Heating Degree Days
Calculator
Results
- Degree days per day
- 14
- Heating degree days
- 1,680
- Heating energy (kWh)
- 15,120
Energy results
| Degree days per day | 14 |
| Heating degree days | 1,680 |
| Heating energy (kWh) | 15,120 |
formula-map diagram
- Degree days per day
- 14
- Heating degree days
- 1,680
- Heating energy (kWh)
- 15,120
Energy relationship
Formula
HDD = ΔT × days; E = HDD × K= 14
Note
This is a simplified model: it applies the standard equation to the numbers you entered and ignores real-world losses, weather variation, tariff structures and equipment tolerances. Wind power assumes air density 1.225 kg/m³ at ISA sea level and the power coefficient you enter (Betz limit 0.593). Verify with measured data or a professional energy audit before making purchasing decisions.
More in Energy and environment
See all →Frequently asked questions
What exactly is a heating degree day?+
It's a measure of how much and for how long the outdoor temperature was below a base temperature, usually 65°F (18°C), on a given day. One degree day accrues for each degree the average daily temperature falls below that base, so a colder or longer cold spell produces more degree days.
Why is 65°F used as the base temperature?+
65°F is historically the temperature below which most buildings were assumed to need heating, based on typical indoor comfort setpoints and incidental heat gain from occupants and appliances. Some calculators let you adjust the base if your building's heating threshold differs.
How do I use heating degree days to estimate energy costs?+
Multiply degree days by your building's heat loss rate (energy per degree day) to estimate total heating energy needed over a period, then apply your fuel cost per unit of energy. This lets you compare heating demand or costs across different months, years, or locations fairly.
Why do two cities with the same average temperature have different degree day totals?+
Degree days accumulate daily, so a city with wide swings between very cold and mild days can have a different total than one with consistently moderate cold, even if their monthly averages are similar. Degree days capture the cumulative severity of cold, not just the average.
Can heating degree days predict my actual heating bill precisely?+
They provide a strong correlation but not a perfect prediction, since actual usage also depends on thermostat settings, insulation changes, occupancy patterns, and solar or internal heat gains. Degree days are best used for comparing periods or normalizing usage, not as an exact billing forecast.