Quick answer
A dual-fuel heat pump is a heating system that pairs an electric air-source heat pump with a gas, propane or oil furnace, using the heat pump in mild weather and switching to the furnace below a set outdoor temperature, so each runs when it is cheaper or better able to meet the load.
It is also called a hybrid heat pump. The switch point is a setting, and choosing it well is most of what makes the system pay off.
Quick facts
The key facts about Dual-Fuel Heat Pump, with sources:
- Also called
- Hybrid heat pump, dual fuel system, add-on heat pump
- Parts
- Outdoor heat pump, indoor coil on a furnace, compatible thermostat or control
- Heat pump rating
- HSPF2 (federal minimum 7.5 for split) 4
- Furnace rating
- AFUE (federal minimum 80% for indoor gas furnaces) 4
- Key setting
- Switchover (balance point) outdoor temperature
Key takeaways
- Dual fuel = heat pump plus furnace, with a control that picks one based on outdoor temperature.
- The switch point should come from two things: when the heat pump can no longer keep up, and when gas becomes cheaper per unit of heat.
- With January 2026 US average prices, a heat pump beats a 95% furnace only above a COP of about 3.6, and an 80% furnace above about 3.0 1 2.
- Local prices vary widely, so the right switch point varies too.
- The furnace also serves as backup if the heat pump fails, and it replaces electric strip heat.
What a dual-fuel system is
A dual-fuel system has two heat sources sharing one set of ducts. The heat pump moves heat in from outdoor air using electricity. The furnace burns gas, propane or oil. The heat pump’s indoor coil sits on top of the furnace, and the furnace blower moves air for both.
Only one heats at a time in most setups. Above the switch point, the heat pump runs. Below it, the control locks the heat pump out and runs the furnace. In summer, the heat pump runs as an air conditioner.
Dual fuel is common as a retrofit: a home with a working furnace replaces its old air conditioner with a heat pump, and gains efficient heat for much of the winter without removing gas.
How the system decides which to run
- Outdoor sensor reads the temperature → control compares it with the switch point
- Above the switch point → heat pump heats
- Below the switch point → heat pump locks out, furnace heats
- Heat pump defrost on some setups → furnace may run briefly to temper air
- Summer → heat pump cools; furnace blower moves the air
Two kinds of balance point
The thermal balance point is the outdoor temperature where the heat pump’s output equals the home’s heat loss. Below it, the heat pump cannot keep up alone. See balance point temperature.
The economic balance point is the temperature where heat from the heat pump costs the same as heat from the furnace.
It depends on the heat pump’s COP at that temperature, the furnace’s AFUE, and your electricity and fuel prices.
One kWh is 3,412 BTU, and one cubic foot of natural gas is about 1,036 BTU 3, which lets you put both on the same scale.
A good switch point is the higher of the two. Running the heat pump below its thermal balance point means the house cannot stay warm; running it below its economic balance point means you pay more than you need to.
Sources: [3]
Worked example: finding the switch point with EIA prices
Prices: US residential average electricity 17.45¢/kWh and natural gas $13.96 per thousand cubic feet, both January 2026 1 2. Gas heat content 1,036 BTU per cubic foot; 1 kWh = 3,412 BTU 3. Heat pump COPs are example spec-sheet values.
| Step | Math | Result |
|---|---|---|
| Gas cost per million BTU of fuel | $13.96 ÷ 1.036 | $13.47 |
| Delivered gas heat, 95% AFUE furnace | $13.47 ÷ 0.95 | $14.18 per million BTU |
| Delivered gas heat, 80% AFUE furnace | $13.47 ÷ 0.80 | $16.84 per million BTU |
| Electric heat at COP 1 | 293.1 kWh × $0.1745 | $51.14 per million BTU |
| Break-even COP vs 95% furnace | $51.14 ÷ $14.18 | about 3.6 |
| Break-even COP vs 80% furnace | $51.14 ÷ $16.84 | about 3.0 |
| Example heat pump COP: 3.8 at 47°F, 3.2 at 35°F, 2.4 at 17°F | Interpolate to the break-even COP | Switch near 43°F (95% furnace) or 31°F (80% furnace) |
At these national averages, the heat pump is cheaper than a 95% furnace only on mild days, and cheaper than an older 80% furnace down to about freezing.
Change the prices and the answer moves a lot: cheaper power or pricier gas or propane pushes the switch point colder.
