Heat Pump Water Heaters (HPWHs) are a promising technology for energy-efficient residential water heating. HPWHs use heat pump technology to heat water more efficiently than electric resistance and gas- or propane-fired water heaters. However, traditional HPWHs require a dedicated 240V circuit, reducing their cost-effectiveness as an electrification solution if major electrical upgrades are necessary. To address this, manufacturers released 120V HPWH models that plug into a standard wall outlet. These units avoid electrical upgrades, but heat water more slowly.
The first phase of this research (2022) was comprised of market research and modeling of the potential for 120V HPWHs in Midwest homes. The study found that 120V HPWHs can provide sufficient hot water for residents with typical hot water usage. However, interviews with plumbers, distributors, and retailers indicated they would be unlikely to sell the product without validation of 120V HPWHs’ high performance in cold climates.
In the second phase of this research (2024), Focus on Energy conducted a field study in Wisconsin in partnership with utilities in other Midwestern states to assess cold climate performance for 120V HPWHs. The field study outlined market potential and savings opportunities of 120V HPWHs in Wisconsin by evaluating the performance of the units in real homes. The field study final report provides recommendations for programs on the best applications of 120V HPWH units, unit installation guidelines and best practices, interview and survey results from installers and consumers, and quantitative analyses of unit effectiveness and efficiency.
As of March 2025, 120V HPWHs are not yet available in the Midwest. However, this research project demonstrated that 120V HPWHs are feasible in Wisconsin climate zones and will provide benefits to utility customers. As a result of the research, manufacturers have stated that they will evaluate deployment of these models into the Midwest.
Timeline: May 2022 - December 2024
Customer Segment: Single-family residential
Demonstration Project Objectives
In the first phase of the project, the research team completed market research and modeled 120V HPWH performance under several water usage patterns. Results from this phase of the project included the following:
In the second and most recent phase of the project, the research team installed and monitored 120V HPWHs in 27 single-family Midwestern homes. Results and recommendations from this phase of the project included the following:
Additional conclusions and recommendations regarding installation best practices, unit availability, water consumption and runouts, energy use and efficiency, and retrofit and operating costs can be found in the Phase 2 Final Report linked below.
In the first phase of this project, the research team conducted energy modeling, cost analysis, secondary data analysis, and supply chain research to determine the best applications for 120V HPWHs in Wisconsin. Results from this phase of the project can be found in the Phase 1 Final Report below.
Research and Modeling Report: 120V HPWH Phase 2 Final Report
Field Study Report: 120V HPWH Phase 1 Final Report
For more information about this study, email FutureFocus@Focusonenergy.com.