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Putting the Heat on Reducing Energy Costs

January 2015

Americans are constantly looking for ways to save money on their utility bills. Today, there is another opportunity with an alternative water heater—the heat pump water heater. Researchers in PNNL's Energy Policy and Economics group estimate that replacing traditional electric water heaters with heat pump water heaters can decrease energy use by as much as 63 percent, as long as proper ducting is part of the equation.

Exactly what is proper ducting? Ducts are basically tubes that allow for airflow to and from the heat pump. Partially ducting a heat pump consists of an exhaust-only duct that draws air out of the home to the outdoors. A fully ducted heat pump would not only exhaust air, but collect outdoor air as well. So which method works better?

With funding from DOE’s Office of Energy Efficiency and Renewable Energy and the Bonneville Power Administration, researchers tested the heat pump water heaters at PNNL's Lab Homes. Various duct configurations were tested, including no ducting, partial ducting, and full ducting. Data showed that the home with the fully ducted heat pump water heater used 4.2 percent less energy than the home with no ducts. This would lead to a 10-year cost savings of nearly $2,000 for the 1,500 square foot home. The team found that the partial, exhaust-only, ducting actually increased energy use by 2.9 percent.

The PNNL research team continues to evaluate heat pump water heaters and plans to perform studies in differing climates and homes. Data and lessons learned from additional field tests will allow them to establish best practices for heat pump water heater installation. To learn more about their research, read the PNNL news release.


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