HVAC & Energy
Heating Degree Day Energy Calculator
Estimate seasonal space-heating energy from a constant UA and heating degree days. Compare SI/US results and review the method, assumptions and related references below.
Change any input to update the calculation. Unit changes preserve the physical quantity.
Inputs
Entered seasonal COP or useful/output efficiency fraction; 0.90 for 90%, 3 for seasonal COP 3.
Calculated locally in your browser. No sign-up or input upload.
Results
Estimated useful heating energy
7,200 kWh24.5674 MMBTUInput energy
2,400 kWh8.1891 MMBTUEffective UA
150 W/K284.3451 BTU/(h·°F)Input-energy cost
480 local currencyCalculation breakdown
- Result interpretation
- Estimate seasonal space-heating energy from a constant UA and heating degree days
Assumptions & checks
Constant-UA degree-day approximation using your climate period and building balance point. Solar/internal gains, varying infiltration, schedules and DHW are not separately modeled; not peak-load sizing.
Formula
Estimate seasonal space-heating energy from a constant UA and heating degree days
Worked example
Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.
Inputs
- Effective heat-loss coefficient UA
- 150 W/K
- Heating degree days (matching balance point)
- 2000 K·day
- Seasonal delivered heat / input energy
- 3
- Input-energy price per kWh
- 0.2
Result
- Estimated useful heating energy
- 7,200 kWh
- Input energy
- 2,400 kWh
- Effective UA
- 150 W/K
- Input-energy cost
- 480 local currency
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Technical references for this calculation
Frequently asked questions
What does this result tell me?
Constant-UA degree-day approximation using your climate period and building balance point. Solar/internal gains, varying infiltration, schedules and DHW are not separately modeled; not peak-load sizing.
How can I check the calculation?
Worked example: UA 150 W/K and 2000 K·day gives 7200 kWh useful heat; performance factor 3 gives 2400 kWh input and 480 at tariff 0.20. Review each stated input and unit; use project-specific values rather than treating the editable example as a requirement.
Reference data & method sources
- ASHRAE steady-state heat transfer
Series thermal resistances for homogeneous layers and stated surface films; no framing or thermal bridge model.
- NIST SI conversion factors
SI/US dimensional conversions. Geometry and energy balances are stated explicitly, not attributed to a design standard.