How it’s calculated
- Delivered heat = past gas use × old AFUE (or the demand you enter)
- Heat pump seasonal COP = HSPF2 ÷ 3.412
- Heat pump kWh = heat ÷ COP; furnace therms = heat ÷ AFUE
- Cost = energy × your rate
Worked example
800 therms of past gas use in an 80% furnace; compare a 95% furnace and an HSPF2 7.8 heat pump at $0.17/kWh and $1.40/therm.
Inputs
- How do you know your heating need?
- From my past gas use
- Past annual gas use for heating
- 800 therms
- Efficiency of that old furnace (AFUE)
- 80 %
- Annual heat demand (delivered)
- 50 MMBtu
- New furnace AFUE
- 95 %
- Heat pump HSPF2
- 7.8
- Electricity rate
- 0.17 $/kWh
- Natural gas rate
- 1.4 $/therm
Results
- Heat pump yearly cost
- $1,394.87
- Gas furnace yearly cost
- $943.16
- Difference (furnace − heat pump)
- $-451.71
- Heat pump electricity
- 8,205 kWh
- Furnace gas
- 674 therms
- Heat pump seasonal COP used
- 2.29
- Gas price where costs are equal
- 2.07 $/therm
Assumptions and limits
- HSPF2 represents average seasonal performance for a standard climate region; actual COP varies with outdoor temperature.
- Rates are constant all year.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
Is a heat pump cheaper to run than a gas furnace?
It depends on the ratio of your electricity to gas price and the heat pump’s cold-weather efficiency. Enter your own rates — the break-even gas price output shows where the two costs match.
What is HSPF2?
Heating Seasonal Performance Factor (2023 test procedure): seasonal BTUs of heat per watt-hour of electricity. Dividing by 3.412 gives an average COP.