Solar Water Heating Collectors need radiation to heat the water. So they work best without clouds and plain sunshine. The outside temperature is irrelevant, so even a sunny winter day will give you good results on your Solar Water Heating Collector.
We install Flat Plate Collectors from local manufacturers and importers. Our experience shows that those collectors are the better choice in most South African weather conditions. The alternative Evacuated Tube Collector is designed for European conditions and often starts to boil in summer. However, there are very limited scenarios when we recommend an Evacuated tube Collector.
The main mistake most people make when going Solar is to keep their existing storage capacity. With Solar Water Heating you need to increase your geyser size. This is simply because you want to have enough hot water heated by the sun to get you through the evening and the next morning before the sun can heat the next batch. If your storage is too small, your element will heat your water in the morning and you miss out on the free energy from the sun.
The pay-back period of a Solar Water Heater depends on your demand. As more hot water you use, as faster is the pay-back. On average a Solar Water Heater pays itself after 2,5 years.