Solar Panels Explained

Updated: Mar 31


Photo © Oast House Archive (cc-by-sa/2.0)

Solar panels as a technology are unlikely to be a 24/7, whole home answer for either hot water (Solar Thermal) or electricity supply (Solar PV). Put in simple terms the sun does not shine all day or all year round. Therefore, they should be considered as a component of your supply and planned into a complete system. The sun’s energy is free and energy from the grid is not so savings can be made, and you will be reducing your carbon footprint. For an average installation in the UK today, a solar thermal system would take 7 years (assuming RHI claim) and a Solar PV 14 years (assuming SEG claim), to repay the initial investment. Clearly these timescales would be impacted by energy price changes and renewable incentive changes in the future. The case is currently unproven in terms of the value Solar Panels add to your property. It is generally accepted that a higher EPC rating will increase the value of a property from a buyer’s perspective, but the value added versus cost attributed to Solar Panels is far from clear. Upfront costs for the average solar system are around £5000, check out the available grants for solar PV and solar thermal to see how you can finance this.


To take advantage of this free energy source will require an area of some 5 to 10 square meters for a thermal system and 10 to 20 square meters for PV. Ideally this should be south facing, unshaded and at 30 to 40 degrees pitch. In most cases this will be most easily be achieved using roof space but could also be a free standing/hung frame. Positioning on platforms from south through to east or west is possible, but efficiency will decrease and beyond east or west facing is not recommended.


In most cases solar panels are a permitted development, but this may not be the case with listed properties or in conservation areas.


Solar PV

Solar PV (photovoltaic) panels capture the sun’s energy and convert it into electricity. Solar PV cells are made from layers of semi-conducting material, usually silicon, which are combined to form a module (several modules forming an array). When light shines on the material, electrons are agitated, creating a flow of electricity. The cells do not need direct sunlight to work and can work on a cloudy day, however, the stronger the sunshine the more electricity generated.


Modules and arrays do come in a variety of shapes and sizes and although most PV systems are made up of rectangular panels that fit on top of your roof, they are flexible in terms of using any appropriate space. Electricity generated is direct current (DC), so an inverter is installed to allow use with alternating current (AC) household appliances.

Solar panels can be “built in” to a roof rather than sitting on top of the tiles and Solar tiles are available to be used in place of ordinary roof tiles. Neither are normally as cost-effective as panel systems and are usually only considered where panels are not appropriate for aesthetic or planning reasons.


With a domestic PV system, there will be times when the electricity you generate is more than you can use or store, so the surplus can be exported to the grid to be used by somebody else. Following the closure of the feed-in tariff scheme in March 2019, the smart export guarantee (SEG) was introduced to provide financial support to small-scale renewable energy generators for the electricity they export to the grid. See our article on solar PV grants for more information.


Solar Thermal


Solar water heating systems use solar panels, called collectors, fitted to your roof. These collect heat from the sun and use it to heat up water that is stored in a hot water cylinder. A boiler or immersion heater can be used as a back up to heat the water further to reach the temperature you want.


The two types of solar water heating panels available are, evacuated tubes, made up of a bank of glass tubes mounted on the roof tiles, and, flat plate collectors, fixed on the roof tiles or integrated into the roof. You will usually need to replace the existing cylinder or add a dedicated cylinder with a solar heating coil. A conventional boiler or immersion heater can be used to make the water hotter, or to provide hot water when solar energy is unavailable.


Solar Thermal panels can benefit from payments through the UK Government’s Renewable Heat Incentive (RHI), as well as the Assignment of Rights helping with upfront costs. See our article on solar thermal grants for more information.


Larger solar thermal panels can also be arranged to provide some contribution to heating your home. In most cases, however, the amount of heat provided is generally very small and would not normally be considered worthwhile.

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