Solar Electricity (Photovoltaics or 'PV')
Solar photovoltaic (PV) technology on a small scale is familiar to most people in the UK. It is used to power calculators, road signs, toys and phone chargers. It takes light from the sun, and uses it to run the appliance. Solar PV panels for electricity generation work on the same principle, just at a larger scale.
Daylight is all you need to get electricity from the panels. It is an unlimited resource that’s never going to stop shining (even though it doesn’t always feel like that in the UK). Although more electricity is produced on sunny days panels work well on overcast days too.
Is solar electricity suitable for my home?
Ideally a solar PV system should face between south east and south west, and be free of shade. For best performance they should be angled at 30 to 40 degrees – although you will still catch a reasonable level of sunlight at angles of 20 – 50 degrees.
Shade falling on the roof will reduce the performance. How much it affects it by depends on type of shading: close structures such as gable windows or chimney stacks can reduce output significantly as they will tend to throw shade on the panels for most of the day.
Further away objects such as trees or a neighbouring house may not block the sun during summer, but create shade when the sun is lower in the sky in winter. There are several gizmos available to help installers predict the impact shading will have on estimated performance. Shading issues can be avoided by inserting micro inverters, however, this will incur extra costs. Please click here for further information.
Solar panels weigh quite a bit, so your roof must be strong enough to hold them. If you need to re-roof, you can do so using solar tiles. These are more expensive than panel systems, but if you are re-roofing anyway, it can be more cost-effective to re-roof with solar tiles than to use conventional tiles and put panels on top.
Solar PV systems are easy to install, need virtually no maintenance and are estimated to last 40 years. They are suitable for use in urban areas which wind or hydro systems don’t tend to be.
The energy efficiency requirement
New energy efficiency requirements for the feed-in tariff (FiT) for solar PV start on 1 April 2012. As a result, the full FITs rate is only available for buildings which have an Energy Performance Certificate of band D or above. Currently just under half the UK housing stock meets this criteria.
The installation of solar panels is, in itself, an energy efficiency measure and will bring some properties that are currently band E to band D. However, don't assume that is the case. The EPC algorithms are complicated, and the only way to be sure is to run the data through the software. Don't go ahead on a 'guesstimate' from a domestic energy assessor (DEA) or your installer.
Installations that don't meet the criteria, will get a significantly lower level of generation tariff: 9p per kW instead of 16p per kW for systems of 4kW or less (15.5p from November), so you may need to take additional energy efficiency measures to get up to the required standard. You must send the EPC certificate to your FiT supplier when you register for the tariff. They will not change the FIT rate retrospectively if you achieve band D at a later date.
Some homes are unlikely to reach D without significant investment. There will be exemptions for buildings that cannot get an EPC, but they are expected to be few and far between.