For many people, solar technology only conjures an image of glossy panels on the roof used to generate electricity. That solar electric technology is called a photovoltaic (PV) panel. A PV cell converts 16-20% of the solar radiation that reaches it into electricity while squandering 80-84% of the available solar resource. PV technology has the potential to be a very useful renewable energy tool, but the current generation is far from ideal.
On the other hand, solar thermal technology can convert over 90% of available sunlight directly into usable heat. Solar thermal products provide a more limited range of uses than PV products, but solar space heating and solar water heating collectors offer a greater return on investment and higher carbon emission reductions for a cheaper initial purchase and installation cost. In most cases, PV technology takes more than 20 years to pay for itself, while solar water heaters should take less than a decade to do the same.
If you are just beginning to explore renewable energy products, solar water heaters are the ideal first step. If you own an existing PV or wind power system, solar water heaters are still a wonderful supplemental investment that will bring you one step closer to a zero-energy building.