The number of Cooling Degree Days (CDDs) during a period is an index that is intended to relate to the amount of cooling used during that period. Because cooling is most often used during summer, CDDs are most often calculated over some or all of the summer period, and are designed to reflect how hot that period is. The number of CDDs on one day is defined to be the number of degrees by which the Average Temperature on that day exceeds a threshold, usually taken to be 65F. The number of CDDs over a period is just the sum of the number of CDDs on each day during that period. For instance, a single day of 70F corresponds to 5CDDs. Two days of 70F correpond to 10 CDDs and so on. Days during which the Average Temperature is less than 65F do not contribute any CDDs. This somewhat complicated formula is an attempt to create a linear relationship between a meteorological index and the consumption of power. Contrast with Heating Degree Days (HDDs).
An indicator of space cooling demand. The cooling degree days for a single day equal the average of the highest hourly temperature and the lowest hourly temperature for the day minus 65 degrees Fahrenheit, if greater than or equal to zero.
Cooling Degree Day (CDD) is a form of degree day used to estimate energy requirements for space cooling (e.g., air conditioning, refrigeration). One cooling degree day is obtained for each degree that the daily average temperature is above the base of 65 degrees F. For example, if the daily high temperature is 84 degrees and the daily low is 60 degrees, the average temperature for that day is 72 degrees F. The daily CDD is 7. If the average temperature is less than or equal to 65 degrees, the daily CDD is zero.