The Building Science Education Solution Center (BSESC) website is a valuable source of training tools and information on heat pump water heaters (HPWHs). However, for those seeking further knowledge and additional information on HPWHs, a selection of external resources is listed. The inclusion of any external resource in the list does not imply a preference or endorsement by PNNL. The list is provided solely for the purpose of offering additional options for continued learning and supplemental information on HPWHs. Users are encouraged to explore these resources at their own discretion and in no particular order.