What you need to know to install solar PV in your house

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Published: August 2011

Introduction: Household scale installations of Solar PV 

This article was updated in Janauary 2012.  It assumes that most people looking at solar PV projects will base their returns on the new tariffs.  At this time there is considerable uncertainty on the introduction date of the new tariff - see our blog post for more.

This article assumes a basic level of knowledge, in this case about Solar Photo-Voltaic (PV) systems and the Feed-in Tariff (FiT).  If you'd like to get up to speed on these areas before reading this then a good first point of call is the Energy Saving Trust site, specifically their Introduction to Solar PV and their Introduction to Feed-in Tariffs.  The current FiT rates are on the OfGem site although these are currently under review and lower rates for domestic scale solar PV projects are predicted from April 2012 onwards.

We also recommend that you also review our other articles in the Solar PV series:

Other consumer sites offer useful additional information on PV installation projects and we have included links to these at the bottom of this article. 

The number of domestic scale solar PV solutions is rising fast.  We have put together this article for those who are thinking about adding to this number.  It is based on first hand interviews with consumers who have undertaken projects together with discussions with PV installers.

Your investment in solar PV should ideally be part of a wider energy efficiency strategy in your home including how much you use, when you use it and the potential to make significant reductions through simple measures.  So before you spend £8,000 - 15,000 on a PV system you might find this is better spent making energy efficiency improvements to windows, doors, walls, attic, central heating (eg. new more efficient boiler) etc.  Making these improvements may well be cheaper and generate substantial savings.  You should also read our article "Energy Saving - First thing's first".

If you decide to progress a solar PV project you should consider how much of your electricity consumption could be shifted from hours of darkness to hours of daylight.  The more electricity you can use during daylight hours that then reduces your demand outside of this time the better.  This will generate significant additional savings on your energy bill.   

What options do I have for a PV project?

There are a number of alternative options for implementing solar PV on your property.  They include:

  • Buying a solar PV solution yourself with your own savings
  • Buying a solar PV solution with a loan (or with a significant contribution from a loan plus savings)
  • A ‘rent-a-roof’ scheme where you lease space on your property to a third party company to install solar PV

You cannot claim the FiT payments if:

  • You use an installer who is not MCS certified.
  • You use second hand kit – it must be new and MCS certified
  • You source the kit and find someone to install it for you – nice as it sounds, MCS certified companies won’t work this way.

Option 1: Buying a solar PV solution with your own savings

This option has the capacity to offer significantly greater returns but carries higher risk.  It suits people with savings of between £8,000 and £15,000 depending on the size of system they want to install.  If you don’t have these savings or you don’t want to lock up your savings for 8-10 years then you should consider a loan (see below).

Option 2: Buying a solar PV solution with a loan

This option has approximately 25% less overall profit after 25 years and the pack-back period is approximately 3 years longer compared with funding it yourself - once new tariffs, currently under discussion in February 2012, are finalised these figures would have to be checked.  However annual returns are still competitive (based on current interest rates).  A loan-based approach has the advantage that it doesn’t tie up your savings which could be invested elsewhere.  The loan repayments are also controllable with the majority being payable from the FiT revenue.  There are also mortgage lenders that will allow you to extend your mortgage to cover the cost of installing solar PV.  This option should also be considered.  See our article “Is Solar PV a sound financial investment?” for more on this.

Option 3: Installing solar PV through a ‘rent-a-roof’ scheme

These are now schemes where you enter into a 25 year contract to lease out an area of your roof to a third party company to install solar PV.  You often have to have a decent area of roof space (like 15+ square metres) to qualify.  As examples (we don't endorse any of them in any way) see www.freetricity.netwww.ashadegreener.co.ukwww.homesun.com or www.freeelectricity4u.co.uk.  Some of the major energy suppliers also offer their own schemes [though since December 2011 some have disappeared] although they often use third parties (like The Mark Group in the case of Eon) to do the installation.  This approach may be worth considering if: (1) you can’t afford the up-front cost of buying the kit; (2) you don’t want to take out a loan; and (3) you are likely to consume electricity during day-light hours (eg. through a full-time home office). 

