One of the first questions you need to ask yourself when considering solar thermal systems for hot water supply is whether you will need extra storage.

At their simplest, solar thermal systems simply heat water and send it to a standard, insulated hot-water tank, from where your home takes its supply. If the tank contains enough water for your needs, you may be able to opt for what's called a "batch system".

A huge part of the world is already facing a shortage of water supply. A lot of the lakes and rivers in the poor countries of Central Asia have already dried up. Even the rich states in the United States are experiencing the same water shortage. The Colorado River which was once roaring with water is no longer as mighty as it used to be. At present, it does not have enough water to flow to the sea.