FAQ

We've already answered all the most frequently asked questions about solar energy, so you'll probably find out what you need below. In the unlikely event that the answer to your question is not listed please follow the link at the bottom of this page.

Most common FAQ:
1. What is the cost of a solar PV system to run an average home?
2. What size PV system do I need?
3. I’m based outside of the UK, how can you help me?
4. Can I sell the electricity I make?
5. How much energy do your solar tiles generate?
6. What maintenance and cleaning do the systems need?
7. Does solar really work in the UK?

Solar photovoltaic (PV) FAQ:
10. How soon will a PV system pay back the cost of installation?
11. How do solar photovoltaics work?
12. Does the system need batteries?
13. How much electricity will I generate?
14. What happens if there is a power cut?
15. Which electricity supplier should I use?
16. Can I install the myself with an electrician to wire it up to the grid?
17. How efficient are solar panels and tiles?
18. How can the energy benefits of the pv cells be maximised?
19. How can PV glass laminates and flexible thin film PV be used architecturally?
20. How are PV cells affected by soiling?
21. What are the lifetimes of PV products?
22. Doesn't the glazed front reflect light away from solar photovoltaic (PV) modules?

Solar thermal FAQ:
30. Does Solarcentury sell solar thermal systems?
31. Can I use your solar thermal tiles on my house?
32. Can solar thermal in the UK provide central heating or is it restricted to hot water supplementing?

General FAQ:
40. Does Solarcentury service the whole of the UK?
41. How can I find a certified installer?
42. Does Solarcentury have any graduate or job opportunities?
43. Do you sell solar sign lights, garden lights or other battery systems?
44. What are the effects of shade?
45. How is the angle of optimum panel inclination found for different latitudes within the UK?
46. How do the panels perform at different angles and orientations?
47. What are the main detailing points to consider?
48. What are the relevant codes of practice and articles of legislation?
49. What are the Health and Safety issues?
50. What sort of projects are suitable for solar installations?
51. Can I get trained by Solarcentury to become a solar installer?

Most common FAQ - Answers:

1. What is the cost of a solar PV system to run an average home?
There is no simple answer to this question since different homes energy consumptions vary so dramatically.
It all depends how many kWhs (kilowatt hours - or units) you consume. Some people use a few thousands units, others use thousands more. Without knowing how many units you use we can not advise on the most suitable system. It makes sense to do as much energy efficiency as possible BEFORE thinking about installing solar, so you do not need to buy such a large system.
If you know how many units you use (per year) and would like to work out a rough cost:
Divide the number of 'units required per year' by 850 (to tell you how many kWp - kilo watt peak) you will need
Then multiply that number by £5000 - £6000 (rough cost per kilowatt peak)
That should give you a very rough idea of cost, although you will need to pay for installation and may also need scaffolding if you live in a two storey home.
It is not essential to provide ALL of your homes electricity via solar PV (since you will still be connected to the national grid), even half will make a serious reduction to your carbon footprint.

2. What size PV system do I need?
As with the cost question above, there is no standard answer to this question since it depends how much energy you need to generate, which in turn depends on how many kilowatt hours you consume. Once you know that you can use the information above to work out how much PV you will need.
1 'kilowatt peak' generates 850kWhs/year, and takes up about 7 square meters of roof space.

3. I’m based outside of the UK, how can you help me?
We can wholesale orders over 5kWp and provide you with links to installers in your country. If you have a wholesale enquiry please contact the wholesale team. If you are a resident of France, Spain or Italy, please contact our in country offices. We are NOT currently able to sell our C21e solar electric roof tiles anywhere outside Europe.

4. Can I sell the electricity I make?
Yes. Please see our page on Exporting Electricity for more details, the best rate is at the moment is 28p/kWh from Scottish and Southern Energy.

5. How much energy do your solar tiles generate?
This depends on how many you have installed. Please see the systems and kWh data listed on the back page of the C21e brochure.

