Solar thermal energy is typically stored in a hot water cylinder and so the output of the system can be used when required, i.e. you can be out while the sun is shining and come home to use the energy that was collected in your absence. Solar PV can be stored but this is an expensive addition at the moment, the alternative is using the electricity as it is produced which can be difficult of you do not have a constant base load in your house. If you produce electricity that is not used in house it is exported to the grid and donated to the various utilities for free.. There is talk of a Feed in Tarriff coming which will allow for payment in this scenario but it may be a few years away.

The amount of south facing roof space available to you may sway your decision, if small and urban you should consider maximising the amount of solar energy you can produce which will favour solar thermal. So if you have a small roof space the best solar panels would be solar thermal as you get more useable energy from that system. This doesn’t exclude solar pv which can be added at a later stage. If you have a large south facing roof space then there should be enough room for both types of solar panels.

Solar thermal systems pay for themselves in 1-5 years approx. (all depending on your current and future water use and future energy prices..) Solar PV systems under the current scenario can take 15 – 20 years to pay for themselves but again it all depends on how the system is used. The best solar panels in this scenario are probably the ones that last the longest as they will continue to produce revenue for a longer period so it can pay to invest more in quality.