Degree Day

A unit used in meteorology and engineering to measure the demand for heating or cooling.

In the United States the agreed critical outside temperature is 65°F (18.3°C). Below this tempeature heating is needed and above it cooling is needed.

The number of degree days recorded on a given date is equal to the difference between 65°F and the mean temperature for that date (the average of the highest and lowest temperatures for the day).

The total number of heating and cooling degree days recorded in any period of time is proportional to the demand during that time for energy used in heating and/or cooling buildings.

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Subjects: Heating Ventilation and Air Conditioning