dd Heating Degree-days is a unit of measure for calculating the effect of temperature on the consumption of energy (e.g. heating oil) to heat a location, essentially the opposite of Cooling Degree-days.
A unit measuring the extent to which the outdoor mean daily dry-bulb temperature (average of maximum and minimum) falls below 18o Celcius for each calendar day on which such deficiency occurs. (On the Fahrenheit scale, the assumed reference temperature is 65o.)
A measure of how cold a location was over a period of time, relative to a base temperature. In CBECS, the base temperature used is 65 degrees Fahrenheit, and the period of time is one year. The heating degree-day is the difference between that dayâ€™s average temperature and 65 degrees if the daily average is less than 65; it is zero if the daily average temperature is greater than or equal to 65. Heating degree-days for a year are the sum of the daily heating degree-days for days that year.