Seen initially as capital intensive investment, inevitable rising fuel costs, the accelerating drive towards adopting renewable technologies and a radical reduction in CO2 emissions is seeing the demand for using Green Energy push the interest in installing Solar Water Heating. The importance of solar energy means it is a significant category in the World Energy Renewable Network (WREN) which is a network of worldwide organisations promoting environmentally safe and economically sustainable renewable energy.As a result, the heating installation market is changing and the new technologies are not just for heating private swimming pools or for supplementing the water heating systems of those already actively supporting alternative energies, it is now being used extensively, not only in the domestic sector but also in the commercial and local authority/housing association developments, including schools and colleges.This is good long term employment news for those either in the plumbing or electrical trades who wish to upgrade their skills and knowledge or about to enter the industry by training to be a electrician or learning to be a plumber.Although the installation of a solar system may be more capital intensive than a straight forward boiler system, the fuel cost savings will be progressively higher year on year and maintenance should also be reduced. With the Government emphasis now firmly on whole life costing, the initial capital cost has much less significance than before and running costs much greater importance.Solar water heating is based on the principle of heat from the sun being absorbed by a collector, which is transferred to a water system supplying a cylinder to preheat domestic hot water. Much development has been made with the design of the collectors and both system and collectors must be matched to each other - with the property - just as with any other type of heating.Solar photovoltaic(PV) energy is simply the conversion of sunlight to electricity. It is a particularly attractive technology because there are no moving parts, no emissions, no noise and long life. It can be used to power pumps (for instance on a solar water heating system) and provide the power for low energy appliances and lighting.Photovoltaics ranges from single stand alone systems to those which are fully grid connected, from a few Watts output to multi MegaWatt systems and even GigaWatt networks.