Cooling Degree Days (CDD) are relative measurements of outdoor air temperature used as an index for cooling energy requirements. Cooling degree days are the number of degrees that the daily average temperature rises above a given cooling balance point. The daily average temperature is the mean of the maximum and minimum temperatures in a 24-hour period. For example, supposing the cooling balance point for a meter was 62° F, mec would calculate 11 cooling degree days for a single day with a daily average temperature of 73° F.
Conversely, any day that the daily average temperature is equal to or below the cooling balance point, cooling degree days will be 0. If on another day the average daily temperature was 62° F or lower, cooling degree days for the same meter would be 0.
Using daily temperature data and the cooling balance point, mec adds up the cooling degree days for each day in a billing period to arrive at the CDD values associated with individual utility bills.