However you need to take care going down a 'rent-a-roof' route.  There are a number of different models being used. There is widespread variation in terms and conditions – the ‘small print’.  The costs of installation, connection and on-going maintenance of rent-a-roof schemes should all be covered by the supplier.    Additional 'extra costs' for installation should be chargable only in exceptional circumstances.  Companies should be MCS certified and use MCS certified products.  They will often include free or discounted electricity to the ‘host household’ – your savings from this will depend on how much electricity you consume during daylight hours - for households around during the day this could be up to 30%, for those that are not it may be more like 10%.  It is highly unlikely to be anywhere close to meeting 50% of your energy needs (which some suggest)!!

If considering such a rent-a-roof approach you should compare offerings from multiple companies including reviewing, in detail, the terms and conditions linked to the offer.  We have not tracked down anywhere that offers a definitive list of companies offering 'rent-a-roof' solutions.  We would suggest anyone seeking this approach should get independent legal advice to review the terms of any contract.  This legal advice should be considered as an additional cost for this approach.   We also recommend talking to your home insurance provider about this type of solution.

If it’s possible you may move house over the 25 year period the 'standard' approach for 'rent-a-roof' schemes would be to pass the contract on automatically to the new owner.  So you need to consider what a potential buyer might think about taking over this contract from you.  They may even have an issue with the look of the panels or the space they take up?  They should, of course, quite like the idea of lower priced or free daytime electricity.  There are deals now where companies will come and take away the panels if that’s what you decide to you want at any point – we suspect there are some hefty exit fees for doing this.

There is more information specifically about 'Rent-a-Roof' schemes on the Energy Saving Trust site and also on the REAL Assurance site.  There's also an article on the Guardian site.  If you're interested in this option definitely read these.  The rest of this article focuses primarily on purchasing the solar PV kit up-front.

What can I do to research my options?

If you are intending to buy a solution up-front either with your own savings or with a loan then we recommend  reviewing multiple scenarios with an online ‘solar calculator’ to get an idea of project sizes (measured in kWp), up-front costs and potential returns.  There are many solar calculators online but we would recommend the Solar Guide calculator at www.solarguide.co.uk/solar-pv-calculator because it allows you to control your location and it offers you flexibility to change the default settings.

We would suggest you change the default settings on this calculator for:

  • Annual rate of increase in the price of electricity: 3% (this is much more conservative than the default 9% and closer to current UK Government projections)
  • Lifetime of the inverter: 12 years  (this means it builds in replacement costs for your inverter over the 25 year period)
  • Change the proportion of energy generated that you actually consume to a more conservative 15-20% which is far more likely - the maximum people are likely to use is around 30-35% through changes in behaviour, life-style, automated switching devices etc.
  • If you are not retrofitting your solution to an existing building then you need to change this setting
  • If you know your roof or panel angle then you should revise the 35 degree default setting
  • If you want to estimate your returns after 15 or 20 years (for example you want to assess the profitability after 15 years, or you think you'll move house in 15 years time) then you can change the duration of the project.

Assuming a system will run for 25 years with no maintenance is unrealistic.   We would suggest an additional £500-1000 is added to your overall project costs to cover on-going maintenance tasks over the 25 year period.  We also suggest you check with your home insurance provider as to the cover for your system – many home insurance providers do include cover in their existing policies but it's worth checking.  Unless you take out additional specialist cover it’s very unlikely to cover you for losses incurred as a result of ‘downtime’.

You should also talk to your mortgage provider to make sure there are no issues with a solar PV installation.

Does it matter where the property is located in the UK?

Yes, for example we estimate your returns could be 12% less if you are in Glasgow compared with Bristol (one of the sunniest cities in the UK being in the South West of England).  Returns in the South East may be nearer 1-2% less than Bristol, in Manchester they may be nearer 7% less.  Here's a graph of estimated outputs for these areas for a typical PV installation over 12 months based on PVGIS figures.  Your online solar PV calculator should take into account geographic variations in solar irradiance.

