Can heat-pumps provide routes to decarbonization of building thermal control in the US Midwest?

Climate change mitigation demands rapid decarbonization; in cold regions such as the US Midwest, building thermal control (BTC) presents a potential for significant cuts in emissions by combining renewable energy with heat pumps. Trends in natural gas and electricity pricing over the period 2007-2020 have significantly upended economic feasibility of this decarbonization approach. Heat pump-based BTC has moved from being cost advantageous in operations but higher GHG emitting (in 2007), to the exact opposite-higher cost but lower emitting (in 2020). Due to energy price fluctuations, the coefficient of performance required of a heat pump to breakeven on operational cost with high efficiency natural gas heating has doubled, changing from 2.25 to 4.5 over the period 2007-2019. The value of 4.5 is infeasible for all available cold-climate heat pump systems. Thus, while electrification via both air-source and ground-source heat pumps is a commonly identified component of decarbonization plans in the region, actual implementation has declined. Improvements in heat pump performance, overcoming adoption barriers, and adopting policies that buffer long-term climate solutions against short-term price fluctuations are all needed. In part due to continuing decreases in carbon intensity of electricity, heat pump climate benefits can be substantial over project life cycles; however, there is no current policy mechanism to enable this benefit to be considered relative to short-run economic considerations.