6. What maintenance and cleaning do the systems need?
Solar photovoltaic systems are silent in operation, have no moving parts and require no maintenance. Solar thermal systems have a few moving parts (inside the pump) but these are virtually maintenance free, you may need to replace the anti-freeze in a solar thermal system after about five years. Most of the time the rain will keep the modules clean. However, a build up of dirt can affect system performance. The modules can be cleaned with either a hose or, if possible, soapy water and a non abrasive brush.

7. Does it really work in the UK?
Yes. The cells in the tiles only require daylight to work, and will even generate energy on cloudy days. UK irradiance levels currently stand at 1000W/m2/year for London, with a range of 800W/m2/year to 1000W/m2/year across the UK. There is little difference between solar irradiation in the Scotland and the south coast of England. In fact, solar electric (PV) panels are routinely used in the polar regions to supply power for test equipment. The UK has similar irradiance levels to Germany and the Netherlands.

Solar photovoltaic (PV) FAQ - Answers:

10. How soon will a PV system pay back the cost of installation?
To use an example, a typical domestic retrofit system saves over a tonne of CO2 per year and £350 per year off electricity bills at today's prices. The system is warranted for 20 years and will last another 20 years beyond that. In addition, the Government's grant programme offers guaranteed domestic PV grants of up to £2500 till mid 2010 towards the cost of installation (see www.lowcarbonbuildings.co.uk)
Micro-generating customers of Scottish and Southern Energy received the news that from 1st April 2009 they will be paid 28p per unit for their exported electricity. This means that the typical UK domestic PV owner will be saving well over £350 per year on their electricity bills at today's prices. On this basis, a typical domestic PV system will pay back in about 13 years. On top of that the value of their property will have increased as a result of their decision to install PV.
Additionally, the supposed 30 year working lifetime of photovoltaics is very much an underestimate. Some of the first solar panels manufactured by Sharp
and installed in Japan over 40 years ago are still generating electricity today. And that's using half century old technology.
All in all, putting solar panels on your roof now makes more sense (in terms of economic value) than putting money into a pension, or probably any sort
of savings account at the present rates of interest.

11. How do solar photovoltaics work?
Daylight hits the photovoltaic cells and is converted to clean electricity. The inverter converts the electricity from direct to alternating current, for use in the home. When the solar energy system is producing more power than is needed it is exported to the grid. At night, power is imported from the grid in the normal way. See our page on How photovoltaics work.

12. Does the system need batteries?
No, the systems Solarcentury sells are connected to the national grid. In the night, when the tiles are not generating energy, electricity is bought from the utility company in the normal way. Any excess electricity generated during the day, for example when you are at work, is sold back to the utility company.

13. How much energy will I generate?
This depends on how much PV you have installed. Please see the system sizes and kWh data listed on the back page of the C21e brochure

14. What happens if there is a power cut?
Our photovoltaic systems for homes are entirely grid connected. If there is a power cut your system is automatically switched off. This is a safety measure designed to stop electricity leaking on to the national grid and to protect individuals who may be working to restore the power supply.

15. Which electricity supplier should I use?
Currently the trend amongst suppliers is not to install export meters but to pay a fixed amount per kilowatt peak installed. This means that you will be rewarded for the electricity generated from your system even when you use it in your home – potentially doubling its value. Most of the big utilities will buy back the energy you generate for the same price as they sell it to you although, if you do need to switch supplier it is not a complicated process. Please see our page on Exporting Electricity for more details.

16. Can I install the myself with an electrician to wire it up to the grid?
A Sunstation (system of modules on top of your roof) is only designed to be installed by a qualified PV installer. If you installed a C21e system yourself it would not be covered by our warranty. We do sell everything you need but this would normally be through our installer. If you would like to be put you in touch with one in your area please fill our application form.

