This white paper examines efficiency metrics (ratings) for residential and small commercial heat pumps and explores the potential benefits and impacts of improving those metrics. It presents evidence that existing metrics are not reliable, particularly for modern, variable-speed heat pumps and air conditioners that are expected to be more efficient, but don’t always live up to their ratings. Moreover, these systems’ built-in firmware—the internally programmed set of operating instructions—can have a significant impact on real-world performance, yet the firmware operation is explicitly excluded from current rating procedures. This paper presents the case that a much better rating metric would utilize a load-based testing procedure that fully characterizes heat pump performance under realistic operating conditions, including the systems’ built-in firmware.
A non-technical companion document provides a visual illustration of the concepts behind “why metrics matter” for utilities and efficiency programs by distilling the white paper’s key concepts with engaging graphics.