Solar PV estimated output for different UK areas

How can I start to design my solution?

Here are some suggestions for how you can do some of the groundwork yourself before an installer comes round to do a survey of your property.

Obviously the property needs to be owned by you to claim the FiT payments – if not then you will need to discuss the option with the owner.

You need to identify a suitable site and there are a number of factors to consider.  Are you looking at ‘retro-fit’ or ‘new build’?  Your FiT tariff will be different in each case.  Most people are putting panels onto an existing roof but if you are dealing with a new build situation there are other considerations.  You can design your system more freely around the available space on your roof.  Also for new build situations you should consider whether PV tiles are an alternative option – see our article on Building Integrated Photo-Voltaics (BIPVs)

Whether 'retro-fit' or 'new build' you can ‘roof-mount’ or ‘ground-mount’ panels – the FiT tariffs are identical for both these options. 

If you are putting panels on your roof then make sure it doesn't limit you (or even future owners of your property) to do an attic conversion at some point in the future!  Attic conversions are relatively popular and financially lucrative so you don't want to limit the potential of your house for expansion.

Your roof needs to be strong enough to take the extra weight of panels – most roofs will be but if in doubt consult a structural engineer.  Your roof should be sound and robust (and ideally less than 30 years old) – if it’s made up of more traditional building materials like clay tiles or slates that have been there for many years then there could be issues if there’s a problem with a section of your roof that's been covered with PV panels.  This may lead to a more expensive roof repair (see article on roof leaks).

If you are putting your panels on fixed-axis ground mounts these are usually secured permanently into the ground. This is usually a solution considered by people with larger gardens or land so they don't consume a significant proportion of space.  However there may be security issues with the panels you want to consider considering their value and easier accessibility.  There may also be issues with potential damage – even from garden ball games.  Shade, or the possibility of shade over the next 25 years, may also be a bigger issue.  Putting them somewhere unshaded that is out-of-the-way, perhaps not obviously visible to all, would be sensible.  You will need to run a cable sunk into a trench from your installation to the location of the inverter.

Solar PV should not require planning permission in England with the exception of Listed Buildings. Elsewhere in GB there it may if you live in a Conservation Area.  If in doubt check with your local planning department but, if they refuse on planning grounds, you should appeal as there are increasing numbers of these projects in more sensitive areas.

Whether roof-mounted or ground-mounted try to avoid shading at all costs.  Find a permanently unshaded spot.  You need to think not just about now but over the next 25 years.  You need to be careful to consider siting in areas where you might not have control over trees.  If shade could be caused by the growth of a tree in a neighbouring garden over the next 10 years and you can’t control it then this could be a ‘show-stopper’.   Experts say that shading can have a significant negative impact that is disproportionate to the area that is, even occasionally, shaded.

To maximise your yield you ideally want a south facing surface tilted at an angle of 30-40 degrees.  However you can still get 95% of the potential yield from a SW or SE facing panel tilted at 30 degrees and 90% from a SW or SE facing panel at anywhere between 10 and 40 degrees.  There are a large number of successful projects where panels are not facing due south and tilted at an angle of 35 degrees.

How large should my installation be?

PV panels in multiple patchesThis is the sort of issue you would discuss with potential installers but you can get a pretty good idea through your own research. 

In terms of space you should be looking for a minimum of 10 square metres to make the investment more financially sound.  Bear in mind you can have multiple ‘patches’ of PV panels (see photo).

