Tech Evaluation of Air-to-Water Heat Pumps

This report provides results from a market assessment and pilot study of efficient residential air-to-water heat pump technologies with load-shift capabilities through coupled thermal energy storage and supplemental air-source heat pump cooling. Results quantify the energy and cost savings, cost effectiveness, and emission reduction potential of shifting space heating loads to off-peak times, an essential strategy to alleviate grid constraints as more homes in California electrify their end uses. The market assessment is informed by a literature review of the available technologies and components, as well as publicly available results from studies conducted on packaging and controls technologies, system performance models and field testing of storage systems integrated with heating, cooling and domestic hot water heating. Development of the pilot study stemmed from the market assessment results and data gaps identified in the market. The team recruited four single family households in California to participate in a field testing of the technology during typical household operation. A commercially available heating and hot water system consisting of an air-to-water heat pump with integrated thermal energy storage, supplemented with an air-source heat pump for cooling and supplemental heating was installed in each home. Data were collected while the system operated in both a baseline mode and load-shift mode to understand differences in energy use and to compare costs based on utility time-of-use rates for peak, partial peak and off-peak times.