Heat Pump vs Furnace Calculator

The rating point is 47 degrees, and that is the whole problem

A heat pump is rated for capacity at 47°F outdoor air, because that is the temperature the AHRI test procedure uses for the high-temperature rating. Capacity falls as the outdoor air gets colder, and the fall is not gentle: a standard single-stage unit loses roughly 30 to 40 percent of its 47°F capacity by 17°F, and a cold-climate unit loses much less. Efficiency falls too, though not as sharply.

This is why comparing a heat pump to a furnace on one number is misleading. A furnace's rated output is available at any outdoor temperature — it burns fuel and delivers heat until you turn it off. A heat pump's output is a curve, and whether it can heat your house on the coldest night depends on where your house's load line crosses that curve. That crossing is the balance point, and everything below it is somebody else's job.

What fills in below the balance point

Two things can: electric resistance strip heat inside the air handler, or a furnace in a dual-fuel setup. Strip heat is cheap to install and expensive to run, because it is 100 percent efficient at best. If your load is 43,000 BTU per hour at design temperature and the heat pump delivers 30,000, then 13,000 BTU per hour — 30 percent of the load — is coming from strips on the coldest hours, at roughly a third of the heat pump's efficiency.

That penalty is smaller than it sounds in a mild climate, because design-temperature hours are a small fraction of the season, and larger than it sounds in a cold one. This page therefore puts the backup share on a curve rather than a straight line: a unit delivering 70 percent of the design load covers most of the season itself, and the strips only carry roughly a tenth of the annual heat. It is an approximation of a bin-hour simulation, not a substitute for one, and it is why the heat pump versus furnace answer changes with the map rather than with the equipment brochure.

Dual fuel is usually the right answer in a cold climate

A dual-fuel system pairs a heat pump with a gas or propane furnace and switches between them on outdoor temperature. Above the switchover point the heat pump runs, because its cost per million BTU is lower; below it the furnace runs, because the heat pump's capacity and efficiency have both fallen off. The switchover is set by economics, not comfort, and it usually sits somewhere between 25°F and 40°F depending on the two fuel prices.

The advantage over strips is that the backup is efficient. A 90 percent furnace at 25°F is a better deal than a heat pump at 25°F running at a COP of 1.8 with 17 cents electricity, and much better than strips. The disadvantage is that you own and maintain two appliances, and you keep paying the gas connection charge all year.

Why a heat pump feels different, even when it is working

Supply air from a heat pump is typically 90°F to 110°F; from a gas furnace it is 120°F to 140°F. The heat pump therefore runs longer at a lower temperature, which is more efficient and more even, but it feels like a draft to anyone used to a furnace blast. The complaint is real and the system is not broken. Sizing the heat pump to the cooling load rather than the heating load, and accepting that the coldest 1 percent of hours are covered by backup, is what makes it comfortable.

Defrost cycles compound the impression. In humid, near-freezing weather the outdoor coil frosts, and the unit periodically reverses to melt it — during which it appears to be running an air conditioner. Visible steam, a whoosh, and a few minutes of cool air are normal. A furnace has no equivalent, which is one reason heat pump complaints cluster in the 30s rather than at 5°F.

What the comparison should include

Operating cost is the start, not the end. A heat pump also replaces the air conditioner, so the honest comparison is a heat pump plus no AC against an AC plus a furnace — which narrows the price gap considerably, and often reverses it once a failing AC is part of the picture. Add any state or utility rebate, because the federal 25C credit ended for equipment placed in service after December 31, 2025 and is no longer part of the arithmetic. Then add the fixed gas connection charge you would drop if the house went all-electric, which is $120 to $360 a year and never appears in a per-BTU table.

What should not be included is a claim about resale value or "energy independence". Neither is measurable here, and both are the kind of thing that turns a calculation into a sales pitch.

Frequently asked questions

Will a heat pump work in a cold climate?

A standard heat pump will heat a house in a cold climate, but its capacity and efficiency fall as the outdoor temperature drops, so below the balance point something else has to run. A cold-climate heat pump rated to keep most of its capacity at 5°F changes that calculation, and a dual-fuel setup with a furnace as backup changes it further.

What is a balance point?

The outdoor temperature at which the heat pump's delivered capacity exactly equals the house's heating load. Above it the heat pump keeps up on its own; below it, backup heat makes up the difference. It is a property of the equipment and the house together, not of either alone.

Is strip heat as expensive as people say?

It is 100 percent efficient, so it costs whatever a kilowatt-hour costs — about $50 per million BTU at 17 cents, against $19 for a heat pump at a seasonal COP of 2.6. It is fine as occasional backup and expensive as a primary heat source.

Should I switch to a heat pump if I have cheap gas?

Probably not for operating cost alone. At $1.10 a therm and 80 percent AFUE, gas delivers a million BTU for about $14, and a heat pump at 17 cents and a COP of 2.6 costs about $19. The case for the heat pump improves with expensive gas, cheap electricity, a rebate, or an air conditioner that also needs replacing.

Does a heat pump need a different duct system?

It moves more air per ton of capacity than a furnace, and heat pumps are less forgiving of low airflow than gas furnaces are, so an undersized or leaky duct system hurts a heat pump more. Static pressure and return capacity matter more, not less, after the switch.

Why does my heat pump blow cool air sometimes?

Either it is in defrost, which happens in humid near-freezing weather and lasts a few minutes, or the supply temperature is simply lower than a furnace's — 90°F to 110°F rather than 120°F to 140°F. The second is normal operation, not a fault.

Is there still a federal tax credit for a heat pump?

No, not for equipment placed in service after December 31, 2025. Section 25C and Section 25D both ended on that date, so a 2026 installation gets nothing from the IRS. State and utility rebates still exist in many states and are worth checking by address.

Disclaimer: This tool estimates annual heating cost for planning purposes. It uses seasonal efficiencies and a simple capacity-to-load ratio for the balance point, not a bin-hour simulation, and it excludes equipment cost, maintenance and financing.

Last reviewed: October 30, 2026 · Sources: AHRI 210/240 (HSPF2, capacity at 47°F and 17°F), DOE 2023 heat pump standards, ACCA Manual S balance-point method