It Sounded Good on Paper: Field Performance of Residential Heat Pumps in the Pacific Northwest

Bob Davis, David Baylon, and Shelly Strand, Ecotope, Inc.

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Abstract

Air-source heat pumps have been touted as energy conservation measures in the Pacific Northwest for at least two decades, and many regional utilities have subsidized their installation. However, no comprehensive study of heat pump installations has been done and several regional actors, including the Bonneville Power Administration, electric utilities, and State Energy Offices, have long been interested in the assumptions that underpin energy savings estimates, especially assumptions regarding system sizing (“tons”) and control of auxiliary (electric resistance) heat. A total of 160 regional heat pump installations were evaluated in this project as part of a larger study that included a billing analysis and heat pump bench testing. The field evaluation utilized a detailed protocol and included a review of system controls, evaluation of duct system performance, evaluation of system airflow and refrigerant charge, and estimation of building shell heating load and its relationship to heat pump capacity. Results from this work were used to revise estimates of regional heat pump energy usage and to inform ongoing efforts to improve field installation protocols that are required as prerequisites to receive utility incentives.