Then check the thermal balance point from your load calculation, and set the higher of the two.
Use your own bills with the heat pump vs furnace tool and see our electric vs gas price ratio research.
Dual-fuel setups
| Setup | How it works | Notes |
|---|---|---|
| Ducted heat pump + gas furnace | Most common; coil on furnace | Needs dual-fuel-capable thermostat or control |
| Heat pump + propane furnace | Same as gas | Propane prices often push the switch point colder |
| Heat pump + oil furnace | Same idea | Less common; check control compatibility |
| Ductless heads + existing boiler or furnace | Two separate systems | Controls usually not linked; set by habit or thermostats |
| Communicating hybrid system | Maker’s control picks the source | May use price and temperature inputs |
Dual fuel vs other heating choices
| System | Backup heat | Strength | Watch for |
|---|---|---|---|
| Dual fuel | Gas, propane or oil furnace | Cheapest source at each temperature | Two systems to maintain |
| Heat pump + electric strips | Resistance heat (COP 1) | Simple, no fuel line | High cost when strips run |
| Cold-climate heat pump | Often small or none | All-electric in cold climates | Check 5°F capacity |
| Furnace + AC | n/a | Familiar | No efficient heat from electricity |
| Geothermal | Often strips | Steady high COP | Loop cost |
Where dual fuel shows up
- On quotes as "hybrid," "dual fuel," or "heat pump on existing furnace."
- In thermostat settings: balance point, heat pump lockout, auxiliary lockout.
- On AHRI certificates for the heat pump and coil, with the furnace listed for airflow 7.
- In utility and state programs; some rebates treat dual fuel differently from all-electric heat pumps. Check heat pump rebates.
Benefits and drawbacks
Benefits
- Uses the cheaper heat source at each temperature.
- Furnace covers the coldest days without costly strips.
- Backup if either system fails.
- Easy retrofit when the furnace is still sound.
Drawbacks
- Keeps a gas or propane connection and its fixed charges.
- Two systems to service.
- Savings hinge on the right switch point.
- Rebates may favor all-electric systems.
Limits and catches
The economic switch point moves with prices, which change month to month. EIA’s monthly residential gas price ran from $13.96 in January to $26.45 in July 2026 2, though heating season prices are what count. Revisit the setting each fall.
Fixed gas service charges are not in the per-BTU math. If you keep gas only for the furnace, those charges change the comparison. And the AC coil on top of an old furnace must still be a certified match for the heat pump’s rating to apply.
Cost drivers and lifespan
Costs depend on whether the furnace stays, the heat pump size and efficiency, coil and line set work, thermostat or control, and electrical capacity. A furnace near the end of its life changes the math; see the repair or replace calculator.
HyreHVAC publishes no equipment prices without enough dated quotes. Compare running costs on the heat pump vs gas furnace cost page.
Setting up a dual-fuel system
- Run a Manual J load to find the heating load at your design temperature.
- Get the heat pump’s capacity and COP at several temperatures from the spec sheet.
- Find the thermal balance point (capacity meets load).
- Find the economic balance point with your prices, as in the example.
- Set the switch point at the higher of the two; set an aux lockout so strips do not run.
- Confirm the furnace blower provides the airflow the heat pump needs.
Gas, refrigerant and electrical work are for licensed professionals; refrigerant handling requires EPA Section 608 certification.
Maintenance
- Spring check for the heat pump’s cooling side; fall check for both heat pump and furnace 8.
- Furnace combustion and heat exchanger checks each fall 8.
- Change filters on schedule; one filter serves both.
- Revisit the switch point setting when your rates change.
Sources: [8]
Warning signs
- Furnace runs on mild days: switch point may be set too high.
- House cold on cold days with heat pump running: switch point too low.
- Electric strips running when a furnace is present: check aux lockout.
- Carbon monoxide alarm or gas smell: leave and call 911 or the gas utility.
Rules and standards
Each half meets its own federal standard: the heat pump’s SEER2 and HSPF2 (14.3 and 7.5 minimum for split systems) and the furnace’s AFUE (80% today for indoor gas furnaces, 95% codified for units made from 18 December 2028) 4.
ENERGY STAR rates them separately: 7.8 HSPF2 for a split heat pump and 95–97% AFUE for gas furnaces 5 6. Gas piping and venting follow local fuel gas codes, which vary.
