California Energy Commission staff completed modeling bill impact analysis to estimate the energy and cost impacts to residents with low-income qualified energy utility rates of retrofitting existing homes in California. This report describes the method and results of using California Building Energy Code Compliance software. This analysis seeks to estimate, comparatively, where in California certain decarbonization measures will provide energy bill benefits to residents and where greenhouse gas emission reduction benefits can be maximized.
The baseline existing home prototypes are modeled with gas end uses for domestic hot water, space heating, cooking, and clothes drying. The decarbonization measures included in this analysis are heat pump water heaters, heat pumps for space conditioning, electric cooking, and electric clothes drying. The weatherization measures include, in a subset of the residential building prototypes, attic insulation, floor insulation, duct sealing, air sealing, and solar window films.
Bill impacts are calculated by comparing the energy bill of each retrofit to the energy bill of the baseline, in each of the 16 climate zones. Utility rates, up to December 2024, for Pacific Gas and Electric, Southern California Edison, San Diego Gas & Electric, Southern California Gas Company, Los Angeles Department of Water and Power, and Sacramento Municipal Utility District are included in this analysis.
Results show that each climate zone has decarbonization retrofit measure combinations and rates that lead to energy bill savings. High energy bill savings are achieved with space-cooling efficiencies in high-cooling-load climate zones. Low energy bill savings and, in some cases, bill increases occur in climate zones with low cooling load and high heating load. Results also show that electricity rates with low volumetric charges are most electrification-friendly, leading to higher energy bill savings. Additionally, while replacing any gas fired appliance with an electric appliance will reduce greenhouse gas emissions, the most impactful decarbonization measures across all climate zones is changing from a gas water heater or furnace to electric heat pump technology. As a next step, staff plans to use interval meter data to calibrate the modeled results of energy consumption and utility bills to improve accuracy and better identify appropriate retrofit measures.
