Degree Days Help Keep You Warm

No matter what the temperature is outside, most retail heating oil companies use the science of degree day measurements to determine when your home needs a fuel delivery, and how much fuel you’re likely to use in a typical heating season from September through May.

What Are Degree Days?

The degree day system was developed by heating engineers who wanted a method to relate each day's temperatures to the demand for fuel to heat and cool buildings.

To calculate the heating degree days for a particular day, retail heating oil dealers find the day's average temperature by adding the day's high and low temperatures and then dividing by two. If the number is above 65, there is no heating degree days that day. If the number is less than 65, dealers subtract it from 65 to find the number of heating degree days.

For example, if the day's high temperature is 60 and the low is 40, the average temperature is 50 degrees. 65 minus 50 equals 15 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. For example, if the day's high is 90 and the day's low is 70, the day's average is 80. 80 minus 65 equals 15 cooling degree days.

Heating and cooling degree days can be used to relate how much more or less you might spend on heating or air conditioning if you move to a new home or move from one part of the country to another. Of course you'd have to take into account how well insulated your new home will be in comparison to your old one, and depending on your heating source, the different costs of heating oil electricity, or gas heat. Records of past heating degree days and records of past energy use are helpful in determining expenditures.

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