There are multiple ways to look at sizing a system:

  • Do you have a limited amount of space?  Hopefully between 10 and 30 square metres.  Bear in mind that panels do not have to sit right next to each other – you can have multiple ‘patches’ of panels across your roof depending on available area.
  • Do you want to maximise your financial returns?  You will maximise your returns by picking the ‘FiT sweet-spot’ at 4 kWp capacity (for 'retro-fit' not 'new build' - see below) – this is the top limit of the FiT band with the highest payments and will usually cover about 30 square metres of space.  Smaller systems are proportionally almost as lucrative – most people don’t have 30 square metres of space, they have more like 15-20 square metres.
  • Do you want to maximise the amount of energy you generate?  If you have unlimited space then a 4 kWp system is optimal although you can obviously go larger if you don’t mind dropping down to the next FiT band - try out different scenarios using the solar PV calculators.  If you have 40-50 square metres available you should probably still opt for a 4 kWp system.
  • Do you want to offset your own electricity consumption so you are generating as much as you use?  This is a sound way to size your system and ensures that it is appropriate to your usage.  Using your electricity bills you can work out how much you consume on average each year and then size a system to offset this.  The solar calculator at www.solarguide.co.uk/solar-pv-calculator  allows you to size a system based on output.
  • Do you have a fairly fixed budget that defines how many panels you can purchase?  You may want to size the system based on what you can afford. Again the solar calculator above lets you size your system based on budget.  Currently the cheapest options are around £6,000 for an area of panels about 10 square metres in size.

Depending on your area available, you may want to pick a make and model of panel (or ‘module’) that covers the maximum amount of area.  Modules come in a range of sizes and it important to pick a make and model that fills the maximum area you have available.  You should discuss options with your installer.  Your installer should be able to offer you a range of options from different module manufacturers.

Should I be thinking about a solar hot water solution as well?

In a word, yes.  Solar hot water systems are about twice as efficient as solar PV in turning solar energy into usable energy (hot water).  They are also cheaper and take up much less roof space.  So, for many reasons, you should definitely consider them.

With the introduction of incentives for solar hot water systems (through the Renewable Heat Incentive or 'RHI') now being introduced from Summer 2013 onwards the case is further strengthened.  Keep a look out on the RHI section of our Forum for the latest news.

For those with more than 30 square metres of roof space you could do a 4 kWp PV solution AND a solar hot water solution.  For those with less roof space then rather than covering all your available roof in solar PV, you should consider sharing the space with a solar thermal system to benefit from the RHI.  Although we don't yet know the specific conditions from the Government, provided your house is relatively energy efficient, you can put solar thermal on your house now and it should qualify for the RHI when it arrives in October 2012.  If it is an older, more draughty house then it may be better to wait until the Government releases more information - this may be sometime between now and summer 2012?!

The ideal scenario is to do both provided you still have at least 10 square metres for your solar PV.  In terms of costs there may not be too much difference between the cost of a larger PV solution or a smaller PV solution and a solar thermal solution although this will depend on specific circumstances such as whether your hot water system can take a feed from a separate hot water source.

There are also hybrid Solar PV / Solar Thermal solutions on the market that do both. See for example http://www.newformenergy.com/hybrid-solar-solution which is MCS accredited and therefore enables you to claim the Feed-in Tariff. 

Could I put solar PV panels on my garage roof as well as my house?

Yes you can and this is a good idea if you don’t have enough roof space on your house but you have more on another building. The costs of installation are likely to be higher given it’s going to be more cabling and extra work for the installer.  However unless you have a separate metering point for your external building the regulator will view it as a single system for FiT registration.  So you can’t have a 3 kWp system on your house and a 2 kWp system on your garage roof and treat them as two separate FiT registrations unless, as we understand, you have separate meter points.  If you are considering multiple installations then we’d suggest talking to your installer and maybe also OfGem (http://www.ofgem.gov.uk/Consumers/Pages/Consumer.aspx) about this.

Can I do a project in stages – a bit now and a bit later?

Yes, there should be no technical problems with adding additional panels to an existing system at a later date although you would not want to exceed the 4 kWp threshold overall unless you were developing a much larger system.  It would be worth telling your installer that your intention is to extend the scheme over time as they may specify a more expensive, higher spec inverter if that’s the case.  Overall, to do them separately, will cost you more as the installer will have to come back and install additional modules, connections etc.

