In by Mark Goodman

A measure of the energy efficiency of equipment over the cooling season, representing the total cooling of a central air conditioner or heat pump (in BTUs) during the normal cooling season, as compared to the total electrical energy input (in watt-hours) consumed during the same period. SEER is based on tests performed in accordance with AHRI 210/240 (AHRI 2003).

Merriam-Webster Online Dictionary
seer (noun)
one that sees
a) one that predicts events or developments
b) a person credited with extraordinary moral and spiritual insight
one that practices divination especially by concentrating on a glass or crystal globe
SEER (Wikipedia)

The efficiency of air conditioners is often rated by the seasonal energy efficiency Ratio (SEER) which is defined by the Air Conditioning, Heating, and Refrigeration Institute in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment. A similar standard is the European seasonal energy efficiency ratio (ESEER).

The SEER rating of a unit is the cooling output during a typical cooling-season divided by the total electric energy input during the same period. The higher the unit's SEER rating the more energy efficient it is. In the U.S., the SEER is the ratio of cooling in British thermal unit (BTU) to the energy consumed in watt-hours. The coefficient of performance (COP), a more universal unit-less measure of efficiency, is discussed in the following section.

For example, consider a 5,000-British-thermal-unit-per-hour (1,500 W) air-conditioning unit, with a SEER of 10 BTU/W·h, operating for a total of 1000 hours during an annual cooling season (e.g., 8 hours per day for 125 days).

The annual total cooling output would be:

5000 BTU/h × 8 h/day × 125 days/year = 5,000,000 BTU/year

With a SEER of 10 BTU/W·h, the annual electrical energy usage would be about:

5,000,000 BTU/year / 10 BTU/(W·h) = 500,000 W·h/year

The average power usage may also be calculated more simply by:

Average power = (BTU/h) / (SEER) = 5000 / 10 = 500 W

If your electricity cost is 20¢/kW·h, then your cost per operating hour is:

0.5 kW * 20¢/kW·h = 10¢/h
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