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Electrification with heat pumps is often cited as a preferred pathway to decarbonize US space heating in the transition to a net-zero energy system. However, fully electrifying building heat may significantly increase peak electric system loads during cold weather, thus challenging extensive adoption. A hybrid home heating system uses both heat pumps and conventional natural gas furnaces, where the gas appliance operates during peak heating periods. Here, we assess the marginal abatement costs of fully electrifying peak heating demands as opposed to allowing hybrid heating in current gas connected and ducted homes. We use a least-cost energy system optimization model that considers household, electric, and gas system costs, including electric distribution system expansion and gas system cost recovery. To ensure the cost of sufficient low-carbon dispatchable electric capacity is captured, the model includes historical days with peak heating demands and low wind and solar availability. We find hybrid heat pumps can achieve substantial decarbonization, with US natural gas residential heating consumption decreasing 70% to 95% from 2020 levels at marginal abatement costs below $200 per tonne CO _2 e. The cost of fully electrifying heating in cold regions is very high, with the marginal abatement cost of eliminating the last 1% of natural gas consumption exceeding $1000 per tonne CO _2 e even in scenarios designed to be favorable to electrification. The robust value of hybrid heat pumps in northern cold climates indicates the importance of flexible building heat decarbonization policies such as clean heat standards.

Projections of increased domestic natural gas supply and low prices have encouraged increased natural gas utilization in the United States electricity sector. Natural gas can offset coal, likely decreasing overall greenhouse gas (GHG) emissions and other air emissions such as SO _2 and NO _X . Previous life cycle assessment (LCA) studies using limited system boundaries have attempted to quantify the benefit of offsetting coal use. However, these studies do not consider that relative regional fuel prices may contribute most to the choice of coal over natural gas. External incentives such as low natural gas prices compared to coal are required if natural gas is to displace coal. In this study, simplified economic dispatch models are used to determine how natural gas utilization will increase in the short-term in response to changes in natural gas prices in three US grid regions—ERCOT, MISO and PJM. The results indicate that the change in air emissions is lower than suggested by LCAs, since LCAs generally do not include the complexity of regional electricity grids. For instance, this study estimates that life cycle GHG emissions may, at best, decrease by 7–15% due to low natural gas prices, compared to almost 50% reductions estimated by previous LCAs.