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Water heating is now the second largest residential energy user, with space heating being the largest. More than 40% of U.S. households provide domestic hot water using electric resistance storage water heaters. A significant opportunity exists to improve water-heating energy efficiency in these households through the use of heat pump water heaters (HPWHs), which offer potential energy savings of 50% or more. Unlike electric resistance water heaters, HPWHs function much like a refrigerator in reverse. Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. This process makes them two to three times more energy efficient than standard electric resistance water heaters and can cut water heating costs by up to 60%.

For domestic hot water needs in multifamily buildings, there are two HWPH applications: (1) unitary in-unit water heaters, or (2) central water heaters, serving multiple apartment units. Here are key considerations when deciding if HPWHs are the right solution for your multifamily building:

  • Space – Heat pump water heaters typically require at least 700cubic feet of air-flow around them. This is equivalent to 8’x9’x10’ of space. Air-flow requirements vary by product, and some units can be installed in much less space if you employ ducting or other air-flow strategies.
  • Sound – Heat pump water heaters generate sounds similar to the background noise from a portable fan (around 45 decibels). When installed in a separate living space, very few occupants are aware they are operating.
  • Cool air – While in operation, heat pump water heaters release cool, dry air into the surrounding space.
  • Size/height – Heat pump water heaters may be slightly larger than standard electric water heaters.

Learn more about heat pump water heaters at www.hotwatersolutionsnw.org

When heat pump water heaters are coupled with low flow plumbing fixtures, such as faucets and showerhead, the savings for both energy and water can be tremendous. The Multifamily Energy Program’s Existing Building – DHW Bundle and New Construction – DHW Bundle promotes the installation of heat pump water heaters, and low flow faucets and showerheads. Learn more about these program bundles in the Program Manual.