Course: GFM 102 Technical Aspects of Energy, Resources & Conservation

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Heating Degree Days and Cooling Degree Days Explored

What Is a Degree-Day?

The West North Central region normally requires more heating than other regions.

Data for this figure

Freezing winter weather or a long, sweltering summer — either one increases your utility bills. But how much of the rise in the cost is a result of the weather? You can find out by using a unit of measure called the "degree-day." A degree-day compares the outdoor temperature to a standard of 65°F; the more extreme the temperature, the higher the degree-day number and the more energy needed for space heating or cooling.

Hot days, which require the use of energy for cooling, are measured in cooling degree-days. On a day with a mean temperature of 80°F, for example, 15 cooling degree-days would be recorded. Cold days are measured in heating degree-days. For a day with a mean temperature of 40°F, 25 heating degree-days would be recorded. Two such cold days would result in a total of 50 heating degree-days for the two-day period.

Click here to access Energy Units and Calculators: Degree Days Explained webpage by the U.S. Energy Information Administration.