Dual-fuel heat pump systems: should you keep gas as backup in the PNW?

What is a dual-fuel heat pump?

A dual-fuel (sometimes called "hybrid") heat pump system uses an electric heat pump as the primary heat source. When the outdoor temperature drops below a setpoint (usually called the "switchover temperature" or "balance point") the system shuts down the heat pump and switches to the gas furnace, which can also be set up to burn propane.

The switchover is automatic, handled by the thermostat. Common balance points:

• 30°F, aggressive electric prioritization, used when electricity is cheap and gas is expensive
• 35°F, a middle setting
• 40°F, conservative, gas-favored, used when gas is cheap or with older heat pumps that lose capacity below 40°F

The thermostat needs to be dual-fuel capable. The Nest Learning Thermostat, the ecobee Premium and American Standard AccuLink Platinum controls handle this. Some basic thermostats do not.

Dual-fuel heat pump with propane instead of natural gas.

A propane dual-fuel system pairs a heat pump with a furnace that burns propane from a tank. In Clark County the heat pump should carry nearly all of the heating: at EIA's 2024 average Washington residential propane price (about $2.41 a gallon), a 95% AFUE propane furnace costs about $27.68 per million BTU of heat, against $10.30 for a cold-climate heat pump at 25°F on Clark PUD power.

• EIA's newest Washington figure is the 2024 average residential propane price: $26.30 per million BTU, about $2.41 a gallon at 91,452 BTU per gallon. (EIA's weekly propane survey does not cover Washington.)
• At 95% AFUE, that is $27.68 per million BTU delivered.
• The heat pump at 8.79¢/kWh: $10.30 per million BTU at COP 2.5 (2.5 units of heat per unit of electricity, at 25°F), $12.88 at COP 2.0 (15°F), and $25.76 at COP 1.0, the efficiency of plain resistance heat.

The break-even COP is about 0.93, below even resistance heat, so at that price propane is never the cheaper fuel in a Vancouver winter. Set the switchover at the coldest temperature the heat pump can still heat the house alone, and keep the furnace for capacity and outages. To check your own bill, multiply your price per gallon by 11.5 for your cost per million BTU through a 95% furnace. A heat pump at COP 2.5 wins above about 90¢ a gallon.

The furnace is a gas furnace converted with the manufacturer's propane kit by a qualified technician. Clark PUD pays $0 toward a heat pump in a propane-heated home, because its rebates require electric heat today, so the payoff comes from the fuel bill. If you heat with propane in rural Clark County, from Brush Prairie and Battle Ground out to Yacolt, we will price an all-electric heat pump next to the dual-fuel option.

The Clark County math for dual-fuel with natural gas.

On Clark PUD power, a cold-climate heat pump heats for less than a natural gas furnace down to about 5°F and keeps up at Vancouver's 22°F design temperature, so the two classic arguments for dual-fuel (gas is the cheaper heat when it is cold, and heat pumps lose capacity in the cold) are weak in Clark County.

Electricity vs gas cost at Clark County rates.

Clark Public Utilities usage rate (2026): 8.79¢/kWh. NW Natural usage rate: $1.506/therm. Fixed monthly charges are left out because they don't change with how you heat. A modern cold-climate heat pump at 25°F operates at roughly COP 2.5 (delivers 2.5 units of heat per unit of electricity). Math:

• 1 therm of gas = 100,000 BTU. At 95% AFUE furnace efficiency, delivered heat = 95,000 BTU. Cost: $1.506. Per million BTU delivered: $15.85.
• 1 kWh of electricity = 3,412 BTU. At COP 2.5 (heat pump at 25°F), delivered heat = 8,530 BTU per kWh. Cost: 8.79¢ per kWh, $10.30 per million BTU delivered.

At 25°F, the heat pump costs about a third less to run than the gas furnace. At 15°F, when the heat pump drops to COP 2.0, it is still about 19% cheaper ($12.88 vs $15.85 per million BTU). It stays cheaper until its efficiency falls below about 160% (COP 1.6), which for a modern cold-climate unit happens somewhere below 5°F, well under Vancouver's 22°F design temperature. On Puget Sound Energy or PGE power the math flips and gas usually costs less to run; see heat pump vs gas furnace in Seattle or Portland.

Heat pump capacity at PNW design temperatures.

Vancouver's heating design temperature is 22°F, the temperature the system is sized to keep up with. Mitsubishi Hyper-Heat multi-zone systems are rated for 100% heating capacity at 5°F with guaranteed operation down to -13°F, and American Standard low-profile cold climate heat pumps deliver 100% of their heat at 5°F and 70% of heating needs down to -13°F. At Vancouver's 22°F design temp, the system is working well within its capacity band, so a properly sized cold-climate heat pump keeps up on the coldest days of the year without backup.

When dual-fuel actually makes sense.

Dual-fuel makes sense in three cases:

1. You already have a working gas furnace that is not near end-of-life. The furnace cost is sunk. Adding a heat pump for shoulder-season heating and full-season cooling, with the furnace as deep-winter backup, is a smart capital move. These are usually called "add-on heat pump" installs.
2. You are concerned about ice-storm power outages. A gas furnace needs only a few hundred watts for its blower, inducer and igniter, so a small inverter generator can run it. A 3-ton cold-climate heat pump draws about 2,900 watts in mild weather and up to about 5,600 watts at 5°F, which takes a large portable or a standby generator. If grid reliability is a worry, dual-fuel with a backup generator covers more scenarios; see what size generator a furnace or heat pump needs.
3. You expect to be in the home short-term and the gas furnace is recent. If you bought a Vancouver home with a 5-year-old gas furnace and you plan to sell in 3–5 years, ripping out the working furnace makes less sense than adding a heat pump alongside it.

When all-electric is the right call.

For most new-construction homes, for homes with end-of-life furnaces, and for homeowners who plan to stay 10+ years, we recommend all-electric, for three reasons:

• Capital cost. Dual-fuel means buying and maintaining two systems. Going all-electric eliminates the furnace, gas line work, gas permit, combustion air requirements, and venting.
• Operating cost. At Clark PUD and NW Natural usage rates, a cold-climate heat pump heats for about a third less than a 95% gas furnace at 25°F.
• Maintenance simplicity. One system to service and one system to repair.

What we install for dual-fuel.

Pacific Peak's premium dual-fuel package:

• American Standard Platinum 20 heat pump (variable-speed, R-454B), outdoor
• American Standard Gold S9V2 96% AFUE gas furnace with variable-speed blower, indoor
• American Standard AccuLink Platinum thermostat with dual-fuel logic
• Outdoor temperature sensor for accurate balance-point switching

Installed cost: a dual-fuel system runs $11,300–$33,500 in Clark County at 2026 prices, depending on equipment tier, home size and electrical work.

We install both with equal care. If you are deciding between the two for your specific home, request a quote and we will run the actual numbers on both configurations and let you pick.

Questions homeowners ask.