Heat Pump vs Gas Furnace Lifecycle Calculator
Lifecycle Cost Comparison
| Period | Gas System↕ | Heat Pump↕ | Savings↕ |
|---|---|---|---|
| Annual | $777.00 | $1,271.00 | -$494.00 |
| 10 Years | $7,766.00 | $15,707.00 | -$7,941.00 |
| 15 Years | $11,650.00 | $22,061.00 | -$10,411.00 |
| 20 Years | $15,533.00 | $28,414.00 | -$12,881.00 |
Annual Cost Breakdown
Gas System
Heating: $750.00
Cooling: $27.00
Heat Pump
Heating: $1,250.00
Cooling: $21.00
This calculator compares the lifecycle cost of an air-source heat pump against a gas furnace for your climate zone, modeling how a heat pump's efficiency drops as outdoor temperatures fall. It estimates the annual heating and cooling energy each system uses from heating and cooling degree days, prices that energy at your gas and electric rates, and then projects 10-, 15-, and 20-year costs plus the payback period. The result tells you whether electrifying your heating pays off where you live.
Formula
COP(T) = (HSPF ÷ 3.412) × (1 − 0.02 × (47 − T)), with a floor of 1.0
- HSPF
- Heating Seasonal Performance Factor of the heat pump (BTU/Wh)
- 3.412
- BTU per watt-hour, converting HSPF to a rated coefficient of performance
- T
- Average outdoor temperature during the heating season (°F) for the zone
- COP
- Coefficient of performance: heat delivered per unit of electricity used
How it works
- Pick your climate zone (1 warmest to 8 coldest) and enter equipment ratings: gas furnace AFUE, heat pump HSPF and SEER, plus your gas ($/therm) and electric ($/kWh) rates.
- The calculator scales an annual heating and cooling load from the zone's degree days, derives a seasonal COP from the HSPF and average winter temperature, and computes each system's annual energy cost.
- It adds your upfront cost difference, panel upgrade, and IRA credit, then projects multi-year lifecycle costs and the payback period from annual savings.
Worked example
A warm zone 3 home with a 90% AFUE furnace versus an HSPF 10, SEER 18 heat pump, gas at $1.50/therm and electricity at $0.13/kWh.
- Seasonal COP ≈ (10 ÷ 3.412) × (1 − 0.02 × (47 − 38)) ≈ 2.4.
- Annual cost: gas furnace + AC ≈ $438; heat pump heating + cooling ≈ $406.
- The heat pump saves about $32 a year, giving lower 15-year lifecycle cost (≈ $6,097 vs ≈ $6,572).
In this mild climate the heat pump comes out ahead, with roughly $475 in net savings over 15 years.
Frequently asked questions
- What is COP and why does it change with temperature?
- COP, the coefficient of performance, is the heat delivered per unit of electricity consumed. A heat pump works harder to extract heat from cold air, so its COP falls as the outdoor temperature drops, which is why colder climate zones see smaller savings.
- Why might a heat pump cost more in a cold climate?
- In cold zones the seasonal COP can fall toward 1.5, so each unit of heat needs more electricity. If electricity is expensive relative to gas, the heat pump's annual running cost can exceed the gas furnace, lengthening or eliminating the payback.
- What is the IRA credit field for?
- It lets you subtract any Inflation Reduction Act or similar incentive from the upfront cost of switching. A larger credit reduces the net investment and shortens the payback period.
- How accurate is the energy estimate?
- It is a planning estimate built from typical degree-day loads and a simplified seasonal COP, not a full Manual J load calculation. Real bills depend on insulation, air sealing, thermostat habits, and your home's actual size.