A Brief Discussion on The Basics of Converting Your Geyser to Solar Water Heating
Heating water is often the single biggest consumer of electricity in your home. When considering going off-grid, heating water is thus a major consideration. It would be best to find some way of reducing the amount of electrical energy used to heat water before you consider installing expensive alternative power such as solar PV panels, because that will significantly reduce your daily electrical energy consumption requirements and thus significantly reduce the size and cost of the alternative power system needed. To estimate how much energy your electric geyser uses per day try using the OffGridDiy calculator.
One relatively cost effective way of heating water is to convert your existing geyser to a direct solar water heating system. A direct solar water heating system will typically reduce the amount of electrical energy spent heating water by about 50% on average over the year.
The article at OffGridDIY.co.za provides a brief overview of of how to go about that.