Heat Pump vs Gas Furnace
Comparing operating cost, comfort, and application so you can spec the right heating system on every job — and explain the trade-offs to the homeowner in plain numbers.
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In This Guide
How Each System Makes Heat
A gas furnace makes heat by combustion. Fuel burns in the heat exchanger, combustion gases vent out the flue, and the blower pushes house air across the hot exchanger. Every BTU of heat comes from a BTU of fuel you burn — a furnace can never be more than 100% efficient, and in practice a high-efficiency condensing unit lands around 90–98% AFUE.
A heat pump doesn't create heat — it moves it. Running the refrigeration cycle in reverse (the reversing valve swaps the roles of the indoor and outdoor coils), it absorbs low-grade heat from outdoor air and rejects it indoors. Because it's pumping existing heat rather than burning fuel, a heat pump routinely delivers 2.5 to 4 units of heat for every unit of electricity it consumes. That's the whole story of why the operating-cost math can favor either system depending on climate and utility rates.
Field note: The heat pump's advantage shrinks as it gets colder outside. There is less heat in 20°F air than in 45°F air, so capacity and efficiency both fall right when the building needs the most heat. That single fact drives balance point, backup heat, and the whole dual-fuel conversation below.
COP, HSPF2, and AFUE Explained
To compare fuels honestly you have to speak in delivered heat, not nameplate ratings. Three numbers do the translating:
- COP (Coefficient of Performance) — heat pump heat output ÷ electrical input, at a given outdoor temperature. A COP of 3.0 means 3 BTU delivered per 1 BTU of electricity. COP is instantaneous and drops as it gets colder.
- HSPF2 — the seasonal heating efficiency rating for heat pumps under the current DOE M1 test procedure. Modern units run roughly 7.5–10 HSPF2. Higher is better; it rolls a whole heating season of varying COP into one figure.
- AFUE (Annual Fuel Utilization Efficiency) — the percentage of fuel energy a furnace turns into usable heat over a season. An 80% AFUE furnace wastes 20% up the flue; a 96% condensing furnace wastes only 4%.
Handy conversion
A furnace's AFUE is just a COP below 1. To compare directly:
Furnace "COP" = AFUE (as a decimal) → 96% AFUE ≈ 0.96
Heat pump COP at 47°F ≈ 3.2, at 17°F ≈ 2.0, at 5°F ≈ 1.5
Operating Cost: A Worked Comparison
The apples-to-apples way to compare is cost per million BTU (MMBTU) of delivered heat. Convert each fuel's price into what it actually costs to put a million BTU into the house.
The two formulas
Electric heat cost ($/MMBTU) = ($/kWh × 293) ÷ COP
Gas heat cost ($/MMBTU) = ($/therm × 10) ÷ AFUE
293 kWh = 1 MMBTU of electricity. 1 therm = 100,000 BTU, so 10 therms = 1 MMBTU.
Assume the customer pays $0.16/kWh for electricity and $1.40/therm for natural gas. Work each system at its real operating condition:
Step 1 — Heat pump at 47°F (COP 3.2)
(0.16 × 293) ÷ 3.2 = 46.88 ÷ 3.2 = $14.65 / MMBTU
Step 2 — Heat pump at 17°F (COP 2.0)
(0.16 × 293) ÷ 2.0 = 46.88 ÷ 2.0 = $23.44 / MMBTU
Step 3 — 96% AFUE gas furnace
(1.40 × 10) ÷ 0.96 = 14.0 ÷ 0.96 = $14.58 / MMBTU
Step 4 — Electric resistance backup (COP 1.0)
(0.16 × 293) ÷ 1.0 = $46.88 / MMBTU
| Heating method | Efficiency | Cost / MMBTU | Verdict |
|---|---|---|---|
| Heat pump, mild (47°F) | COP 3.2 | $14.65 | Cheapest in shoulder season |
| 96% gas furnace | 0.96 AFUE | $14.58 | Flat across all temps |
| Heat pump, cold (17°F) | COP 2.0 | $23.44 | Gas now wins |
| Electric strip heat | COP 1.0 | $46.88 | Most expensive by far |
The takeaway: at these rates the heat pump and the gas furnace are nearly tied in mild weather, but as soon as COP drops toward 2.0 the furnace pulls ahead. Where the two lines cross is the economic balance point — and it moves every time utility rates change. Rerun the numbers with the customer's actual bill; a cheap-gas region and a cheap-electricity region give opposite answers.