Misconceptions
- Myth Dual fuel always saves money.
- Reality Only with a switch point set from your own prices and equipment.
- Myth The heat pump should run until it cannot keep up.
- Reality It may be cheaper to switch earlier if gas is cheap.
- Myth Dual fuel needs two duct systems.
- Reality One duct system and one blower serve both.
- Myth Any thermostat works.
- Reality It needs dual-fuel control or the maker’s system control.
Prices and climate vary by state
The switch point depends on local electricity and gas prices and on winter temperatures. A state with cheap power and long mild winters, such as Washington or North Carolina, favors more heat pump hours; a cold state with cheaper gas, such as Ohio, may switch earlier. Check your state page and degree days.
Is dual fuel right for you?
Dual fuel suits homes with a sound gas or propane furnace, cold winters, or gas prices low enough that the furnace wins on the coldest days. An all-electric cold-climate heat pump suits homes leaving gas entirely.
Next step: run your numbers in the heat pump savings calculator.
Questions about Dual-Fuel Heat Pump
What is a dual-fuel heat pump?
A dual-fuel heat pump is a heating system that combines an electric heat pump with a gas, propane or oil furnace. The heat pump heats in mild weather and the furnace takes over below a set outdoor temperature. In summer the heat pump cools. It is also called a hybrid heat pump.
At what temperature should a dual-fuel system switch to gas?
At the higher of two points: where the heat pump can no longer meet your home’s heat loss, and where gas heat becomes cheaper than heat pump heat at your prices. With January 2026 US averages, our example switched near 43°F against a 95% furnace. Your prices and equipment will change it.
Is dual fuel cheaper than an all-electric heat pump?
It can be in cold climates where gas is cheap, because the furnace replaces costly electric strip heat on the coldest days. Fixed gas service charges cut into the savings. An efficient cold-climate heat pump may come close without a gas line. Compare with your own bills.
Can I add a heat pump to my existing furnace?
Often, yes. A heat pump can replace an old air conditioner and sit on the existing furnace as a dual-fuel system. The furnace must provide enough airflow, the coil must be a certified match, and the thermostat must support dual fuel. A contractor should check the furnace’s condition first.
Do both systems run at once?
Usually not. Most dual-fuel controls lock the heat pump out when the furnace runs, because hot furnace air across the heat pump coil can cause high pressures. Some systems briefly run the furnace during defrost to temper air. The maker’s instructions set the sequence.
What thermostat do I need for dual fuel?
One that supports dual-fuel or hybrid heat, with an outdoor temperature input or a setting for heat pump lockout, or the maker’s communicating control. It should also let you lock out electric strip heat. Many common smart thermostats support it.
How do I calculate the economic balance point?
Work out the cost of a million BTU from gas: price per thousand cubic feet ÷ 1.036 ÷ AFUE. Then the cost from electricity: 293.1 kWh × price per kWh ÷ COP. The temperature where the heat pump’s COP makes those equal is the economic balance point.
Does dual fuel work with propane?
Yes. A heat pump paired with a propane furnace works the same way. Propane often costs more per BTU than natural gas, which pushes the economic switch point colder, so the heat pump runs more of the winter. Use your propane price per gallon and 91,452 BTU per gallon in the math.
Sources
- U.S. EIA, Electric Power Monthly, Table 5.3 Average price of electricity by sector, monthly (January 2026 residential), retrieved .
- U.S. EIA, U.S. Price of Natural Gas Delivered to Residential Consumers (monthly), retrieved .
- U.S. EIA, Energy Explained: British thermal units (Btu), retrieved .
- eCFR, 10 CFR 430.32 Energy and water conservation standards (current text), retrieved .
- ENERGY STAR, Air-Source Heat Pumps key product criteria, retrieved .
- ENERGY STAR, Furnaces key product criteria, retrieved .
- AHRI Directory of Certified Product Performance, retrieved .
- ENERGY STAR, Maintenance Checklist for heating and cooling, retrieved .
Expert review
Written by the HyreHVAC Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Switchover arithmetic uses EIA’s January 2026 US residential electricity (Table 5.3) and natural gas prices and EIA heat contents, shown step by step; heat pump COPs are labelled example values. Standards from 10 CFR 430.32 and ENERGY STAR criteria pages.
Suggest a correction. We fix errors and say what changed.