SEER is an acronym that stands for seasonal energy efficiency ratio. A SEER rating is a description of how much cooling power an air conditioner produces relative to the electricity that it consumes. In a SEER rating calculation, the cooling power is measured in British thermal units (Btu) and the electricity consumption is measured in watt hours. The higher an air conditioner's SEER rating, the more efficiently it runs.
Determine the number of watts per hour (Wh) that the air conditioner uses during the cooling season. This is a measurement of the amount of electricity that the air conditioner consumes, and can be found in the device's manual.
Determine the number of British thermal units (Btu) that the air conditioner generates during the same period. This is a measurement of the amount of cooling energy the air conditioner produces, and can also be found in the device's manual.
Divide the Btu's by the Wh. The result of this division is the air conditioner's SEER rating. For example, if your air conditioner generated 100 Btu's and consumed 10 Wh, you would divide 100 by 10 to get a SEER rating of 10.
The general formula for determining SEER ratings is: SEER = (Btu's of cooling output over the cooling season) / (Watt hours of electrical input over the cooling season).