There are a few different types of solar hot water systems. Hot water systems have their place in the solar scheme of things. However, traditionally hot water solar systems were first implemented before solar power and for a long time were the primary way to save money. Over time however, with more solar power experts, distributors, and avenues for solar PV (photo voltaic) power hot water systems are increasingly becoming assist equipment with the primary equipment becoming power equipment that also can be used to heat the water. Unfortunately, hot water systems can not be used to provide power so they provide only one function (hot water) instead of both hot water and power from PV systems. The issue with hotwater systems are once they reach temperature they often will have excess temperature vented by way of water exiting on the roof which is not thrilling to see from a water conservation point of view and secondly once they reach temperature they just sit there doing nothing. Where as power from a solar power system can be used for all the power in the house including the power to heat the cylinder, and once the cylinder is up to temperature other stuff in the house uses the power all day it is generated, and if nothing is using it then it goes back to the grid and provides a feed in tariff by the kw from the electric retailer.
Evacuated tubes- higher pitch the better, cheaper to fix than flat panels, and operate at higher temperatures usually. Can be used for pools, and spas as well.
Flat panel- good option if you have roof space but can be expensive to install.
Pool heating- rubber large area volume heaters which are really good at heating for pools due to volume but not capable of cylinders really.
wetback systems- combined with a solar power system, wetbacks are probably the best solution available. In winter when solar is at its lowest, usually you will have your fire going which will heat up the cylinder before power is used. In summer when solar is at its best, you don’t have a fire going and rely on solar. Best option with solar power in our opinion.
gas- always is an option, and for camp grounds or hostels instantaneous gas is the way to go over flat panels or evacuated tubes because of the volume of water used and the inability of solar tube or panels to provide the heat for the volume unless cost is not a concern and you have a huge amount of roof space which most camp grounds don’t. Even hotels will be much better off using the roof space to provide power than trying to heat high volumes of water.