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Heat Pump Operating Cost Calculator
Quick answer: Seasonal heat need is roughly design heat loss times 24 times heating degree days, divided by the design temperature difference. Divide that by the HSPF2 rating times 1,000 to get kilowatt-hours, then multiply by your electricity rate. The calculator compares that estimate with a gas furnace at your gas price.
How it works
Heating degree days (HDD) measure how cold a season is; your local weather service or utility publishes them. Heat loss scales roughly with the temperature difference, so a house that loses 36,000 BTU/h at a 70°F difference loses about 514 BTU/h per degree. Multiply that by 24 hours and by HDD to estimate the season's heat. HSPF2 is a seasonal rating in BTU of heat per watt-hour, so dividing by HSPF2 × 1,000 gives kilowatt-hours. For gas, divide the heat by furnace efficiency and by 100,000 BTU per therm. Real bills vary with thermostat habits, defrost, backup heat and how your climate compares with the HSPF2 test climate; cold regions often see lower seasonal efficiency than the label. See COP explained and HSPF and SEER explained.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: 36,000 BTU/h heat loss at a 70°F difference, 6,500 HDD, HSPF2 7.5, $0.15/kWh, 95% furnace, $1.30/therm. Heat ≈ 36,000 × 24 × 6,500 ÷ 70 ≈ 80.2 million BTU. Heat pump ≈ 10,700 kWh ≈ $1,605. Gas ≈ 845 therms ≈ $1,098.
FAQ
Why is gas cheaper in the example?
Because of the assumed prices. Change the rates to yours; the answer flips in many areas.
Does this include cooling?
No. It estimates heating only.
Where do I find HSPF2?
On the AHRI certificate or the spec sheet for the exact matched system.
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