Three different storage tanks that comprise the NZERTF’s domestic hot water system. Starting from the left – the first tank is a nominal 120 gallon tank that is connected to the solar thermal collectors through the use of a heat exchanger; the second tank is a nominal 80 gallon tank that can also be connected to the solar thermal collectors; the third tank (furthest to the right) is the heat pump water heater. The two storage tanks associated with the solar thermal system were installed to give the researchers flexibility in selecting various collector to storage size ratios for research. This system may also be used for a future combined geothermal solar thermal heating system.