SOL Perpetua System
How the Sol-Perpetua System Works
6. HOT WATER TANK
The storage tank is usually a standard tank with electric immersion heaters. We recommend a 364 litre (96 US gallon) tank for a family of four or two smaller tanks connected in parallel. By disconnecting the upper heater or putting it at a low setting, the lower two thirds of the tank(s) will be available to receive solar heat while the upper third will always be hot; the upper heater can be switched to come on when there is not enough sunshine to meet the demand for hot water.
If you are blessed with reliable sunshine for long periods of time you will save electricity by switching it off altogether.
Storage tanks are usually not insulated as much as is desirable. An extra wrap around insulation blanket is recommended.
If your back-up water heating is by means of a gas fired hot water tank, you will need another tank to accept heat from the solar collector panels. The sun's energy then preheats the cold water before it enters the gas fired hot water tank.