17. How efficient are solar panels and tiles?
The 'efficiency' of solar panels is less relevant than you might imagine, the sun contains an incredible amount of energy! More important is the kWh/kWp (kilo watt hours (or 'units') per kilo watt peak) you will generate. The government quote this as 850kWhs/kWp for the UK, but we have seen 1000kWhs/kWp for some system in the UK.
So if you had a 4kWp system (about 30m2) you could generate 4x850=3400 units a year (at the gov figures), which is more than you need in a 3 bed house with all mod cons AS LONG as you are 'energy aware' and not frivolous with your usage!

18. How can the energy benefits of the pv cells be maximised?
Orientation, shading and the temperature of the PV elements all impact on their output and must be considered at the design stage. The best orientation for solar PV in the UK is south facing at 30 - 40°.
Of course, the more energy efficient the building, the greater the overall benefit of the PV cells.
Some PV products have now been designed to provide thermal insulation as well as electricity - eg flat roof systems and solar metal roofing systems that include insulation and solar glass laminates with low emissivity glass.

19. How can PV glass laminates and flexible thin film PV be used architecturally?
PV glass laminates are attractive and well suited to facades and transparent roof tops. They can be fitted to standard curtain walling structures and are suitable for any application where glass is used, as long as there is a reasonable level of light present. Low emissivity glass can be used to give additional thermal insulation benefits, or a PVB laminate can be used for the extra strength required by a roof top.

20. How are PV cells affected by soiling?
The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees. In extreme cases dust may cause a power reduction of about 10%. At low tilts horizontal glazing bars can trap debris which could lead to shading of part of the array. The design of the system should aim to minimise uneven soiling.

21. What are the lifetimes of PV products?
Solar modules have a manufacturers warranty of 20 years and a working lifetime of 40 years and beyond. Modules of all types usually have a twenty year warranty, as do most thin-film integrated products. PV glass laminates usually have a ten year warranty. These times are only a rough guide and should be checked for each specific product.

22. Doesn't the glazed front reflect light away from solar photovoltaic (PV) modules?
Not really, no. Solar PV modules constructed with a glass front have two characteristics that reduce light reflection. In order to optimise electrical yield the glass is treated with an anti-reflective coating which greatly increases the transmittance through the glass to maximise the amount of light reaching the solar cells.
Secondly, the outer face of the glass has a slight granular texture. The result is a matt like finish rather than mirrored surface which again maximises yield. These two characteristics greatly reduce reflection from the glazed front face of solar PV modules when compared with conventional glazing.

Solar thermal FAQ - Answers:

30. Does Solarcentury sell solar thermal systems?
We only sell solar thermal system to housing developers looking to meet the Code for Sustainable Homes.

31. Can I use your solar thermal tiles on my house?
At the moment it is not possible for us to sell our solar thermal tiles to individuals, they can only be used by housing developers.

32. Can solar thermal in the UK provide central heating or is it restricted to hot water supplementing?
Space heating from solar is far more complex (than heating hot water) since it requires integration with your radiator / under floor heating
system, rather than just the hot water tank. It IS possible, but not something Solarcentury specialise in. The most efficient thermal systems are evacuated tubes, but they are also the most costly and a decent flat plate collector will still work very well in most situations and provide a more cost effective solution.

General FAQ - Answers:

40. Does Solarcentury service the whole of the UK?
Yes. Our network of recommended installers, accredited to MCS standards (Microgeneration Certification Scheme), are fully trained to install photovoltaic systems throughout England, Scotland, Wales and Northern Ireland. Solar energy systems can be easily 'retro-fitted' to existing properties or, if you are re-roofing, building a new home or other property see our range of pre-engineered PV tile and slate systems.

41. How can I find a certified installer?
To find your nearest installer for solar tiles please see our map of roofers or, to be put in touch with your local installer for a 'retro fit' (on roof) installation please fill our application form.

42. Does Solarcentury have any graduate or job opportunities?
We do offer work experience opportunities but are unfortunately not able to pay for student's time. Please send through details of your skills, what
types of things you would like to work on and any learning objectives to recruitment@solarcentury.com or see the jobs section.

43. Do you sell solar sign lights, garden lights or other battery systems?
No, we do not sell any battery systems, all our products are designed to be linked to the national grid.

44. What are the effects of shade?
Shading is critical. Minor shading can result in significant loss of energy. This is because the cell with the lowest illumination determines the operating current of the series string in which it is connected. Many modern modules use bypass diodes to minimise shade effects; but these effects must still be considered, preferably in the first stages of building design. Watch for landscaping, trees and even handrails.

If shading is unavoidable, or poor light is expected on a regular basis, the best types of PV to use are amorphous thin-film (eg Kaneka/Unisolar products), or hybrid (mixing monocrystalline and amorphous technology - eg Sanyo HIT modules).

45. How is the angle of optimum panel inclination found for different latitudes within the UK?
The maximum total annual solar radiation is usually at an orientation due south and at a tilt from the horizontal equal to the latitude of the site minus approximately 20 degrees. For example 30 degrees is an optimal tilt in Southern England, increasing to almost 40 degrees in Northern Scotland. See our orientation and pitch table.

46. How do the panels perform at different angles and orientations?
If the optimum angle is not achievable, over 90% of the maximum annual energy can still be achieved at 10 degree and 50 degree tilts. South-facing vertical facades generate around 70% of the maximum. See our orientation and pitch table.

47. What are the main detailing points to consider?
The main points to remember are:

• Method of fixing/ integration into the fabric must be detailed.
• Ensure that the fixing does not cover or shade any part of the PV cells.
• PV laminates are often constructed with only a narrow border.
• The fixing must allow for thermal expansion without breaking the glass.
• Weather sealing involves standard construction practices but all materials must be suitable for the temperatures likely to be met (i.e. temperatures at the back of the modules can rise to 80º if they are poorly ventilated or higher if they are directly insulated).
• The mounting option must allow for safe maintenance and possible replacement of individual modules.
• The life of the support structure must be at least that of the PV array. The preferred materials are aluminium, stainless steel or glass-fibre. Protection from corrosion is important especially as residual currents may be present.
• Wind loading
• Any extra weight
• How and where to run electrical wiring ( this may penetrate the waterproof skin)
• Where to place junction boxes.

48. What are the relevant codes of practice and articles of legislation?
British Standards
BS EN 61215
BS EN 61646
The Electric Supply Regulations 1988
The Building Regulations 1991 (and amendments)
The Construction (Design and Management) Regulations 1994

A 'Power purchase agreement' will need to be negotiated if electricity is to be sold. This is not as tricky as it sounds as electricity networks and supply companies are legally obliged to cooperate with solar installations.

49. What are the Health and Safety issues?
The main issues to be aware of when appraising PV for CDM are:
Weight: Modules may be heavy with some exceeding 50kg.
Toxicity: No PV module releases sufficient toxic materials to cause any harm during installation or maintenance. A small proportion of PV contains cadmium, the oxides of which are toxic in very small doses. Some of these may release toxic dust if crushed during disposal. None of the PV products supplied by Solar Century contain any cadmium. For a more detailed appraisal see the DBERR guide : Photovoltaics in Buildings/ Safety and the CDM regulations.

50. What sort of projects are suitable for solar installations?
A project with a brief incorporating social and technical innovation is an ideal candidate for building-integrated PV (BIPV). The most important aspect to consider is the location of the site. The solar installation must receive as much light as possible. Shadows cast by tall trees and neighbouring buildings must be kept in mind during the design process. The best location for solar PV is obviously on the south-facing roof or side of a building.

51. Can I get trained by Solarcentury to become a solar installer?
Please see our training page.

Still got a question? Fill in our 'Ask A Question' form and we will reply as soon as possible. NB we do not have time to answer questions which are already answered above.