When you talk with a fuel oil dealer, at some point in the conversation we’re sure they will mention the words Degree Day. Although that might sound like an alternative rock group, it’s really an important industry term. So, what is a Degree Day and how does it affect your fuel tank?

Degree Day
  A Degree Day is a unit we use for measuring how cold (or hot) it has been over a 24-hour period. This Degree Day affects your fuel tank and helps us determine how much fuel you have burnt for that time period. Whenever the average temperature on a day is below 65º (the base temperature for measuring a Degree Day), you have a Degree Day.
  For example, if on a given day the outdoor high temperature was 70º and the low was 50º, then the average temperature for that day was 60 degrees. That is 5º less than the base temperature of 65º. Therefore, we count 5-degree days for that one-day period.
  Now you might be thinking that each house doesn’t burn the same amount of fuel everyday and you would be correct. To effectively calculate your tank’s burn rate, we also need two more numbers. The first is the tank’s ideal delivery gallons.

Tank Ideal Delivery Gallons
  Considering your tank size, usable gallons and reserve gallons is how we derive your ideal delivery amount. For a typical 275-gallon basement heating oil tank, the ideal delivery amount is generally 200-gallons.

K-Factor
  The last number is called the K-factor. This is simply a number showing how fast a tank uses fuel. Like miles-per-gallon, think of a K-factor as gallons per degree day. If your car gets 20 miles per gallon, and your have a 10 gallon gas tank, you know you can go 200 miles. Likewise, if we know your burner runs at a 5 K-factor, and your ideal fill is 200 gallons, we know you can go 1000 Degree Days.

Putting It All Together
  At Farm & Home Oil, by applying Degree Days, your home's ideal delivery amount and the K-Factor, we ensure that you always have the fuel you need, when you need it. And now, when you are speaking to someone about your heating oil usage you will understand the heating Degree Day system and how it works.

Here are some examples of heating Degree Days at various places
around the USA for an average heating season: