A novel dual tank solar-assisted heat pump (SAHP) system configuration for domestic hot water heating was developed. Due to the multiple modes of operation arising from the configuration, it was necessary to develop a custom control strategy to minimize electricity consumption. The controller evaluates which modes of operation are possible given the current conditions and selects the best mode from those available. The system modes of operation were validated experimentally,using a test apparatus built at the University of Waterloo. Annual simulations of system performance for a single-family residential home indicate that the dual tank SAHP system developed provides significant energy savings in comparison to a traditional solar domestic hot water system. Using a benchmark comparison of a standard electric domestic hot water system and a solar domestic hot water system, the dual tank SAHP increased energy savings from 60% to 69% for 7.5 m(2) solar collector area. Applying the system to a larger load offers the potential for significant energy and cost savings, which would improve economic justifiability. (C) 2015 Elsevier Ltd. All rights reserved.