Water-source heat pumps (WSHPs), which are generally used in commercial buildings, are installed as part of a system where multiple heat pumps are connected to a common water loop. In heating mode, the heat pump transfers heat from the water loop to a space, while in cooling mode, the heat pump transfers heat from the space to the water loop. Water-source heat pump systems allow for moving heat from one area of a building to another during times when some spaces need cooling while others require heating. Water-source heat pump systems typically also include a boiler and cooling tower for times when it is necessary to add additional heat to the water loop or reject heat from the loop.
In 2015, DOE adopted the efficiency levels for WSHPs in the 2013 version of ASHRAE 90.1 as new national minimum standards. ASHRAE 90.1 is a commercial building energy code. The Energy Policy and Conservation Act (EPCA) requires that if the equipment efficiency levels in ASHRAE 90.1 are amended, DOE must either establish amended standards for the products at the levels specified in ASHRAE 90.1 or establish more stringent standards if they would result in significant additional energy savings and are technologically feasible and economically justified. The new standards took effect in October 2015 and represent energy savings of about 8% relative to the previous standards.
Technology options for improving the efficiency of water-source heat pumps include higher-efficiency compressors and fan motors.