TrustyBench

Heat pump vs gas furnace cost and switchover calculator

See which heats your home for less at your prices, and the outdoor temperature where a dual-fuel system should switch to gas.

At 30°F: heat pump $2.05 vs gas $1.47 per 100,000 Btu of heat.

The heat pump costs 38.9% more.

Switchover: 48.8°F (9.4°C). Below this the furnace is cheaper; above it the heat pump is.

Example prices and heat pump are filled in. Replace them with yours.

Heat pump data you have

1. Prices

Use your per-kWh charges: energy plus delivery plus per-kWh riders and taxes. Leave out the fixed monthly customer charge. If you have tiers or time-of-use, use the winter rate you pay at the margin.
Use your per-therm (or per-CCF) charges: gas supply plus delivery plus per-unit riders and taxes. Leave out the fixed monthly customer charge. Annual averages that include fixed charges overstate the price, and summer averages most of all.
On the yellow EnergyGuide label or the furnace spec sheet. 80% is common for non-condensing furnaces. Older or poorly maintained equipment can run below its rating. Enter a lower figure if you know it.

2. Heat pump

COP at 47, 17 and 5°F is on the NEEP cold-climate product list (ashp.neep.org) and on most spec sheets ('extended performance' tables). Use the 'rated' column if there is one.

Optional. Cold-climate models list it. NEEP and ENERGY STAR's cold-climate floor is 1.75 (S7, S8).
Heat pumps lose some output to defrost cycles in cold, damp weather. The DOE test method models this with a lower 35°F point (S4).
I also have heating capacities (more exact)

Use the capacities from the same column (rated or max) as the COPs.

My heat pump has a low-temperature cutout
The outdoor temperature below which your system stops the compressor. It may be a factory limit or a thermostat setting.

3. Where to compare

Break-even

  • Break-even COP: 3.58. The heat pump is cheaper whenever its COP is above this.
  • Break-even electricity price at 30°F: 13.0 ¢/kWh. Below this, the heat pump is cheaper at 30°F.
  • Break-even gas price at 30°F: $1.94 per therm. Above this, the heat pump is cheaper at 30°F.

Cost by outdoor temperature

$0.00$2.00$4.00−20°F0°F20°F40°F60°FOutdoor temperature$ per 100,000 Btuswitchover 48.8°F

The step at 45°F comes from the federal test method: between 17°F and 45°F it assumes the unit loses output to defrost.

How the curve works
  1. Between the rated points the heat pump's output and power change in a straight line with outdoor temperature. This is how the federal test method (10 CFR 430 App. M §4.2.1) builds HSPF.
  2. The 35°F point is estimated with DOE's default for units that were not tested at 35°F (§3.6.4(c)): 90% of the interpolated capacity and 98.5% of the interpolated power. That is about 91% of the interpolated COP. Single-speed units are tested at 35°F (§3.6.1), but their 35°F result is rarely published, so the same default is used for every unit.
  3. Without capacities, the tool draws straight lines through the COPs themselves. This is close to, but not exactly, the federal method, which interpolates output and power separately. Enter capacities for the exact form.
  4. Below 17°F the line through 17°F and 47°F continues, as in the federal method. If you enter COP at 5°F, the tool uses the 5-17°F line instead. That is our extension, not part of App. M.
  5. Where the curve falls below COP 1, the compressor is treated as off and heat comes from electric resistance at COP 1 (App. M eq. 4.2.1-3).
  6. Real units at part load, with ducts and with a particular thermostat will differ from their rated points.

Source: 10 CFR 430 Subpart B, Appendix M, §3.6.4(c) and §4.2.1 (S4).

