The efficiency with which central air conditioners and heat pumps produce cooling is most commonly rated according to their SEER, or Seasonal Energy Efficiency Rating. The higher the SEER, the higher the efficiency.
This article covers a number of issues related to the SEER:
The United States has set minimum values for the SEER of central air conditioners and heat pumps. Beginning Jan. 1, 2016 central air conditioners sold in the United States are required to have the following minimum SEER:
- In Northern states the minimum SEER remains at 13. (Northern states include: Alaska, Colorado, Connecticut, Idaho, Illinois, Indiana, Iowa, Kansas, Maine, Massachusetts, Michigan, Minnesota, Missouri, Montana, New Hampshire, New Jersey, New York, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, Utah, Vermont, Washington, West Virginia, Wisconsin and Wyoming)
- In Southeastern states, the minimum SEER is 14. (Southeastern states include: Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia)
- In Southwestern states, the minimum SEER is 14 and the minimum EER is 12.2. (Southwestern states include: Arizona, California, Nevada, and New Mexico)
These requirements were new as of 2015 (as was the regional variation in the minimum SEER). In previous years:
- From Jan. 1, 2006 – Dec. 31 2014, all central air conditioners sold in the United States were required to have a minimum SEER of 13.
- From Jan. 1, 1992 – Dec 31, 2005, all central air conditioners sold in the USA were required to have a minimum SEER of 10.
- It is often estimated that before 1979, the SEER of new air conditioners ranged from around 4.5 to 8.
These minimum SEER values only affect new units sold in the United States. For example, air conditioners with a SEER of less than 13 that were manufactured before January 2006 may still be sold and installed. The standard does not require that homeowners swap out existing inefficient units for more efficient models.
As of Spring of 2017, the most efficient air conditioners have a SEER of 33.
Heat pumps have a minimum SEER of 14 across the United States beginning in 2015.
The Energy Efficiency Rating (EER) of a particular cooling unit is the ratio of output cooling energy to input electrical energy at a given operating point. The Air-Conditioning and Refrigeration Institute standardized this rating, which reports central air conditioning efficiency at a 95 degree F outside temperature and an 80 degree F inside temperature.
EER is measured at one set of conditions, while SEER is a seasonal average, measured over a range of conditions. Since air conditioning units don’t perform comparably at all temperatures, there will be differences between the single condition EER testing uses, and the range of weather conditions SEER testing uses. SEER measures the expected overall performance for a typical year’s weather in a specific location. By contrast, EER measures the unit’s efficiency at peak output.
For areas of the country where it is 95 degrees F or higher most of the time the air conditioner is on, the EER is usually more accurate. More moderate climates use SEER, which provides an average, taking into account highs and lows of a home’s cooling pattern. The important thing is to compare one air conditioner’s EER to another’s EER, or SEER to SEER. Comparing the EER of one model to the SEER of another model will not be accurate.
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Upgrading from a less efficient central air conditioner to a more efficient central air conditioner (assuming that everything else is the same) will save you money. The following chart shows the expected savings over 5 years due to improved efficiency based on national average usage data and purchasing electricity at US $.11 / kWh.
For example, if you were choosing to upgrade from a 10 SEER air conditioner to either a 14 SEER or an 18 SEER air conditioner you might expect to save $465 in the upgrade from 10 to 14 SEER, or $720 if you upgraded to an 18 SEER unit. You could then compare the extra $255 in expected savings to the additional cost of the higher efficiency unit to determine if your payoff period would occur within the first 5 years.