Enter the heating degree days and fuel used (or the K-factor) into the calculator to determine the heating K-factor.

Heating K Factor Calculator

Enter any 2 values to calculate the missing variable

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Heating K Factor Formula

The following formula is used to calculate the heating K-factor for a given set of variables.

K = \frac{HDD}{F}

Variables:

  • K is the heating K-factor (degree days per unit of fuel)
  • HDD is the heating degree days for the period (degree-days)
  • F is the fuel used during the same period

To calculate the heating K-factor, divide the heating degree days by the fuel used.

What is a Heating K Factor?

The heating K-factor (often used in heating oil/propane delivery calculations) is the number of heating degree days per unit of fuel used over a period (for example, °F·day per gallon). A higher K-factor means fewer gallons (or liters) are used per degree day, and a lower K-factor means more fuel is used per degree day. It’s a practical indicator of weather-normalized fuel consumption and can help estimate future deliveries and spot changes in building heat loss or system performance (it is not a direct measure of equipment efficiency by itself).

How to Calculate Heating K Factor?

The following steps outline how to calculate the Heating K Factor.

  1. First, determine the heating degree days (HDD) for the time period (using the same HDD base temperature your source uses, such as 65°F / 18°C).
  2. Next, determine the fuel used (F) during the same time period.
  3. If you already know K from a prior period, you can solve for fuel used (F) or heating degree days (HDD) by rearranging the formula.
  4. Finally, calculate the Heating K Factor using the formula K = HDD / F (or rearranged as HDD = K × F and F = HDD / K).
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Heating Degree Days (HDD) = 1500 °C·day

Heating K-Factor (K) = ?

Fuel Used (F) = 300 liters