or variable-speed blowers, fans, and compressors. The most energy-efficient central air conditioners and heat pumps on the market achieve efficiencies exceeding 18 SEER by utilizing variable-speed indoor blowers and outdoor fans coupled with two-speed compressors.

Efficiency Rating: Central air conditioners and the cooling portion of heat pumps are rated with a seasonal energy efficiency ratio (SEER). The heating portion of heat pumps is rated with a heating seasonal performance factor (HSPF). As their names imply, both the SEER and HSPF are efficiency descriptors that account for the equipment's performance over an entire cooling or heating season. The descriptors represent the ratio of the cooling or heating provided in a typical season (in Btus) over the energy input to the equipment (in watt-hours) during the same season.

The Air-Conditioning and Refrigeration Institute (ARI), the trade association representing most manufacturers of central air conditioners and heat pumps, provides both on-line and downloadable versions of directories of certified central air conditioning and heat pump equipment. These directories provide the cooling capacity and efficiency of all certified models.

Product Classes: For statutory purposes, residential central air conditioners and heat pumps are divided into several product classes that may be subject to different efficiency standards. For the new efficiency standards, DOE considered the following product classes:

• Split system air conditioners
• Split system heat pumps
• Single package air conditioners
• Single package heat pumps
• Through-the-wall condensing units, split system
• Through-the-wall condensing units, single package
• Small duct high velocity systems

Analyses: Under contract to DOE, LBNL's Energy Efficiency Standards Group (EES) conducted analysis for the ANOPR and the NOPR, including:

• Life-Cycle Cost and Payback Period Analysis
• Life-Cycle Cost Subgroups
• Shipments Analysis
• National Impact Analysis (National Energy Savings and Net Present Value)
• Utility Impact Analysis
• Environmental Assessment
• Employment Impact Analysis
• Regulatory Impact Analysis

EES staff examined the life-cycle costs to consumers of moving from 10 SEER to 11 - 13 SEER in a paper published by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) in 2002.