Heat pump vs furnace vs boiler

Three machines

A heat pump is an electrically driven device that takes heat from a colder place and delivers it to a warmer one. The refrigerant absorbs heat outdoors, the compressor raises its temperature, and the indoor coil gives that heat to the house. Reverse the flow and it cools. NRCan Because it moves heat, its coefficient of performance is above 1 in its operating range: more heat out than electricity in. As outdoor temperature drops, there is less heat to take, capacity falls, and COP falls with it.

A furnace burns oil, propane, or wood pellets (or heats air with electric elements) and blows warm air through ducts. A boiler does the same combustion and sends hot water to radiators or in-floor tubing. Combustion efficiency is an AFUE or a steady-state number below 100 percent of the fuel’s energy. It does not collapse at −40°C the way an air-source heat pump’s capacity does. The fuel still has to be there, and the flame does not care what the electricity grid is doing.

What that means at design temperature

NRCan’s guide is explicit that below the thermal balance point the heat pump covers only part of the load and supplementary heat is required, and that many air-source units simply stop somewhere between about −15°C and −25°C. A hybrid arrangement — heat pump plus furnace or boiler — is one of the setups NRCan describes. NRCan The Arctic Energy Alliance’s Yellowknife monitoring note, published June 11, 2026, says the same thing in local weather: the cold-climate units ran, and a furnace or boiler was still required in extreme cold. AEA

Yukon’s rebate terms pick the hybrid on purpose. The heat pump is the efficient machine for the large number of hours that are cold but not design-cold. The furnace, boiler, or stove is the machine for the design day and the outage. Replacing a furnace with a heat pump and no backup is a different design, and it is not the design the dual-fuel rebate pays for.