This could be an effective way to manage a project in line with your finances.  If you have enough savings now to do 10 square metres, then in 2 years time do another 10.  You would have to weigh the extra costs of doing it this way over using a loan to do a 20 square metre system from day one.  It could depend on your attitude to taking out loans.

It you did split system development into chunks there could be timing issues.  What happens if the tariff levels change after the first half of the job?  We suspect that your final solution would be registered twice and your payments would be based on two different tariff levels.

Any issues with doing a solar PV project on my holiday house?

No, you can install PV on your second (or even third!) home and they will be treated as completely separate registrations.  However the ‘tax-free’ benefit from FiT are only applicable to your primary residence as a domestic solution.  This would be classed as a commercial registration so you will be liable to pay tax on FiT revenues on second homes.

See comment at the bottom of this article which suggests that the rules have changed on this.

Does it matter which company currently supplies my electricity?

In theory ‘no’ because they all support the FiT scheme and you should be able to register your FiT application with a different company to the one that supplies your electricity. 

In practice some are a great deal better at making the FiT registration process quick and easy than others.  We have talked to a number of customers who have been very frustrated with the service they have received to get their projects registered.  Once this has happened they have generally been happy – the cheques just arrive every quarter.

In practice many people register their FiT project with their current electricity supplier.   However there is no reason why you can't use an alternative  energy supplier to register your FiT application even if you wanted to keep your current electricity supplier.

How do I find a reputable installer?

It’s an obvious point but talking to others (both online and in person) that have done it is one of the best ways to give you the confidence to make what is likely to be a significant investment.

You must use an installer that is certified under the Microgeneration Certification Scheme (MCS) in order to benefit from the FiT.  The Renewable Energy Assurance Limited (REAL) scheme defines a code of conduct which all MCS members must follow.  This is intended to ensure that consumers are not faced with high pressure selling techniques and significant discounts.

You should seek quotes from at least 3 potential MCS certified installers.  We suggest you select at least one smaller local company and at least one regional or national player – there are pros ansd cons with each.  It’s likely that the regional or national company may be more expensive but they might provide a more robust, rounded service and be better able to offer support and maintenance cover over the next 25 years.  Conversely smaller local installers make the point that their long-term reputation in the neighbourhood is going to be far more crucial to their business than a regional or national provider – so they are more likely to offer better customer service and, due to their lower overheads, more competitive pricing. 

There are a significant number of places you can go online to find your nearest local installers by entering your postcode.  We would suggest you use the MCS tool (see http://www.microgenerationcertification.org/mcs-consumer/installer-search.php) which will ensure you get access the most comprehensive and up-to-date list of all companies that have MCS accreditation.   This also lists date of certification so you can get an indication of whether the company has only recently started offering this service or whether they’ve been involved from the start in 2009.

Finding reputable national or regional scale installers is not easy using the MCS tool.  Many of the search tools don’t handle this distinction well.  In the case of the MCS one, if you omit your postcode then you get a list of everything – then use the tabs across the top to narrow down your search to a region.  But picking from a list of over 1000 companies in each case doesn’t help much!  Another search tool is on the REAL site – most installers will be REAL members.  But again if you subset this by ‘Nationwide’ you generate 700 members related to solar PV.  The problem is that installers self-register themselves and are free to tick whatever ‘geographic market’ boxes they like.  Hence many will not want to limit their appeal.  Another small list of larger installers is on the Good Energy site - SolarCentury is on this list.  They were one of the first UK companies offering solar PV solutions and are also GEN Supporters.

Many of the ‘big six’ energy companies now offer home PV installation services although we would advise you check first whether they are using their own staff or simply passing work on to the same local installers you could go to directly yourself.  As an example, here are the solar offerings from SSE.

When you contact a prospective installer you can provide them with useful information at this stage, for example what you are seeking to achieve from your solution?  In some cases they are likely to visit your property.  Ideally you don’t want a ‘sales chat’, you want a technical survey.  Some may try to get you to email information through and supply a quote based on this information without an on-site visit. It depends how much you trust them if you can’t get them to do an on-site visit!

