Heating degree days measure the demand for energy needed to heat a building in a defined region. When temperatures fall below a defined temperature for that region, buildings typically require heating. A heating degree day is represented by the number of degrees that the average temperature falls below the defined temperature.
For example, if the average temperature for a day in a region is defined as 30° F and the degree days reference point temperature for that region is 65° F, the heating degree (day) value for that day is 35. Maintaining this temperature data for regions, helps us understand the relationship between degree days, energy consumption, and the resulting carbon emissions.