Your heating today
The heat pump
What the heat pump replaces
Over the years
Fill in your gas use, prices and quotes, then click Compare.
Result
Same house, other assumptions
| Scenario | Payback, years | Difference over the period | NPV |
|---|
Year by year
| Year | Gas system | Heat pump | Difference | Cumulative |
|---|
How it is calculated
Heat delivered = therms x 29.3071 kWh per therm x furnace AFUE. The heat pump uses that heat divided by its COP in electricity. Each year the gas system costs therms x gas price (plus any connection fee and the cooling electricity of a new AC) and the heat pump costs its heating electricity plus cooling electricity reduced by the saving you enter; prices rise by the yearly increases. The heat pump's extra up-front cash = its quote plus extra work minus incentives minus what the new furnace and AC would have cost. Payback is the year the cumulative difference turns positive, interpolated within the year. The break-even COP is the seasonal COP at which the yearly heating cost of the two systems is equal.
Not modelled: time-of-use and demand charges, taxes, home value effects, ductwork or comfort differences, refrigerant and equipment lifetimes that differ, and COP that changes with outdoor temperature. Unverified: checked by hand calculation and unit tests only. Use the prices from your own bills and the equipment from your own quotes.
Common questions
Is a heat pump cheaper to run than a gas furnace?
It depends on the ratio of your electricity price to your gas price and on the heat pump's seasonal COP. A heat pump delivers roughly 2 to 3 units of heat per unit of electricity. This tool converts both fuels to cost per million BTU of heat delivered and shows the COP at which the two running costs are equal for your prices.
What is COP and what number should I use?
COP (coefficient of performance) is the heat delivered divided by the electricity used. Use a seasonal average for your climate, not the best-case rating; 2.0 to 3.0 is common in cold and mixed climates and a cautious case is 2.0. The tool re-runs your numbers at COP 2.0 and 20 percent better so you can see the range.
How is the heat pump compared with the gas system?
Against the cost of a new gas furnace and, if you would replace it anyway, a new air conditioner, because a heat pump does both jobs. Enter those installed costs and the extra cash the heat pump needs up front is the difference after incentives and any extra work such as a panel upgrade.
How do I find the therms I burn for heating?
Look at your gas bills. Take the therms used in a summer month as the non-heating base load (water heater, stove), multiply it by twelve, and subtract that from your yearly total. Your furnace's AFUE converts those therms into the heat your home actually receives.
Should I include incentives?
Enter the dollar amount of any rebate or credit you are sure to receive as a reduction of the heat pump's cost. Incentive rules change and differ by location, and this tool does not know which apply to you, so it uses only the number you enter.
Does capping the gas line change the answer?
Yes, if you have no other gas appliances left, the monthly connection fee stops. Enter it and it is counted as a yearly saving. Leave it at zero if you keep gas for a stove, water heater or dryer.
Does it model cold-climate backup heat, time-of-use rates or demand charges?
No. Backup resistance heat is captured only through the seasonal COP you enter. Time-of-use pricing, demand charges, taxes and home value effects are not modelled.
Is my information uploaded anywhere?
No. Everything you type stays in this browser tab. There are no accounts, cookies or analytics vendors.