Multiply Your Electricity-to-Gas Price Ratio by 23: That's the COP a Heat Pump Needs to Beat an 80% Gas Furnace
The question of whether a heat pump is cheaper to run than a gas furnace has a one-line answer, and it’s on your bills. Take your all-in electricity price per kWh, divide it by your gas price per therm, multiply by 29.3 and by your furnace’s efficiency. That’s the seasonal COP a heat pump needs just to tie.
The 29.3 is unit conversion: a therm is 100,000 Btu and a kWh is 3,412 Btu, so a therm holds 29.3 kWh of heat. An 80% furnace delivers 23.4 kWh of heat from each therm, which is where the “times 23” in the title comes from.
The break-even across 20 price pairs
We ran the Heat Pump vs Furnace calculator across five electricity prices and four gas prices for an 80% AFUE furnace. The bold cell is EIA’s October 2026 Short-Term Energy Outlook national forecast for winter 2026-27: 18.25¢ a kWh and $13.84 per thousand cubic feet, which is $1.336 a therm at EIA’s 1,036 Btu per cubic foot.
| Electricity ↓ / Gas → | $1.00/therm | $1.336/therm | $1.60/therm | $2.00/therm |
|---|---|---|---|---|
| 12¢/kWh | 2.81 | 2.11 | 1.76 | 1.41 |
| 15¢/kWh | 3.52 | 2.63 | 2.20 | 1.76 |
| 18.25¢/kWh | 4.28 | 3.20 | 2.67 | 2.14 |
| 22¢/kWh | 5.16 | 3.86 | 3.22 | 2.58 |
| 30¢/kWh | 7.03 | 5.26 | 4.40 | 3.52 |
Read it against what heat pumps actually average over a season. HSPF2 divided by 3.412 gives seasonal COP: the federal minimum of 7.5 HSPF2 is 2.2, and ENERGY STAR’s 8.1 for ducted systems is 2.37. So at the national forecast, a typical new heat pump costs more to run than an old 80% furnace. The calculator puts it at $211 more a year for the average gas-heated home’s 44.9 million Btu of gas (EIA RECS 2020).
The table also shows where heat pumps win against gas: the top-right corner, where electricity is cheap relative to gas. A ratio below about 0.1 (12¢ against $1.20, say) brings the break-even down to about 2.3, which a good heat pump clears.
A 95% condensing furnace raises every number by 19%. At the national forecast, its break-even is 3.8.
Why the answer is often “yes” anyway
Running cost is only one line. Three things change the decision for gas homes:
- The air conditioner. A heat pump is also an air conditioner. If your AC is near the end of its life, the extra cost of a heat pump over a furnace plus a new AC can be small, and a modest running-cost penalty may be worth paying.
- Dropping gas entirely. If water heating and cooking go electric too, the monthly gas customer charge disappears. That’s a fixed sum that can tip a near-tie.
- Rebates. The 30% federal credit for heat pumps (Section 25C) ended for equipment placed in service after December 31, 2025, but some states and utilities still offer their own, which cut the upfront side of the comparison.
Where this doesn’t apply
- Your prices aren’t the national average. Use the per-unit totals from your bills, including delivery charges, for both fuels.
- Cold climates. On the coldest days a standard heat pump’s COP drops and backup resistance heat (COP 1) may kick in. A cold-climate model rated for 5°F holds up better. Use a lower seasonal COP if your winters are harsh.
- Propane, oil and electric resistance. The break-even is far lower: about 1.6 for propane and 1.1 for heating oil at this winter’s forecast prices, and 1.0 for resistance heat. Almost any heat pump wins on running cost.
- Time-of-use electricity rates. If your utility charges more on winter evenings, use the rate you’d actually pay when heating runs.
- Fixed charges in your gas price. The all-in price per therm includes the customer charge spread over your usage. If you keep gas for other things, the marginal price per therm is lower, which raises the break-even.
What to actually do
- Divide your all-in electricity price per kWh by your gas price per therm, using the same month’s bills.
- Multiply by 29.3 and by your furnace’s AFUE (0.8 for most standard furnaces, 0.95 for condensing).
- Compare with the HSPF2 of the heat pump you’re quoted, divided by 3.412, and lower it if your winters are cold.
- If the heat pump is below the break-even, check whether you need a new air conditioner anyway or could drop gas service. Those decide most close calls.
- Run your numbers in the calculator, and see which other upgrades pay back fastest before spending on the big one. If you’re also weighing solar, how the end of the federal credit changed its payback is worth reading first.
Quick answers
Is a heat pump cheaper to run than a gas furnace?
Only if its seasonal COP is above the break-even for your prices: 29.3 × (electricity $ per kWh ÷ gas $ per therm) × furnace efficiency. At EIA's October 2026 national forecast for winter 2026-27, 18.25¢ a kWh and $1.336 a therm, that is 3.2 for an 80% furnace and 3.8 for a 95% one, above most heat pumps' seasonal average.
Where does the 29.3 come from?
A therm is 100,000 Btu and a kWh is 3,412 Btu, so one therm holds 29.3 kWh of heat. A furnace turns a therm into 29.3 × AFUE kWh of heat; a heat pump turns one kWh of electricity into COP kWh of heat. Setting the costs equal gives COP = 29.3 × AFUE × electricity price ÷ gas price.
What seasonal COP do heat pumps actually get?
Seasonal COP is roughly HSPF2 ÷ 3.412. The federal minimum for split systems is 7.5 HSPF2 (COP 2.2) and ENERGY STAR asks for 8.1 for ducted systems (2.37). HSPF2 is rated for a moderate climate, so colder climates average lower.
Does this apply to propane or oil heat?
The same method works with their heat content (91,452 Btu per gallon of propane, 137,381 for heating oil, per EIA), but the break-even is far lower: about 1.6 for propane and 1.1 for oil at this winter's forecast prices, so almost any heat pump wins on running cost.