What questions should I ask a prospective installer?

Here’s a checklist you could ask or email them:

  • How long has the company been operational?
  • How many full-time employees do you have doing installations?  (This gives you an indication as to whether they will do it themselves or sub-contract the install to a third party)
  • How long have you been doing installations of solar PV?
  • How many domestic solar PV installations have you done?
  • Can you provide some contact details for your customers in my area so I can get references?
  • Would you do an on-site survey before offering a quote?
  • What manufacturers of solar PV module do you support?
  • Which manufacturer do you generally recommend and why?
  • Roughly how do your customers break down in terms of percentage by different module manufacturer?
  • Do you employ all your own installation staff or use sub-contractors?
  • Can you send me copies of typical warranties you offer on (1) different solar PV modules (2) different inverters (3) the installation work?
  • Can you send me a typical quote for a similar sized job?
  • Do you have standard company terms and conditions you can send?
  • When would you be able to do the work?
  • How many days would you expect the installation to take?

Experience over many projects of course provides a lot of re-assurance.  There are a lot of new entrants into the market – they don’t need to be experienced to be MCS certified!  Companies that have completed a significant number of installations and can provide references for other satisfied customers in the area are likely to be lower risk.  The REAL code of conduct they are obliged to sign up to means they have to abide by certain conditions – this includes pressure selling and significant price discounting.  However you will find prices vary significantly due to the ability of installers to cut their margins on the technology they are re-selling and the day rates for installation.  Typical margins on the cost of the panels are around 25-30% based on wholesale prices.

Who is actually going to do the work on your property and how much experience do they have? 

You should also ask your installer what makes and models of PV module they support.  Almost every installer we’ve talked to has a watertight set of reasons why the ones he uses are the best on the market!  He should be able to offer you a choice – this may be between a Chinese manufactured panel and a European manufactured one.  You can guess which will be pricier!  See below for more on choosing your panel manufacturer.

Call your potential installer unexpectedly and see what sort of phone support service they offer.  How quickly can they respond to something?  Many are extremely stretched right now in terms of resources and may not get back to you promptly.

Given the time constraints, find out when your installer can do the job – be aware of current tariff deadlines.

In some cases an installer will be happy to do a site visit – ideally this would include a technical survey before offering you a quote for the complete installation.  The quote should cover:

  • Whether you have a suitable site
  • What size in terms of area and output best suits you
  • Where you should site your inverter and any other installation issues
  • Installation costs
  • Length of pack-back in years
  • Anticipated profit after 25 years

If you have used the online solar calculators you will know most of these figures already.  All installers have to use the same government agreed methodology to do these calculations.  Many installers will tell you they are overly conservative and your panels should generate more than these calculations predict.  This is true.

The key ‘unknown’ in all these predictions is the area of savings – no-one knows for sure exactly how much electricity prices are going to rise over the next 25 years.  Expert opinion suggests they will rise but is divided in terms of the scale and rate of rise.  The size and rate of increase will impact directly on your potential to make savings.  The higher prices rise the more potential you have to generate bigger savings.

Their quoted costs should break down:

  • All kit including potential options for make/model of PV modules, make/model of inverter, cabling etc.
  • Scaffolding hire costs
  • Time/labour costs for installation and connection
  • Warranty on installation plus company terms and conditions
  • Optional maintenance services from the installer
  • Optional technology for remote monitoring (you can monitor generation levels through online tools)
  • Optional warranty on inverter

We would suggest you ask all installers whether the staff they use are actually employed by them or whether the use external contractors.  It’s perfectly legal for companies that are MCS accredited to use contractors to install their solutions that are not – the solution is still MCS accredited because it is covered by the accreditation of the lead contractor.  However we would suggest that the chain of responsibility is less complex if you use a company that employs its own staff to do installations.

How do I select a PV panel make and model?

