Limitations of SEER for measuring efficiency

Conventional wisdom assumes that a 30% increase in the seasonal energy efficiency ratio (SEER) of a unitary air conditioner or heat pump will result in a 30% decrease in energy consumption. More exactly, a 30% increase in SEER will result in a 30% increase in efficiency when the outdoor temperature is 82degreesF (27.8degreesC) and the indoor temperature is 80degreesF (26.7degreesC) - the specified rating conditions. Prediction of the actual energy or demand savings of modern cooling and heating equipment with a single indicator can be "seriously inaccurate."(1) As an example, the performance data of an 18-SEER product line is compared to a 10-SEER product line from the same manufacturer.