Field Performance of Inverter-Driven Heat Pumps in Cold Climates

Timothy Merrigan, James Williamson, Robb Aldrich, Stacey Rothgeb (NREL Technical Monitor)

Research output: NRELSubcontract Report


New inverter-driven ASHPs are gaining ground in colder climates. These systems operate at sub-zero temperatures without the use of electric resistance backup. There are still uncertainties, however, about cold-climate capacity and efficiency in cold weather and questions such as coil. CARB observed a wide range of operating efficiencies and outputs from site to site. Maximum capacities were found to be generally in line with manufacturer's claims as outdoor temperatures fell to -10 degrees F. The reasons for the wide range in heating performance likely include: low indoor air flow rates, poor placement of outdoor units, relatively high return air temperatures, thermostat set back, integration with existing heating systems, and occupants limiting indoor fan speed. Even with lower efficiencies than published in other studies, most of the heat pumps here still provide heat at lower cost than oil, propane, or certainly electric resistance systems.
Original languageAmerican English
Number of pages48
StatePublished - 2015

Bibliographical note

Work performed by Consortium for Advanced Residential Buildings (CARB), Norwalk, Connecticut

NREL Publication Number

  • NREL/SR-5500-63913

Other Report Number

  • DOE/GO-102015-4642


  • air flow measurement
  • air source heat pumps
  • ASHP
  • Building America
  • cold climate
  • consortium for advanced residential buildings
  • COPs
  • heat pump
  • heating
  • inverter-driven
  • Northeast
  • performance
  • residential
  • residential buildings
  • Steven Winter Associates, Inc.
  • SWA


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