Web-links and information on this page provide a guide to the costs and benefits of installing a solar electricity system at your home, and also to the Feed-in Tariff scheme and to Energy Performance Certificates, which are needed.
You should also see advice on planning permission, insurance and maintenance for a full picture on installing and owning a solar system.
In addition to the solar calculators listed below, the output data from current local installations provide a real-life indication of how much can be generated from solar power in the Wiveliscombe area. This shows that most local installations are slightly exceeding the performance predicted from standard estimates for our zone.
For actual costs you still need to obtain quotes from installers and, as usual, for an investment of this size it is always best to get at least two or three quotes and compare what is being offered.
The prices of panels and installations have fallen greatly since 2010. However, the Government’s Feed-in Tariff is also on a declining path, so you will need to check this too and be aware of when it is next due to change. You can still gain a return on a solar photo-voltaic (PV) system over time and remember that you will make savings on electricity costs too, as you will be consuming less from your supplier through the grid.
By investing in a solar system, you will also be making your own contribution to generating low carbon sustainable energy and turning your home into a clean micro power station.
Factors affecting solar output in Wivey
The three main site factors that influence the performance of a solar PV system are orientation, roof slope and shading.
South-facing roofs generate most, but even those facing East or West still give a good output.
In the Wivey area, panels facing SE or SW should produce about 95% as much as panels facing directly south and those facing east or west should still generate about 82% as much.
The optimum roof angle for Wivey is 38 degrees but angles between 20-50 degrees are still good and, for south-facing roofs, output should only be 2% lower at 25 degrees and just 0.5% lower at 45 degrees.
The table below (click to enlarge) shows how panel performance is expected to vary in our regional zone with different roof slopes and orientations (derived from MCS Irradiance Datasets for Zone 5E).
Shading, even to a small extent and especially during the middle part of the day, can significantly reduce solar generation, so is best avoided. Optimisers or micro-inverters on affected panels can improve the situation, but, if shading will arise, it is sensible to carefully consider how much it could reduce your generation and ensure you receive good advice.
More on these factors and their effect on solar output is given in these blog posts.
The Energy Saving Trust provides further information on inverters and micro-inverters and features of some of the different options.
The Feed-in Tariff (FiT) and Energy Performance Certificates (EPC)
The Government’s Feed-in Tariff scheme provides a payment for every unit (kWh) of electricity generated from your panels, whether it is used by you or exported to the grid. In addition, there is a also a FiT payment for exported units.
The Feed-in Tariff is paid to you by an energy supplier, normally the one that supplies your electricity, but it can be another, such as a green energy supplier specialising in renewables. You apply after the installation is completed and is registered by the installer with the Microgeneration Certification Scheme. Good installers will help you with your application.
Once approved, the FiT is paid for 20 years and adjusted in line with inflation (RPI) every April. Apart from the inflation adjustment, it continues to be paid at the same rate that applied at the time of approval. Future reductions in the tariff, which is now on a downward path, only apply to new installations. You stay on your original rate.
The FiT is tied to the property, so, if you move, the next owner can claim the FiT in exactly the same way and takes over your rights to this, so, as a mini power station, your home earns an income and should be worth more.
The size of the tariff paid depends on the renewable energy technology, with different rates paid for solar, hydro, wind and micro-CHP. The tariff also depends on the size of the system, with most domestic systems being paid at the rate for systems of 4 kW or less.
All units generated from your solar panels are measured on a generation meter which is installed as part of the system. An export meter is optional and is not normally fitted for domestic and small systems, so a ‘deemed’ export amount is assumed for the purposes of FiT payments, which is paid at 50% of the amount generated.
To summarise the situation for an approved system, the full FiT for the system size is paid for every electricity unit generated and, unless metered, there is an additional FiT export payment paid for half of the units generated (with it being assumed that you use the other half).
FiT rates are now reviewed every three months and can fall slightly depending on the number of installations carried out in proceeding quarters, with changes normally announced two months in advance.
To qualify for the Feed-in Tariff, Microgeneration Certification Scheme (MCS) appoved products and installers need to be used and domestic properties need to have an Energy Performance Certificate (EPC) of band D or higher.
The Energy Saving Trust provide very helpful guidance on Energy Performance Certificates, including on how to reach band D. Their free online Home Energy Check will estimate the current EPC band for your property and the costs of energy saving measures, which you can then apply to see how it affects your EPC banding.
Installing solar panels will increase the EPC rating of your property. Previously, a Feed-in Tariff application could be made after installing the panels, where this increased the rating to band D; but, from 15 January 2016, the property needs to have a band D rating before the panels are commissioned to be eligible to apply for the Feed-in Tariff.
If needed, your solar panel installer should be able to arrange an EPC assessment or you can arrange yourself by contacting local assessors.
Ofgem administers the Feed-in Tariff scheme and publishes further guidance on how it is regulated.
Costs and benefits of installing your own solar electricity system
Solar calculator from Energy Saving Trust – shows costs, income, generation and benefits taking account of your roof slope, shading and orientation and installation size.
Solar calculator from Solar Century – clever online mapping works out your roof size and direction, giving a payback breakdown with estimates of total costs and profit that takes account of your location, roof angle, energy use and EPC rating.
Solar calculator from Centre for Alternative Technology – shows costs, savings and environmental impact and takes account of roof slope and orientation (provides a rough guide to costs and income as this calculator appears to be less regularly updated than others).
Other good sources of information
Energy Saving Trust – Solar panels: generate cheap, green electricity from sunlight.
The Government publishes a short straight-forward guide on the Feed-in Tariff and getting money for generating your own electricity and how to apply.
YouGen – A great independent website with lots of information on energy saving, renewable generation, incentives, installers and updated guidance.
Compare My Solar – A price comparison site for installers and system sizes, which includes a solar calculator, but only includes some local installers and provides a rough guide to costs and income, which will need to be verified.