Cost by temperature

Outdoor °FHeat pump COPHeat pump $/100k BtuGas $/100k BtuBreak-even electricity ¢/kWhCheaper
60°F4.06$1.30$1.4720.4¢Heat pump
48.8°F (switchover)3.58$1.47$1.4718.0¢Same (break-even)
47°F3.50$1.51$1.4717.6¢Gas
35°F2.72$1.94$1.4713.7¢Gas
30°F (your temperature)2.58$2.05$1.4713.0¢Gas
17°F2.20$2.40$1.4711.1¢Gas
5°F1.68$3.14$1.478.4¢Gas
−5°F1.25$4.23$1.476.3¢Gas

Notes

  • Below −10.7°F this curve falls under COP 1. The federal test method treats the compressor as off there (S4), so the table prices backup electric resistance heat.
  • To use this, set your dual-fuel thermostat's compressor lockout (it may be called 'compressor minimum outdoor temperature', 'balance point' or 'switchover') near 49°F. This is the economic point only. If your heat pump cannot keep the house warm above that temperature, the furnace will need to run anyway.
  • These are costs per unit of heat. If you would disconnect gas entirely, you would also stop paying the gas fixed monthly charge, which is not counted here.
  • A furnace's blower uses electricity that this comparison does not count. A heat pump's COP already includes its indoor fan. This tilts the comparison slightly toward gas.
  • Electric resistance heat (backup strips, baseboard) costs $5.28 per 100,000 Btu at your electricity price.
Show your work
Prices
  Electricity: $0.180/kWh
  Gas: $1.40/therm

Constant
  1 therm = 100,000 Btu (EIA). 1 kWh = 3,412.14 Btu (NIST).
  So 100,000 Btu of heat = 100,000 ÷ 3,412.14 = 29.307 kWh of heat.

Gas furnace, per 100,000 Btu delivered
  $1.40 per therm ÷ 0.95 AFUE = $1.47

Heat pump COP at 30°F (federal test-method curve, 10 CFR 430 App. M)
  COP at 35°F (defrost-derated) = 0.90 ÷ 0.985 × [2.20 + 0.6 × (3.50 − 2.20)] = 0.9137 × 2.98 = 2.72
  30°F lies between 17°F and 45°F, so COP = 2.20 + (2.72 − 2.20) × (30 − 17) ÷ (35 − 17) = 2.58

Heat pump, per 100,000 Btu delivered at 30°F
  $0.180 per kWh × 29.307 kWh ÷ 2.58 COP = $2.05

Comparison
  $2.05 ÷ $1.47 = 1.389 → the heat pump costs 38.9% more at 30°F

Break-even
  COP* = electricity × 29.307 × AFUE ÷ gas = 0.180 × 29.307 × 0.95 ÷ 1.40 = 3.58
  Electricity price* = gas × COP ÷ (29.307 × AFUE) = 1.40 × 2.58 ÷ (29.307 × 0.95) = $0.130/kWh (13.0¢)
  Gas price* = electricity × 29.307 × AFUE ÷ COP = 0.180 × 29.307 × 0.95 ÷ 2.58 = $1.94/therm

Switchover (where the heat pump's COP equals 3.58)
  3.58 is above COP at 45°F (3.41), so it falls on the 17-47°F line:
  T = 17 + 30 × (3.58 − 2.20) ÷ (3.50 − 2.20) = 48.8°F (9.4°C)
  Without the defrost dip: T = 17 + 30 × (3.58 − 2.20) ÷ (3.50 − 2.20) = 48.8°F

Calculated with unrounded values, so the last digit may differ from multiplying the rounded numbers shown.
Sources: EIA units and natural gas FAQ; NIST SP 811; 10 CFR 430 Subpart B Appendix M §3.6.4(c) and §4.2.1.

This calculator compares the cost of heat, not your whole energy bill. It uses the prices and efficiencies you enter, U.S. Energy Information Administration and NIST conversion factors, and a simplified heat pump performance curve based on the federal test procedure (10 CFR 430, Subpart B, Appendix M). Real heat pumps and furnaces perform differently from their ratings: part-load operation, defrost, duct losses, installation quality and backup heat all change the result. The switchover temperature is an economic estimate only. It does not check that your heat pump can keep your home warm at that temperature. Utility rates vary by season, tier and time of day, so use your own current rates. Before changing thermostat lockout or auxiliary heat settings, check your equipment and thermostat manuals, and ask your HVAC contractor if you are unsure. This is an estimate, not financial or engineering advice.

