Hybrid Dual-Fuel Heating: Heat Pump Plus Furnace

Hybrid dual-fuel heating combines an air-source heat pump with a furnace. The heat pump handles mild and moderately cold weather. When the outdoor temperature drops below a set switchover point, the furnace takes over. One smart thermostat or control board decides which runs.

For many Canadian homes with a gas or propane furnace, a dual-fuel setup is a practical middle path. You get efficient heat and summer cooling from the heat pump, and the furnace covers the coldest nights without relying on electric resistance backup.

How hybrid dual-fuel heating works

The heat pump's outdoor unit sits where your AC condenser would go. Its indoor coil sits on top of your furnace, sharing the same ducts and blower. Only one heat source runs at a time.

• Above the switchover temperature: the heat pump heats your home.
• Below it: the heat pump shuts off and the furnace runs.
• In summer: the heat pump runs in reverse as your air conditioner.

Choosing the switchover temperature

There are three common ways to set the switchover point. Your installer can program any of them.

Economic balance point

This is the outdoor temperature where the heat pump and furnace cost the same per unit of heat. Above it, the heat pump is cheaper. Below it, the furnace is cheaper. To find the break-even COP, divide your electricity price by your gas cost per kWh of heat. With a 95% furnace, each m³ of gas delivers about 9.83 kWh of heat.

A typical cold-climate heat pump runs at a COP of about 3 to 4 around 5 °C and about 2 near -15 °C. Compare those with the break-even figure for your province. Check the COP chart for your specific model, since it varies a lot.

Thermal balance point

This is the temperature where the heat pump can no longer keep up with your home's heat loss. Below it, the house would cool down without help. A good installer calculates this from your heat loss and the unit's capacity chart. In a well-insulated home with a cold-climate unit, it may be -20 °C or lower.

Emissions or comfort

Some homeowners set the switchover as low as the heat pump allows to cut emissions, accepting a slightly higher bill. Others prefer the furnace in deep cold because the air from the vents feels warmer.

Who dual-fuel heating suits

• Homes with a gas furnace under about 10 years old. You keep a working furnace and add the heat pump when your AC needs replacing.
• Homes in cold regions where a heat pump alone would need a large backup.
• Ontario and Manitoba homes, where gas is cheaper in deep cold but a heat pump can win in milder weather.
• Propane-heated homes, where propane at about $0.90/L costs about $134 per 1,000 kWh of heat from a 95% furnace. A heat pump is usually cheaper for most of the season.

Who it does not suit as well

• Quebec, BC and Atlantic homes, where a heat pump is cheaper in nearly all weather. A full heat pump with electric backup may make more sense. Compare in our heat pump vs gas furnace guide.
• Homes with a furnace near the end of its life. Replacing it just to keep a backup adds cost. See our furnace replacement guide.
• Alberta and Saskatchewan homes chasing savings alone. At current prices, the heat pump mainly adds cooling and lower emissions.

Costs and trade-offs

Adding a heat pump to an existing furnace usually costs a bit more than a new central AC, since the outdoor unit and coil are similar. You keep paying your gas utility's monthly fixed charge, which a full electric conversion would remove. Ask whether your province's rebate program covers heat pumps installed with a furnace backup, since rules differ. Our rebates page lists current programs.

To see how a hybrid setup compares for your home, enter your gas use in the heat pump calculator. If you want to understand how heat pumps behave in deep cold, read is a heat pump worth it in a Canadian winter.