Heating Degree Day Calculator

How It Works

Heating Degree Days (HDD) measure how cold your climate is over a year. Each day that the average outdoor temperature is one degree below 65 degrees F counts as one degree day. A day averaging 35 degrees F adds 30 HDD. Miami has about 200 annual HDD; Minneapolis has about 7,800. HDD is the best single number for predicting heating costs because it captures both how cold it gets and how long it stays cold. By multiplying HDD by your home heat loss rate, you get a solid estimate of annual heating energy consumption. You can find your local HDD from the National Weather Service or your utility bill.