By Jeff Harrop

The sun delivers energy in three distinct forms. First is infra red, which is felt as heat on a sunny day and has a wavelength that is long. Next is visible light which has a medium wave length. Lastly is the UV range, which is not visible and has the shortest wavelength. 

Solar hot water collectors can capture all of these wavelengths and make energy from them. This means that all of the 1000 Watt/m2 are capable of being used to make heat. It does not mean that the products on the market can do this. Solar Photovoltaic (PV) relies on a wavelength that can penetrate into the silicon that will provide energy to dislodge an electron for energy production. That energy is in the wavelength of visible light and into the UV spectrum. Therefore only 50% of the energy from the sun can make electricity. To date, that is the why we see a lower production of solar PV panel versus solar hot water collectors.