How it works

Enter what you pay for one more kWh and one more therm, your furnace's AFUE and your heat pump's COP. The calculator prices 100,000 Btu of delivered heat from each system and finds the COP at which they cost the same. With COPs at 47°F and 17°F it also estimates how COP falls as it gets colder, and reports the outdoor temperature below which gas is cheaper.

How we calculate it

These are the steps in the Show your work panel, in the same order.

  1. Prices. Electricity in $/kWh (¢/kWh ÷ 100). Gas in $/therm. $/CCF is divided by 1.037 and $/Mcf by 10.37, from EIA's 2025 US average of 1,037 Btu per cubic foot. You can enter your own heat content.
  2. Constant. 1 therm = 100,000 Btu (EIA). 1 kWh = 3,412.14 Btu (NIST). So 100,000 Btu of heat = 100,000 ÷ 3,412.14 = 29.307 kWh of heat.
  3. Gas furnace, per 100,000 Btu delivered. Gas price per therm ÷ AFUE (0.95 for 95%).
  4. Heat pump COP at your temperature. At 45°F and above, and below 17°F, COP follows the straight line through your 47°F and 17°F values. Between 17°F and 45°F it follows a line to a lower, defrost-derated 35°F point: 0.90 ÷ 0.985 × [COP17 + 0.6 × (COP47 − COP17)]. That is the federal test method's default (10 CFR 430 App. M §3.6.4(c) and §4.2.1). If you enter COP at 5°F, the 5-17°F line is used below 17°F. If you enter capacities, output and power are interpolated separately and COP = output ÷ (3.41214 × power in watts). Where COP falls below 1, heat is priced as electric resistance at COP 1.
  5. Heat pump, per 100,000 Btu delivered. Electricity price × 29.307 kWh ÷ COP. With HSPF2 only, the seasonal COP is HSPF2 ÷ 3.41214, so the cost is 100 × electricity price ÷ HSPF2.
  6. Comparison. Heat pump cost ÷ gas cost, shown as a percent cheaper or more.
  7. Break-even. COP* = electricity price × 29.307 × AFUE ÷ gas price. At your COP, the break-even electricity price = gas price × COP ÷ (29.307 × AFUE), and the break-even gas price = electricity price × 29.307 × AFUE ÷ COP.
  8. Switchover. The outdoor temperature where the COP curve equals COP*, solved on each straight segment. Below it the furnace is cheaper. A tie goes to gas.

All math uses unrounded values, so the last digit may differ from multiplying the rounded numbers shown.

Worked example (the page default)

Prices
  Electricity: $0.180/kWh
  Gas: $1.40/therm

Constant
  1 therm = 100,000 Btu (EIA). 1 kWh = 3,412.14 Btu (NIST).
  So 100,000 Btu of heat = 100,000 ÷ 3,412.14 = 29.307 kWh of heat.

Gas furnace, per 100,000 Btu delivered
  $1.40 per therm ÷ 0.95 AFUE = $1.47

Heat pump COP at 30°F (federal test-method curve, 10 CFR 430 App. M)
  COP at 35°F (defrost-derated) = 0.90 ÷ 0.985 × [2.20 + 0.6 × (3.50 − 2.20)] = 0.9137 × 2.98 = 2.72
  30°F lies between 17°F and 45°F, so COP = 2.20 + (2.72 − 2.20) × (30 − 17) ÷ (35 − 17) = 2.58

Heat pump, per 100,000 Btu delivered at 30°F
  $0.180 per kWh × 29.307 kWh ÷ 2.58 COP = $2.05

