The Federal Government Clean Energy Regulator specifies the thermostat range of all iStore style compressor hot water systems, the thermostat range is 12 degrees, this means that the bottom of the tank must fall 12 degrees below the target temperature before the heating cycle begins. The hot water delivered to the house is from the top of the tank as natural convection causes the hot water to rise to the top of the tank all of the hot water is available for use.

The iStore has one large tank and two temperature sensors in the tank, bottom and top, the larger temperature is in the centre of the LCD and this is the water temperature at the top of the tank. Water is delivered from the top of the tank and therefor is the delivery temperature. The smaller temperature in the top left is the water temperature towards the bottom of the tank and is used to control the heating cycle.