What dual fuel is
A dual-fuel (hybrid) system pairs an electric heat pump with a gas or propane furnace. The heat pump heats in mild and moderately cold weather; the furnace takes over when it gets colder or when it's cheaper to burn fuel.
The handoff happens at a balance point set on the thermostat or control, based on the heat pump's capacity and local fuel and electricity prices.
Dual fuel vs alternatives
| System | Strength | Trade-off |
|---|---|---|
| Furnace + AC | Simple, strong heat in deep cold | Burns fuel all winter |
| Heat pump + electric strips | All-electric, no gas line | Strip heat is costly in deep cold |
| Dual fuel | Cheapest heat source at each temperature | Two systems to maintain |
| Cold-climate heat pump only | All-electric, efficient in cold | Needs right sizing for design temperature |
Who benefits most
Homes in mixed and cold climates with gas or propane already in place, especially where the AC is due for replacement, since the heat pump replaces the AC.
Propane homes often see the biggest operating savings, because propane is usually more expensive per unit of heat than natural gas.
Installation essentials
- Heat pump sized to the cooling load, with heating capacity reviewed
- Furnace sized by Manual J
- A thermostat or control that supports dual fuel
- Outdoor temperature sensor for the balance point
- Coil matched to the furnace cabinet
- Furnace must never run with the heat pump in heating mode (coil protection)
Setting the balance point
- Find the heat pump's capacity at low outdoor temperatures.
- Compare the cost per unit of heat for electricity and fuel.
- Set the switchover temperature on the control.
- Review comfort after the first cold snap and adjust.
Already have a furnace?
If your furnace is fairly new and your AC is failing, adding a heat pump in place of the AC can create a dual-fuel system without replacing the furnace, provided the controls and coil are compatible.
Dual-fuel FAQs
Does a dual-fuel system need a special thermostat?
It needs one that supports a heat pump with a fossil-fuel backup, or a separate dual-fuel control kit.
What is a typical balance point?
It varies widely with equipment and prices, often somewhere between about 20°F and 40°F.
Next steps
Ready to get it fixed? Call (888) 555-0146 to reach a licensed provider in your area. Related guides:
Busy winter markets: furnace installation in Michigan · furnace installation in Wisconsin · furnace installation in Ohio · furnace installation in Colorado · furnace installation in Utah · furnace installation in Iowa · all states.