Current solar systems both water heating and current generating systems are very inefficient.
The solar water heaters on the roof generate lots of hot water during the day when nobody is using it. Most people take a bath or shower in the evening or early morning. If its taken in the morning then all that hot water that was generated the previous day was a waste because the mains electric element would have to be activated to keep the water hot during the night for the next morning. If you use the hot water for washing in the evenings then you will use the solar hot water that was generated provided that everyone washes in a limited time frame because cold water will be added to the hot water tank as the hot water gets used and when that happens the mains electrical element will come on to heat up the water again. So you can see the amount of saving on your electrical bill with these solar water products are limited.
Electrical current solar systems are too expensive and inefficient. Most small units vary in price from R50, 000 to a R100, 000 with limited solar capabilities. Even for a small system they use massive solar panels just to discard most of that power via a regulator when the batteries are fully charged. The solar panels available are all 12V DC so are most of the batteries for them. All current solar systems convert this low voltage battery power in to 220V AC via a very inefficient inverter that requires huge amounts of input power and only give out a small output power. A small R100.000 solar system is sold, as a product to save on a electric bill it cannot replace the mains power. These inverter systems are not capable of heating a geyser or running an electric stove .Its only capable of running things like fridges, TVís and sound equipment that are not big consumers of electricity.
I donít believe in using regulators and inverters when I buy an 80W solar panel I want to use that entire 80W of power to reduce my electrical bill. The product that consumes the most power in a house is the geyser and switching it of at times to save on electricity is not the solution because you will have to heat up an entire cold geyser for hot water and that requires lots of power. As solar panels and batteries are already low voltage DC itís cheaper and more economical to stay with that power source. I have developed some LED 12v houselights that wouldnít cost anything to run as they are running directly from the batteries that get charged from the solar panels. I have now developed a system that when the batteries are fully charged I take all the available power from the solar panels and feed it in to the geyser element this power is not enough to heat up a geyser but it is enough to keep the geyser at temperature during the day. I have used this system on the 2kw geyser at work and the water remained hot all day without the mains. I am now doing the same tests but with batteries at nigh.