The role of backup fuel in residential electrification: assessing the environmental, economic, and grid impacts of heat pump backup systems in cold-climate residential

Electrifying residential heating using heat pumps is critical for decarbonization. However, during extreme low temperatures heat pumps typically require backup. Backup fuel choice can have significant impact on emissions, cost, and peak electricity demand. This study employs an hourly techno-economic model to simulate space heating and cooling energy demand for a nationally representative sample of 6,000 Canadian homes and compare the impacts of adopting heat pumps with either electric or natural gas backup versus new conventional furnaces. We analyze space heating and cooling energy consumption, GHG emissions, household economics, marginal abatement costs, and electricity demand profiles. Results show that fully electrified heating systems can cut annual space heating and cooling energy use by over 59% and reduce national residential emissions by up to 21 Mt CO₂e/yr compared to new conventional furnace replacements. However, only 9% of households save money by adopting fully electric heating systems in the absence of supportive policy, and these systems increase peak electricity demand. Hybrid gas-backup systems have smaller impacts on peak electricity demand and on greenhouse gas reduction.