Air-to-Water Heat Pump Field Study

This research project will assess air-to-water heat pump (AWHP) retrofits in existing and new construction residential single family and multifamily buildings in Wisconsin. The first phase of the project will consist of identifying buildings, sourcing bids on system design, and modeling energy savings. The second phase of the project will consist of installation and monitoring of the AWHP systems which will be used to develop a workpaper for future offerings. Comprehensive findings from the research will be shared in a final report.

Researcher: Slipstream

Timeline: October 2023 – September 2025

Sector: Residential

About the Research Study

An air-to-water heat pump is an electric heating system that pulls heat from the outside air and transfers it to the water pipes that deliver heat to radiators and in-floor radiant systems, doing the work of a boiler or geothermal system. They can operate at up to 500% efficiency and can work in tandem with a backup boiler, saving substantial amounts of energy and potentially reducing energy costs. Air-to-water heat pump systems have been used in Europe for years and are already gaining traction in the Northeast of the U.S.

This research is currently in the outreach phase and looking for owners of single-family homes or multifamily properties in Wisconsin to participate in our study of this next-generation air-to-water heat pump technology, ready to perform in cold Midwest winters.

Why Participate?

Take the opportunity to heat your home with one of the first air-to-water heat pump systems deployed in Wisconsin, paid for in full by Focus on Energy. You will play a crucial role in this field study by giving feedback on your satisfaction with the system and allowing Focus on Energy to monitor the system as it heats your home. By participating, you contribute to advancing the understanding of air-to-water heat pump technology and its applications in Wisconsin’s colder climates.


New Construction


Full cost with installation up to $35,000, paid to the homeowner

$10,000, paid to the builder


Full cost of design and installation up to $100,000, paid to the building owner


How to Participate

If you are single-family homeowner interested in participating, please complete the pre-screening questionnaire to see if your home qualifies. A team member will reach out to you after you complete the survey.

If you are a builder or installer that is interested in participating in the study, please contact Cynthia Segura at

Participating homeowner obligations:

  • Complete a pre-installation survey to characterize existing equipment and household characteristics.
  • Allow Focus on Energy staff to conduct an in-person or virtual walkthrough to verify the air-to-water heat pump will work well in your home.
  • Sign a participation agreement with Focus on Energy.
  • Allow Focus on Energy to add an air-to-water heat pump to your existing heating distribution system, and potentially make other changes such as replacing radiators.
  • Allow Focus on Energy to install monitoring equipment to measure and verify the performance of the water heater for a 6 to 12 month period after the equipment is operational. Monitoring equipment will be removed after the study.
  • Share your experience with the equipment through quarterly check-ins and a closing interview.
Participating sites and customers must meet the following criteria:
  • Participant must own the single-family or multifamily building where the heat pump is being installed.
  • The building site must receive electricity from a participating Focus on Energy utility.

For either single-family or multifamily retrofit sites, the following are eligibility requirements:

  • 75% or more of the heating load is currently delivered by a natural gas or electric boiler.
  • A hydronic space heating distribution system capable of delivering sufficient heat from low temperature (<130⁰F) water, which will be either of:
    • An in-floor radiant heating system.
    • A radiator system in a building that has seen substantial envelope improvement from weatherization.
    • A radiator system in a building where rooms have sufficient space to upsize the radiators.
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