This paper explores the year-long performance of a 189 L (50 gal) heat pump water heater (HPWH) serving as an auxiliary unit to an active, indirect solar thermal water heater with a 303 L (80 gal) storage tank in a net-zero energy test home located in Gaithersburg, MD.

Prepared by:  National Institute of Standards and Technology

Published:  January 2016