Heat pump water heaters in cold climates

March 3, 2022 by Kevin Gries

Heat pump water heaters (HPWHs) can make a significant impact on decarbonizing water heating in residential buildings. However, the market has struggled to adopt HPWHs in cold climates such as the Midwest. This is probably due to two common misconceptions:

  • Heat pumps don’t perform well in cold climates
  • HPWHs have a cooling effect on the space around them, which would increase space heating in the home

Are either of these claims true? How do HPWHs actually perform in a cold climate?

Testing HPWH performance in the field

Slipstream recently conducted a robust monitoring study on heat pump water heaters for MECA, in which we studied the latest generation of HPWHs in the cold climate of the upper Midwest. The project included a field study of HPWH performance in nine homes in rural or village settings.

At each site, we installed monitoring equipment to measure HPWHs' impacts on performance, cost, and space heating compared to electric resistance, propane-fired, and natural gas-fired water heaters. In addition to the monitoring data, we conducted a survey of 81 households that have installed HPWHs to gain insights on how people felt about the technology in their homes.

Findings from the study

Programs should account for the actual efficiency. The energy factor we derived in the field was roughly 65–75% of the manufacturers' efficiency ratings. Keep this in mind as you consider heat pump water heaters in energy efficiency or decarbonization plans.

Cost savings are greater when replacing electric resistance or propane-fired water heaters. Replacing these appliances with HPWHs resulted in the most attractive paybacks and operational cost savings. While HPWHs may have a lower operational cost in some localities than natural gas water heaters, the savings are likely smaller than the cost difference of the appliances.

Make sure installers and residents know how to set the controls. Appropriate control settings are important to optimize the performance of HPWHs.

Customer satisfaction wasn't an issue in our study. Our monitored installations were all in basements of single-family homes, and we couldn't detect an increase in space heating from using a heat pump water heater. Residents rarely complained about the HPWH affecting their comfort in their home. In fact, overall, our survey respondents reported high satisfaction with the technology.