Using a Hitachi evacuated tube solar collector, 1.7 m2, to preheat hot water.
This South West facing panel may collect 1500kWh per year when pre-heating water.
The 100 litre cylinder provides a solar storage volume of approximately 60 litres per m2 of panel.
When the water in the solar panel is 4o hotter than the water in the tank a 40W pump is switched on by a differential temperature sensor to transfer the heat.