Does it matter which make and model I chose?  Our advice, as a result of talking to those in the sector, is that it does matter but not for performance or yield reasons.  The difference between the best and the rest for most modern PV panels (whether crystalline or thin film) is not sufficiently big to make any real difference in terms of financial return, even over a 25 year period. 

Experts suggest you should use a manufacturer that has been making solar PV modules for many years and is likely to have a fairly refined, trusted product.  There are a range of European manufacturers supplying products globally and global companies with UK based divisions like Sharp that have PV production plants based in the UK. Here’s a list of the global top 10 solar PV manufacturers. Independent testing does take place - see an example of a recent test for 13 leading manufacturers by TUV Rheinland (although we cannot find any published report from this test).

It is also vital to take into account the potential longevity of your manufacturer - will they still be around in 25 years time?  You should get a 25 year warranty for your PV modules, a contract between yourself, the customer, and the manufacturer to cover any problems.  These do occur occasionally where specific modules malfunction and do not operate at their maximum capacity.  So it is important to source your modules from a manufacturer that is going to be around for the next 25 years and is relatively easy to contact.

If you want to source panels from more ethically sound companies then it’s worth reading this Guardian article.

Will these panels really last 25 years and deliver what they claim?

Solar PV panels have no moving parts making them a lot more robust than many other bits of kit. If they do malfunction then one or more of the modules may not operate at their maximum efficiency although you’ll need to keep an eye on your average generation statistics to know this!  Some installers will offer you a remote monitoring device that allows you to monitor your generation performance using an Internet based dashboard from anywhere with an Internet connection.

Over a 25 year period efficiency loss is likely although there are things you can do to your panels to maintain them and minimise this annually. The solar calculator we prefer (http://www.solarguide.co.uk/solar-pv-calculator) builds in an efficiency loss over the 25 years so that, by the end of the period, they are only 80% as efficient as when they were new.

Also bear in mind that Germany is close to 10 years ahead of us in terms of domestic promotion of solar PV and they have a huge number of installations based on the same technology. They also have large test centres doing independent PV module performance testing (see TUV Rheinland for example).

How should I pay for the system?

When it comes to up-front payments keep these to less than 25% of the total price.  The remainder could be split into two with 50% being paid on completion of the work and the remaining 25% after a period of effective operation.  There’s useful guidance around contractual details on the REAL Assurance site.

How long does it take to install the whole system?

Not long - usually between 1 and 2 days to do everything and there is minimal disruption to other parts of the property.  You do need a bit of space, often near your electricity meter, for the inverter – a box that can be wall-mounted about the size of large shoe-box.  Chack with your installer as to where best this should be sited.

Your installer should also help you to complete the FiT registration paper-work that gets sent off to MCS and OfGem, the industry regulator, who monitor all registrations across the UK.  There’s more about the registration process at https://certificate.microgenerationcertification.org/default.aspx.

What problems might arise and is there anything I can do?

Problems can occur - see this article about a rise in leaky roofs as a result of roof mounted renewable kit for example.  If you have issues with your installer you can provide details of problems to the REAL Assurance Scheme at http://www.realassurance.org.uk/consumers (tel. 020 7981 0850).

What about on-going maintenance?

You need to monitor the output from your panels in some way so that any problems will get picked up.  We've talked to a people using different options:

(a) Traditional pen and paper to maintain a form recording outputs once or twice a day

(b) A digital data logger like the http://www.theowl.com/index.php?page=owl-usb which allows you to connect it to a computer and download historical data to store and analyse.  We suggest this might be the least hassle route for lowest cost.

(c) A more sophisticated wireless system that not only allows you to track your PV system performance from any device anywhere that has Internet access but could also allow your panel manufacturer to monitor the performance of your system and make sure it is in line with other systems they've got in the area.

To check your system outputs are equivalent to others in your area you can upload your data to sites like http://pvoutput.org/ or http://www.bdpv.fr/index_en.php.  These allow you to compare your data with others.

