Definition
A dual-fuel system, or hybrid heat pump, pairs an electric heat pump with a gas or propane furnace sharing the same ductwork and controls. The heat pump handles all cooling and heating in milder weather; below a set switchover temperature, the controls shut the heat pump off and run the furnace instead. The two normally do not heat together.
Also called: Dual-fuel heat pump, Hybrid heat pump
Why it matters to you.
Central Kentucky winters are mostly mild with occasional hard cold snaps, so a dual-fuel setup lets the heat pump carry most heating hours while the furnace takes the coldest nights. It works with natural gas in Danville and other towns and with propane on rural properties in Boyle, Mercer, Lincoln, Garrard and Jessamine counties.
Practical guidance.
Ask your installer what switchover temperature they will set, why, and whether your fuel is natural gas or propane changes it. Thermostat configuration, refrigerant work and gas-side work are licensed-technician tasks; keeping CO alarms working is the homeowner's job with any fuel-burning furnace.
How does a dual-fuel system decide when to switch to the furnace?
An outdoor temperature sensor and the thermostat or control board switch from heat pump to furnace at a switchover temperature the installer sets. It is usually based on the balance point, where the heat pump can no longer keep up, or on an economic point, where the furnace becomes cheaper to run given local electric and fuel prices. You do not have to choose manually.
Does dual-fuel work with propane on a rural Kentucky property?
Yes. A dual-fuel system can pair the heat pump with a propane furnace as well as a natural gas furnace, which suits rural homes outside gas service areas. Because propane and natural gas are priced differently, the economic switchover temperature may differ between the two, so ask the installer to set it for your fuel and your utility rates rather than a factory default.
Can I add a heat pump to my existing furnace?
Often, yes. An add-on heat pump replaces the outdoor air conditioner and its indoor coil, and the existing furnace becomes the backup heat. It makes sense when the furnace is in good condition and its blower and controls are compatible. The coil sits downstream of the furnace heat exchanger, which is one reason the heat pump and furnace do not run at the same time.
Will a dual-fuel system heat my home during a power outage?
No. Both halves need electricity. The heat pump is electric, and a modern gas or propane furnace still needs power for its blower, igniter, inducer motor and controls. During a winter outage, neither will run without a properly installed generator or transfer switch, so plan backup power separately and never run a portable generator indoors or in a garage.
How is dual-fuel different from a heat pump with electric backup strips?
Both use a heat pump for most heating. The difference is the backup: an all-electric system uses resistance heat strips in the air handler, which turn electricity directly into heat, while dual-fuel uses a gas or propane furnace. Which suits your home depends on whether you already have fuel service, ductwork and a sound furnace, and on local energy prices.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.