A couple of our viewers have asked the weather department for an explanation of heating degree days. So, here it is!
Heating degree days are indicators of household energy consumption for space heating. For an average outdoor temperature of 65 degrees Fahrenheit, most buildings require heat to maintain a 70 degree temperature inside. Basically they are used for calculations relating to the energy consumption required to heat buildings.
Here’s how heating degree days are calculated. Find the day’s average temperature by adding the day’s high and low temperatures and dividing by two. If the number is above 65, there are no heating degree days that day. If the number is less than 65, subtract it from 65 to find the number of heating degree days. Running totals are kept for these units over a time period of a year so fuel distributors and power companies can assess average demands.
For example today’s high was 40 and the low was 32, so the average is 36 degrees. 65 minus 36 is 29 heating degree days.
Cooling degree days are also based on the day's average minus 65. They relate the day's temperature to the energy demands of air conditioning.
The heating degree season begins July 1st and the cooling degree day season begins January 1st.