It is certainly possible that you will need to replace your inverter over the lifetime of the project.  Engineers say these do malfunction although it is possible they could continue to function well for 25 years.  A conservative approach would be to include something like an extra £800-1000 in your budget to replace your inverter.  Alternatively take out a 25 year warranty on the inverter – this should be optionally available from your installer although it will be between you and the manufacturer of the inverter.

It is sensible to have the panels cleaned occasionally.  If you get heavy prolonged snowfall then it might be sensible to consider shifting the snow to reduce weight.  Depending on your panel location, both jobs may not be easy!  The panels are designed to be self-cleaning provided they are installed at a suitable angle.  Ian at SolarCentury comments on the Discussion forum:

When solar panels are installed correctly, on a suitable roof pitch, normal precipitation should keep them free from the worst dirt and dust. In very polluted areas you may benefit from having the panels cleaned, using a mild detergent and water. The panels should always be cleaned from the ridge down, to avoid spraying water up the roof and under your roof tiles or slates. Modern cleaning companies who use ground based cleaning equipment, where access to the roof can be avoided, would be the best approach.

If surrounding trees or other vegetation start to cause shade then you will need to trim these back.

To optimise my system should I be thinking of anything else?

You want to try and change your household behaviour wherever possible to move your electricity consumption from hours of darkness to daylight especially in the period from Spring to Autumn.  Many of your appliances like washing machines and dishwashers will already have timers that allow you to load them up but they then switch themselves on automatically during the day.  You can buy simple plug-in timers to control power to applicances - this is an example of a 7 day one if you have different routines during the week compared with weekends.

Where possible do tasks you have more control over on 'good generation days' like ironing, washing, tumble-drying, charging up appliances (mobile phones, toothbrishes, laptops) etc.

Solar PV is a more effective solution when combined with other renewable technologies like ground source or air source heat pumps.  These consume electricity for operation although the net energy gain (in terms of heat they can generate) is significantly higher than the power they consume.

Is timing important?

Timing is important and you need to be aware of the latest deadlines imposed by the Government for Solar PV FiT tariffs.  Bear in mind the deadlines are for registration of your system with OfGem through your FiT supplier.  Your project needs to be fully completed in advance of any deadline.

Other useful online resources

Which? article on How to Buy Solar Panels  http://www.which.co.uk/environment-and-saving-energy/energy/guides/how-to-buy-solar-panels/how-to-buy-solar-photovoltaics/

Energy Saving Trust Renewables Buyers Guide

Microgeneration Certification Scheme Consumer pages  http://www.microgenerationcertification.org/consumer

REAL Assurance Consumer Guide http://www.realassurance.org.uk/pdf/consumer-guide.pdf

Micropower Council’s Golden Rules http://www.micropower.co.uk/sites/default/files/uploads/files/Microgen%20Golden%20Rules.pdf

OfGem Feed-in Tariff Scheme  http://www.ofgem.gov.uk/Sustainability/Environment/fits/Pages/fits.aspx


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A very comprehensive article,

A very comprehensive article, indeed! There is a lot of information to take in, but something that was only mentioned in passing is the impact on insurance...


Would having solar PV require informing my insurer? If so, would it be likely to increase my policy? What would the main hazard be?

Tax exemption of FiTs on second homes

Disagree with your point on tax and pv on holiday homes. HMRC have changed their advice on this recently.

At http://www.hmrc.gov.uk/manuals/bimmanual/BIM40520.htm they say:

"The exemption may apply where an individual installs a microgeneration system at a property which is not the individual’s main residence provided that the other domestic property is used by the individual, wholly or mainly, as a separate private dwelling and the other conditions for the exemption are met."

If the other property is mainly rented out then I don't think the exemption will apply but if the holiday home is mainly used by the owner then it should.

First of all: Thanks for

First of all: Thanks for putting all this together in one article. Really comprehensive! I think that halving of the subsidy rate ist painful for some installers and some prospect clients but nevertheless necessary. The german market is a good example: the feed-in tariffs were cut several times and the demand is still on a high level due to decreasing prices and more efficient panels.