A New Testing Procedure

Jun 22, 2020

As variable capacity heat pumps become more popular, consumers and their contractors need an accurate rating system to evaluate the energy efficiency of various models. Current HSPF and SEER heating and cooling ratings do not accurately evaluate the efficiency of variable capacity heat pumps. For example, the Air-Conditioning, Heating, & Refrigeration Institute (AHRI) test procedure takes place at maximum output under a single operating condition. Because variable capacity heat pumps perform better at mild outdoor temperatures and have more advanced controls, the industry needs a test procedure that adjusts to measure the demands on the heat pump as the outdoor temperature gets warmer and colder. This type of test procedure, referred to as “load-based,” can more accurately judge the performance of a heat pump, especially equipment with advanced controls.

Developing a New Testing Procedure

Major laboratories, utilities, and energy efficiency organizations from across North America helped design a new voluntary test procedure and rating to better showcase the performance of these heat pumps and their controls. Manufacturers have also been invited to contribute and several are also involved to help improve the new test procedure. The new procedure (CSA EXP07) is currently under technical review. The group will likely publish a final version in 2021. The test procedure showcases a full performance heat pump “map” across a variety of heating and cooling conditions. This performance map informs a set of seasonal COP ratings for both heating and cooling in eight different North American climate zones.

This test procedure will likely not replace the current HSPF or SEER ratings, but it will provide additional information for contractors and utilities. Contractors can use the test procedure findings to make better equipment selections and sizing decisions. Utilities can use the findings to identify top-performing variable capacity heat pumps for their customers.

Early results of this new test procedure have already shown that not all heat pumps perform the same, even if they have the same HSPF or SEER ratings. The big discovery so far is just how important the heat pump’s controls strategy is for handling defrost cycles, adjusting to changes in thermostat use, and operating under mild outdoor conditions. For example, the new test procedure evaluated four heat pumps with the same HSPF rating (12.0) under close to real world conditions. The test found the worst performing unit used twice as much energy as the best performing unit. This difference in energy performance makes it hard for both utility programs and their customers to rely on current HSPF and SEER ratings to deliver real savings and support heat pump incentives.

Next Steps

The next step on the path to better performance data is to evaluate the new test procedure’s repeatability (test-to-test accuracy), reproducibility (lab-to-lab comparison), and representativeness (how well the tests compare to in-field performance). While the current AHRI test is repeatable and reproducible, the results are not very representative of real-world performance.

The new test procedure group is working together to review the new testing standards and develop a database of tested equipment. The group will continue working through 2021-2022 and aims to share real results with utilities and HVAC contractors by 2023. Natural Resources Canada has publicly stated that they would like to see all heat pumps sold in Canada rated using this type of test procedure by 2025. The California Energy Commission is also building the rating into future versions of energy code compliance software.

The NW Ductless Heat Pump Project will continue to keep utilities, distributors and contractors informed about this new procedure and results.