Comparison
  $2.05 ÷ $1.47 = 1.389 → the heat pump costs 38.9% more at 30°F

Break-even
  COP* = electricity × 29.307 × AFUE ÷ gas = 0.180 × 29.307 × 0.95 ÷ 1.40 = 3.58
  Electricity price* = gas × COP ÷ (29.307 × AFUE) = 1.40 × 2.58 ÷ (29.307 × 0.95) = $0.130/kWh (13.0¢)
  Gas price* = electricity × 29.307 × AFUE ÷ COP = 0.180 × 29.307 × 0.95 ÷ 2.58 = $1.94/therm

Switchover (where the heat pump's COP equals 3.58)
  3.58 is above COP at 45°F (3.41), so it falls on the 17-47°F line:
  T = 17 + 30 × (3.58 − 2.20) ÷ (3.50 − 2.20) = 48.8°F (9.4°C)
  Without the defrost dip: T = 17 + 30 × (3.58 − 2.20) ÷ (3.50 − 2.20) = 48.8°F

Calculated with unrounded values, so the last digit may differ from multiplying the rounded numbers shown.
Sources: EIA units and natural gas FAQ; NIST SP 811; 10 CFR 430 Subpart B Appendix M §3.6.4(c) and §4.2.1.

Sources

  1. S1: EIA, Energy Explained, Units and calculators.
  2. S2: NIST SP 811, 2008 edition, Appendix B.
  3. S3: EIA FAQ: converting natural gas prices to $/therm (2025 heat content).
  4. S4: 10 CFR 430 Subpart B, Appendix M.
  5. S5: 10 CFR 430 Subpart B, Appendix M1 (HSPF2).
  6. S6: 10 CFR 430.32(e), furnace AFUE standard.
  7. S7: NEEP Cold Climate ASHP Specification v4.0 and product list.
  8. S8: ENERGY STAR Central AC and Heat Pump Spec v6.1.

Questions

Is a heat pump cheaper to run than a gas furnace?

It depends on one number, the break-even COP: electricity price per kWh × 29.3 × furnace AFUE (as a decimal) ÷ gas price per therm. The heat pump is cheaper whenever its COP is above that. At 18¢/kWh, $1.40/therm and a 95% furnace, the break-even COP is 3.58. A heat pump rated COP 3.5 at 47°F and 2.2 at 17°F only beats it above about 49°F. At 13¢/kWh the break-even drops to 2.59, and the same heat pump wins down to about 30°F.

What outdoor temperature should I set my dual-fuel switchover to?

Set it near the outdoor temperature where your heat pump's COP drops to the break-even COP. The calculator finds it from your unit's COP at 47°F and 17°F, which are on the NEEP cold-climate product list and most spec sheets. Thermostats call the setting compressor lockout, compressor minimum outdoor temperature, balance point or switchover. This is the cheapest point, not a comfort check. If the heat pump cannot keep the house warm above it, the furnace will run anyway.

Which electricity and gas price should I use?

Use the price of one more kWh or therm: supply plus delivery plus per-unit riders and taxes. Leave out the fixed monthly customer charge, because you pay it either way. Dividing the whole bill by usage overstates the price, and gas most of all in summer. With tiered or time-of-use rates, use the winter rate you pay at the margin. The fixed gas charge only goes away if you disconnect gas entirely.

Why did my electric bill jump after installing a heat pump?

Part of it is expected. Heat that used to be on the gas bill is now on the electric bill, so compare the two bills together. Backup resistance strips are the other suspect. They need 29.3 kWh for 100,000 Btu, which costs $5.28 at 18¢/kWh. A heat pump at COP 3 makes the same heat for $1.76. Check the aux-heat lockout setting and how long the strips run.

Can I use HSPF2 instead of COP?

Yes, for a season-average figure. HSPF2 ÷ 3.412 gives the heat pump's average COP over a DOE test climate, including defrost and some backup heat. It cannot give a switchover temperature, because it is one number for the whole season. Do not enter an older HSPF rating instead. HSPF and HSPF2 come from different tests.

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