Degree Day archive

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What is a degree day? Simply put, a degree day is a unit used in estimating fuel/electricity requirements for heating or cooling a building.

There are two types of degree days used; Cooling Degree Day and Heating Degree Day. Cooling Degree Days suggest that a building would require some degree of cooling, whereas Heating Degree Days suggest that a building would require some degree of heating.

More extreme numbers representing a particular day's degree days indicate that more energy would be required to heat or cool a building. Energy usage and your electric bill are directly proportional! The more energy you use to heat or cool your home or office, the more you can expect to pay on your electric bill.

Using Degree Day data can help you decide what type of heating/cooling system should be installed in your home or building in terms of price and efficiency, and can also help you determine an annual budget for heating and cooling expenses.

65 degrees Fahrenheit is the base temperature used when determining Degree Days. To determine Degree Days, simply add the day's maximum temperature and minimum temperature, then divide that by two (2), and subtract 65. Negative numbers indicate Heating Degree Days whereas positive numbers indicate Cooling Degree Days.

[((Max Temp + Min Temp)/2) - (65)] = Degree Day(s)

Though this is the official formula, many people (myself included) consider 65 - 70 degrees Fahrenheit to be a better representation of comfortable indoor temperatures. Therefore, no heating or cooling would be required within this range of temperatures. You can adjust the above formula accordingly to determine Degree Days with this (or some other) range.

Photo: Morning haze off the Nile River reduces visibility in Cairo.