[font=Arial] Solar technologies use energy from the sun to create electricity or pre-heat water for your home. Solar panels and water heating systems allow you to create clean, green energy, helping to reduce climate change effects. Solar PV Solar photovoltaic （PV） systems - often known as solar panels - use energy from the sun to create electricity. PV requires only daylight, rather than direct sunlight, to generate electricity. How does it work? When light shines on the panel it creates an electric field across layers of silicon in the cell, causing electricity to flow. According to the Energy Saving Trust, the greater the intensity of the light, the greater the flow of electricity. Power can be used straight away or linked back into the power grid. What’s involved? You can use PV systems for a building with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, less electricity will be produced. Solar panels are not light and the roof must be strong enough to take their weight, especially if the panels are placed on top of existing tiles. They now come in a variety of shapes and colours, ranging from grey ‘solar tiles‘ that look like roof tiles, to panels and transparent cells that you can use on conservatories and glass to provide shading as well as generating electricity. Planning permission Some local authorities require planning permission to allow you to fit a PV system, especially in conservation areas or on listed buildings. Always check with your local authority about planning issues before you have a system installed. Obtaining planning permission after the system is in place can be difficult and costly. How much does it cost? For the average domestic system, costs can be around £5,000 to £8,000 per kilowatt （kW） installed, with most domestic systems usually between 1.5 and 3kW. Such a system can produce around half a domestic property’s electricity requirements. Solar tiles cost more than conventional panels, and panels that are integrated into a roof are more expensive than those that sit on top. If you intend to have major roof repairs carried out it may be worth exploring PV tiles as they can offset the cost of roof tiles. Maintenance Systems that connect to the grid require very little maintenance, just ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should be checked regularly by a qualified technician, though. Stand-alone systems （not connected to the grid） need maintenance on other system components, such as batteries. Examples of PV systems in the home （opens new window） Solar thermal hot water Solar thermal systems use energy from the sun to pre-heat water for your hot water or space heating needs. There are two types – solar tubes or solar flat plates – which act as collectors of sunlight. How does it work? For domestic hot water there are three main components: solar panels a heat transfer system a hot water cylinder Solar panels - or collectors - are fitted to your roof. They collect heat from the sun‘s radiation. When water is passed through the solar tubes or plates it is heated and then pumped into your hot water cylinder or boiler. The heat transfer system uses the collected heat to heat water. A hot water cylinder stores the hot water that is heated during the day and supplies it for use later. During summer a system can usually provide all your hot water needs, and about half of your needs during the rest of the year. For example, solar thermal can meet up to a third of annual hot water needs for a gas heated three-bed semi-detached house, according to the Energy Saving Trust. What’s involved? Preferably you will need three to four square metres of southeast-to-southwest facing roof receiving direct sunlight for the main part of the day. You‘ll also need space to locate an additional water cylinder if required. Again, always check with your local authority about planning issues before you have a system installed. How much does it cost? The typical installation cost for a domestic system is £3,200 - £4,500. Installing solar thermal hot water could save you up to £40 per year on your hot water bills, according to the Energy Saving Trust. Maintenance Solar hot water systems generally come with a 10-year warranty and require very little maintenance. The householder should check the system each year and a more in-depth check by a professional installer should be done every three to five years （ask your system supplier for exact maintenance requirements）. Case studies on solar thermal hot water from the Energy Saving Trust （opens new window）[/font]