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Balance Point and Backup Heat
There are two balance points a good tech keeps straight:
- Thermal balance point — the outdoor temperature where the heat pump's declining capacity exactly equals the building's rising heat loss. Below it, the heat pump alone can't hold setpoint and something has to make up the difference. In a typical build this lands somewhere between 25°F and 35°F.
- Economic balance point — the outdoor temperature where the heat pump becomes more expensive to run than the gas furnace (the crossover from the cost table above). On a dual-fuel system this is where you want the control to switch fuels.
Below the thermal balance point you have two choices for making up the shortfall:
Electric resistance strips
Simple and reliable, but COP 1.0 — the most expensive heat on the table. Fine as emergency or backup heat in a mild climate; punishing on the bill if it carries the load all winter. Size and stage the strips so they only energize when the heat pump truly can't keep up.
Gas furnace (dual fuel)
Pair a heat pump with a gas furnace and let an outdoor thermostat or communicating control switch to gas below the balance point. You get cheap heat-pump BTUs in shoulder season and cheap gas BTUs in a deep freeze — the best of both.
Don't run both at once
On a dual-fuel system the heat pump and gas furnace must never fire together. Warm return air from the furnace raises head pressure and can trip the heat pump on high-pressure or damage the compressor. Proper controls lock out the compressor whenever the gas heat calls. Verify that interlock on every dual-fuel install and service call.
Comfort and Supply Air Temperature
Homeowners judge heating by how the air feels at the register, and this is where the two systems behave very differently.
A gas furnace is sized to a nameplate temperature rise, typically 35–75°F above return air. With 68°F return, supply air comes off around 105–125°F — noticeably warm, short bursts of intense heat. A heat pump delivers a lower, steadier supply temperature, often 90–105°F. That's still above body temperature, so it heats fine, but at the register it can feel "cool" to someone used to a furnace, especially during a defrost cycle when the outdoor unit briefly reverses.
Set expectations up front. The number-one heat-pump comfort complaint is "the air isn't hot." It isn't a fault — it's longer, gentler run cycles at a lower supply temp, which actually hold a more even room temperature than a furnace's on/off blasts. Tell the customer before they call you back.
Airflow matters for both. Confirm roughly 400 CFM per ton and check the furnace's temperature rise against the nameplate — too little airflow drives rise too high and trips the limit; too much airflow drops supply temp and comfort. A quick delta-T reading tells you whether the equipment is actually delivering its rated heat.
How to Choose (Step by Step)
Here's the field method to land on the right system every time:
Step 1 — Confirm the load. Run or verify a Manual J. Size to the building, never to square-footage rules of thumb. Oversizing is the most common install mistake and it kills comfort on both systems.
Step 2 — Pull the rates. Get $/kWh and $/therm off a real utility bill, not an estimate.
Step 3 — Run cost per MMBTU. Use the two formulas above at realistic COPs for the local design temperature. This tells you which fuel is cheaper and where.
Step 4 — Find both balance points. Plot the heat pump's capacity against the building load, and the cost lines against each other, to fix thermal and economic crossovers.
Step 5 — Pick the backup. Mild climate, cheap power, no gas at the house → straight heat pump with strip backup. Gas available and cold winters → dual fuel. Gas cheap and no interest in AC → straight furnace with an AC coil if cooling is needed.
Step 6 — Verify comfort and airflow. After install, check supply temps, temperature rise, and CFM against the nameplate, and set customer expectations on how the heat will feel.
When Each One Wins
Heat pump makes sense when…
- Climate is mild to moderate (design temp above ~20°F)
- Electricity is reasonably priced or gas isn't available
- The home needs cooling too — one system does both
- The customer wants lower carbon and even, gentle heat
- A cold-climate (variable-speed) model can hold capacity down low
Gas furnace makes sense when…
- Winters are long and hard (frequent sub-20°F design temps)
- Natural gas is cheap relative to electricity
- The customer wants hot, fast register air
- Electric service can't easily support strip backup
- Existing gas piping and venting are already in place
For a huge share of the country the honest answer is dual fuel: a heat pump carrying the mild-weather load at a low cost per BTU, with a gas furnace stepping in below the balance point. It costs more up front but delivers the lowest operating cost across a full season and covers you when the temperature falls off a cliff.
Safety reminders
- Any refrigerant work requires EPA Section 608 certification; recover, don't vent.
- New systems increasingly ship with A2L refrigerant (R-454B, R-32) — follow A2L handling, leak-detection, and charge-limit requirements.
- On gas equipment, always verify combustion air, flue integrity, and gas pressure; a cracked heat exchanger or blocked flue is a life-safety issue, not a comfort call.
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