Estimate heating degree days from daily high temperature, daily low temperature, base temperature, number of days, and previous accumulated HDD. This calculator is useful for heating demand estimates, energy planning, utility comparisons, and seasonal weather tracking.
High and low temperature:
Enter the daily maximum and minimum temperature for the day or period you want to estimate.
Base temperature:
The base temperature is the outdoor temperature below which heating is assumed to be needed.
Daily HDD:
The calculator averages the high and low temperature, then subtracts that average from the base temperature.
Accumulated HDD:
The calculator can multiply daily HDD by a number of days and add previous HDD to estimate a seasonal total.
A heating degree days calculator is useful for estimating heating demand, comparing cold weather periods, reviewing utility bills, tracking winter severity, planning fuel use, and comparing seasonal weather patterns.
This is a rough weather-based estimate. Real heating energy use depends on building size, insulation, air leaks, thermostat settings, heating system efficiency, solar gain, wind, occupancy, and local conditions.
Your result shows estimated heating degree days for one day, the selected number of days, and the total after adding any previous accumulated HDD. Higher HDD values usually mean colder weather and greater heating demand.
Average the daily high and low temperature, then subtract that average from the base temperature. If the result is below zero, daily HDD is usually counted as zero.
65°F is commonly used in the United States for residential heating degree days, but some efficient buildings may use a lower base temperature.
In most HDD tracking, negative values are set to zero because warm days do not subtract from accumulated heating demand.
No. HDD is a weather-based estimate. Actual energy use also depends on the building, heating system, thermostat, insulation, and occupant behavior.