Assumptions used in the California heat pump analysis

The document details the baseline and new system efficiencies for air source heat pumps (ASHP) and heat pump water heaters (HPWH), the use of NREL ResStock for hourly energy load profiles, and the specific utility rates for electricity, natural gas, and propane applied across California's climate zones.

• The analysis assumes specific efficiency ratings for current and new systems: current gas/propane furnaces are rated at 85% AFUE and current AC at 13 SEER2, while new ASHPs are rated at 16 SEER2 with HSPF2 ratings of 8 (IECC climates 2-4) or 9 (IECC climates 5-6). New heat pump water heaters (HPWH) are assumed to have a 3.7 UEF and 330% effective efficiency in hybrid mode, compared to current gas/propane water heaters at 0.70 UEF.
• Hourly energy load profiles for typical single-family homes were sourced from the National Renewable Energy Laboratory’s (NREL) ResStock. For cold climate heat pumps in IECC climates 5 and 6, performance was based on an average subset of 100 common ASHPs from the Northeast Energy Efficiency Partnerships’ database, with electric resistance heating covering any unmet load.
• The analysis utilizes specific energy rates, including a national-average propane rate of $2.51/gallon and weighted average natural gas rates for SCG, PG&E, and SDG&E. Electricity rates are sourced from Arcadia’s Signal database, with different rate plans applied for 'Pre ASHP or HPWH' and 'Post ASHP or HPWH' scenarios across various utilities including SCE, PG&E, SDG&E, LADWP, SMUD, and Imperial Residential.

APA

RMI (n.d.). Assumptions used in the California heat pump analysis. https://rmi.org/wp-content/uploads/2025/04/Assumptions-used-in-the-California-heat-pump-analysis.pdf

Chicago

RMI. Assumptions used in the California heat pump analysis. n.d. https://rmi.org/wp-content/uploads/2025/04/Assumptions-used-in-the-California-heat-pump-analysis.pdf.

Wikipedia

{{cite report |author=RMI |title=Assumptions used in the California heat pump analysis |url=https://rmi.org/wp-content/uploads/2025/04/Assumptions-used-in-the-California-heat-pump-analysis.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{rmindassumptions, author = {{RMI}}, title = {{Assumptions used in the California heat pump analysis}}, institution = {RMI}, url = {https://rmi.org/wp-content/uploads/2025/04/Assumptions-used-in-the-California-heat-pump-analysis.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }