Your Roof Making sense of solar 2 Your Roof Making sense of solar 3 Your Roof Making sense of solar 4 Your Roof Making sense of solar 5 Your Roof Making sense of solar 6 Your Roof Making sense of solar 7 Your Roof Making sense of solar 8 Your Roof Making sense of solar 9 Your Roof Making sense of solar 10 Your Roof Making sense of solar 11 Your Roof Making sense of solar 12 Your Roof Making sense of solar 13 Your Roof Making sense of solar 14

Your Roof

. Making sense of solar

Solar power

.Q & A

IS MY ROOF SUITABLE?
HOW MUCH IS A TYPICAL SOLAR PV SYSTEM?
HOW MUCH MAINTENANCE DOES SOLAR PV REQUIRE?
WHAT IS THE FEED-IN TARIFF (FIT) SCHEME?
SO HOW MUCH BETTER OFF WILL I BE?
HOW DO I QUALIFY FOR FITS?
HOW DOES SOLAR WORK WITH THE GREEN DEAL?
HOW DO I FIND AN INSTALLER?
HOW DOES WHERE I LIVE AFFECT HOW MUCH SOLAR I CAN GENERATE?
HOW MUCH POWER WILL I GENERATE?
WHAT KINDS OF SOLAR PANELS ARE AVAILABLE?
WHAT IS THE ENERGY PAYBACK ON SOLAR PANELS?
HOW LONG DO SOLAR PANELS LAST?
HOW MUCH CARBON WILL MY SOLAR PANEL SAVE?
WHAT DOES kW(p) ACTUALLY MEAN?
WHAT IF IT’S NOT SUNNY?
WILL SOLAR IMPROVE THE VALUE OF MY HOME?
WHAT IS BETTER, ‘FREE’ SOLAR OR BUYING THE SYSTEM MYSELF?
I CAN’T AFFORD TO BUY SOLAR OUTRIGHT. WHAT HELP IS THERE?

 

IS MY ROOF SUITABLE?
The majority of roofs are suitable for solar power. The only roof that we would never recommend is north facing. South-facing roofs are best and the angle should be between 30 to 40 degrees for the best performance. However, east and west roofs produce only up to 15% less power than a roof facing due south. Flat roofs produce around 10% less than the most optimal southern roof. Your roof should not be shaded.

You will also need room, usually in your loft space, for your inverter. This turns the power produced by your solar panels into power you can use in your home. This needs cool air to circulate around it, and usually requires just over a cubic meter of space.

Finally your roof needs to be strong enough because solar modules are heavy. The great majority of roofs are strong, but this is a factor your installer should check. See our video Positioning a PV Module.

HOW MUCH IS A TYPICAL SOLAR PV SYSTEM?
A good price for a 4kW system is around £6,500. 4kW is a large system, suitable for a large family home. In reality most homes will probably have a smaller system. However, as the cost of solar PV has been coming down, average scheme size has been increasing. If you want high efficiency panels they will be more expensive. If you want solar modules integrated into roofing slates these will be more expensive still, but they are very attractive and can make good economic sense if you need to replace your existing roof slates.

HOW MUCH MAINTENANCE DOES SOLAR PV REQUIRE?
Solar PV is often known as a ‘fit and forget’ technology because it requires so little maintenance. Apart from keeping it relatively clean, there is nothing more to do. Solar PV systems are usually guaranteed to last over 25 years. During this time it is likely that you will need to replace the inverter.

WHAT IS THE FEED-IN TARIFF (FIT) SCHEME?
The Feed-In Tariff (FIT) scheme is a Government scheme to make it cost-effective for you to invest in solar power. The FIT pays you a premium rate for each unit of power (kWh) your solar system generates. For systems under 4kW(p) in size, which is the case for the great majority of domestic systems, the FIT rate is currently 14.38p kWh and will remain at 14.38p at least until before July 1st.

This means if you install solar now (as of 1st April) you will receive 14.38p for each unit of power you generate. And this payment will go on for 20 years. Each year it will increase in line with inflation so in real terms the payment stays the same. Unless you rent your home out, these payments are tax free.

At the same time each unit of solar power you consume in the home avoids you paying for electricity off the grid, currently around 15p kWh. Therefore your energy bills will be lower. In addition you can receive 4.77p kWh for each unit of electricity that you export as surplus to the grid. Your supplier is obliged to make these payments. Rather than metering them this is usually estimated at 50% of all the power you generate. You can use the calcuator on this website to estimate your returns.

SO HOW MUCH BETTER OFF WILL I BE?
This depends on a number of factors. The more time you spend in the home during the day the more you can use the power from your solar installation, and avoid paying for grid electricity. Use our calculator (link button on the right) to give you a rough estimate. STA members have a more sophisticated version of the returns calculator which includes roof orientation and angle. Your installer should provide you with accurate information on how much solar power will improve your household finances.

Remember, the Government has historically greatly underestimated the rate of electricity bill price rises. This means in practice you are likely to save more money on your energy bills in future than official figures often suggest.

HOW DO I QUALIFY FOR FITS?
You must ensure that your installer and the equipment you install is new and MCS certified. In addition your home must at least meet Energy Performance Band D. Half of UK homes already meet this level. However, installing solar can push a Band E property into Band D. Your installer should be able to advise you on your home rating and whether you will need to install thermal efficiency measures in order to qualify for the highest FIT. If your home fails to meet Band D at the point when your installation is completed, you will only be eligible for a FIT rate of 6.61p kWh. It really is worth going for high levels of thermal and electrical efficiency in your home because this can save you a lot of money, and help the environment. Remember changing your behaviour – not leaving the heating on if you’re out and turning off equipment on standby – can save a lot of money too.

In order to claim for FIT payments from your utility supplier (energy company) you will need to provide your supplier with the MCS number of your PV installer and the FIT eligibility certificate your installer provided. Your utility supplier will then cross-reference your installation with the central FIT database and payments will be paid to you at intervals. In most cases the FITS payment is made by personal cheque to the person named on the household utility bill every quarter. Many installers will set this up for you.

HOW DOES SOLAR WORK WITH THE GREEN DEAL?
Wowzer this is complicated! Payments from the FiT scheme are not eligible under the Green Deal Golden Rule. That means you cannot expect solar power under a Green Deal package with repayments made from the FIT scheme. However, the savings on your energy bill that solar delivers are eligible. So a proportion of your solar power system can be paid for under the Green Deal. Your Green Deal Assessor can work out what that proportion is. You would then need to pay for the remainder yourself.

HOW DO I FIND AN INSTALLER?
There are a number of good places to start. See the Renewable Energy Consumer Code website. Check the MCS register. Or check the STA membership list. You can find links to all these groups on the More Info pages. All members of the STA have to be a member of the REAL Consumer Code. See our section on What to Ask Your Installer.

HOW DOES WHERE I LIVE AFFECT HOW MUCH SOLAR I CAN GENERATE?
Maps produced by the Met Office show that different regions of the UK benefit from different levels of solar radiation. The region with the highest solar resource is the south east. Each kW(p) of solar installed in the south east will generate 1132kWh of solar per annum. The lowest generation is in the Shetlands at 714kWh per annum. Cornwall receives 1093kWh per annum.  The most recent map is available here: solar radiation map. Check out how strong the solar resource is in your region! You can then use this to estimate your returns in our solar Calcuator.

HOW MUCH POWER WILL I GENERATE?
As above, this depends on where you are, you roof orientation, what kind of solar power you have installed and how big your system is. However, a typical system of around 2.5kW – 3kW(p) will readily meet half the average electricity needs of the average UK home. This can be increased to 70% using battery storage. Domestic battery storage systems are increasingly available on the market.

WHAT KINDS OF SOLAR PANELS ARE AVAILABLE?
There are three basic types of solar panel available. Solar is also available as Building Integrated PV, where it is embedded in roof tiles. Solar cells can also be embedded in glass. If you have only a small roof space it makes sense to go for the highest efficiency solar panels to optimise how much solar power you can generate.
Monocrystalline solar is made from a single crystal of silicon. These are the most efficient, but also the most expensive cells to produce.
Polycrystalline solar is made from blocks of silicon made up of many crystals. Both forms of cystalline solar are brittle and must be mounted in rigid frames.
Thin-film solar requires only a thin film of silicon on a surface that can be flexible – for example on plastic. It is cheaper, but less efficient, so it needs a larger area. Some thin-film solar panels look lovely on historic properties with dark slate roofs in conservation areas.
You can be confident that the great majority of systems available on the UK market are good quality. However, we would not recommend investing in second and third tier Chinese solar modules. The best Chinese solar panels are very good. However, if you are buying Chinese modules always check these are ‘first tier’ product.

WHAT IS THE ENERGY PAYBACK ON SOLAR PANELS?
Energy Pay Back Time (EPBT) means how long it takes for a solar panel to generate the power that was required to manufacture it. Once this point is reached solar technology is effectively providing power completely free of carbon and reducing our dependency on fossil fuels. Some parts of solar PV manufacture are energy intensive, but manufacturing processes are becoming increasingly efficient. We recommend this interesting article by Professor Fthenarkis, Director of the Centre for Life Cycle Analysis. In the 1970s it took 40 years of power generation for solar PV to recover the energy used in its manufacture. That is now down to just 0.5 years for the most efficient systems in optimum locations today. In reality payback times will vary depending on output and the type of panel installed – typically between 0.5 and two years. The calculations in this article are based on International Energy Agency “Methodology Guidelines on Life Cycle Assessment of PV Electricity.”

HOW LONG DO SOLAR PANELS LAST?
Solar panels have no moving parts which makes them unique amongst power generation technologies. It means little wear and tear. They are therefore exceptionally long lasting. Solar panels manufactured in the 1970s are still generating power today, so we don’t really know how long they last – certainly 40 years or more. Over time the output of solar panels reduces. At the Solar Trade Association we assume that panels lose around 10% of their output after 10 years. Most solar panels are guaranteed to lose only 1% efficiency per annum and most are guaranteed to last for 25 years.

HOW MUCH CARBON WILL MY SOLAR PANEL SAVE?
Around 1 ton per annum – show calculation.

WHAT DOES kW(p) ACTUALLY MEAN?
The size of your system will be expressed in terms of kW(p). This refers to how much electricity your system can generate at peak performance (p stands for peak). This is the optimum output your system could technically achieve.

WHAT IF IT’S NOT SUNNY?
Solar generates the most power when it is sunny and cold. Heat can actually reduce the performance of some solar modules. However, even on an overcast day your system will generate about a third of the power it would generate in direct sunlight.

There is a widespread perception that solar suits only sunny countries. Actually a study by Oxford University’s Environmental Change Institute showed that there is a surprisingly small difference between the output of solar panels in summer in the UK and solar panels in Mediterranean countries.This is because heat can reduce performance and the longer daylight hours in northerly latitudes compensates for lower output.

WILL SOLAR IMPROVE THE VALUE OF MY HOME?
The Renewable Energy Consumer Code scheme does not like installers to make this claim. However, recent research by mortgage provider ING Direct showed solar panels were the number one non-essential item in clinching house sales. Solar came above weekly bin collections and walk-in wardrobes! Installing solar PV badly is unlikely to help the value of your home. See our solar expert Ray Noble’s gallery of shame (right) for examples of how NOT to install solar pv.

WHAT IS BETTER, ‘FREE’ SOLAR OR BUYING THE SYSTEM MYSELF?
There are a number of ‘free’ schemes on offer where you pay nothing to have solar installed and the installer claims the Feed-In Tariff. The benefit you get is the free power during daylight hours. Because solar offers good returns we would recommend that you install solar yourself if you can. But if you cannot afford to do this a free scheme may be for you, but it will make the most economic sense to you if you are at home during the day time.

I CAN’T AFFORD TO BUY SOLAR OUTRIGHT. WHAT HELP IS THERE?
As above, free schemes or the Green Deal may be able to help you. If you cannot afford a whole system, or if you like the idea of clubbing together with like-minded people, there is now exciting growth in community solar. This means you could have a share in a much larger local solar scheme. Often these community schemes will offer a fair rate of return but invest a chunk of the profits locally for wider community benefit. See the resources section for organisations to contact if you are interested in community solar.

 

 

 

 

 

If solar were installed on all the UK’s south facing roofs & facades it would meet around a third of UK electricity demand.
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