A long-term reliability test of an integral-type solar-assisted heat pump water heater (ISAHP) was carried out. The prototype has been running continuously for more than 13,000 h with total running time >20,000 h during the past 5 yr. The measured energy consumption is 0.019 kWh/1 of hot water at 57 degreesC that is much less than the backup electric energy consumption of the conventional solar water heater. (C) 2003 Elsevier Ltd. All rights reserved.