solar guide p1

8/14/2019 Solar Guide P1

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To find out more aboutinstalling solar electricitypanels call 0300 123 1234 or

visit energysavingtrust.org.uk


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07 A buyers guide to solar electricity02

Energy from the sunThe sun provides an abundant, free source ofclean energy in the form of natural light andwarmth. It is possible to capture some of thisfree energy directly to convert sunlight intoelectricity using solar photovoltaic (PV) panels.If youre thinking about installing solar PV togenerate electricity this guide is for you.

How does solar PV work?Solar PV systems convert light into electricalpower using a thin layer of semi-conductingmaterial, usually silicon, encased between asheet of glass and a polymer resin. Theyrange in size from a few square centimetres,for example on calculators and watches to

systems of hundreds of square metres madefrom interconnected modules that form anarray. When exposed to daylight electronsin the semi-conducting material becomeenergised. These electrons are then ableto flow through the material generating adirect current (DC). The DC is carried throughwiring to an inverter which converts thecurrent to 240V alternating current (AC)

so it can be connected to your homesmain electricity supply.

What does kWp andkWh mean?Solar electricity systems are given arating in kilowatts peak (kWp). This is

essentially the rate at which it generatesenergy at peak performance for exampleat noon on a sunny day. The kWp of adomestic system will vary depending on howmuch a customer wants to spend and theroof area available to accommodate thepanels.

The total amount of electricity the systemactually generates in a year is measuredin kilowatt hours (kWh). This will dependon the systems orientation, shading andhow sunny your site is, as well as thesize of the system (in kWp) that you haveinstalled.

A typical domestic system is between1.5 and 4kWp. Each kWp should generatearound 800 to 850kWh per year if unshaded

and facing due south with a tilt of around30-50. A solar roof array would typicallygenerate 1200 to 3400kWh per yeardepending on size.

By contrast an average home uses4400kWh of electricity per year on lightsand appliances. However, an energy efficienthome using A rated appliances and lightingcould conceivably use half this value.

Effortless integrationSolar PV can be easily incorporated into mosthouses. The most common option is to usestandard solar PV modules in a frame fixed toan existing pitched roof or a tilted frame on a

To find out more callfree on 0300 123 1234.


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A buyers guide to solar electricity 03

flat roof. In this arrangement the panels willslightly protrude from the roof tiles but arestill in keeping with the shape of the house.If you are replacing your roof you can buysolar PV integrated roof tiles and slates thatcan form part of the weatherproof membrane

or structure.VersatilityAs solar PV is made up of modules, typicallyaround 1m x 1.5m, an array (the full solar PVinstallation) can be designed to accommodatevirtually any size and shape of roof. Solar PVcan also be mounted vertically and horizontallyallowing the system to form part of the walland roof structures in new properties althoughperformance will be reduced with theselocations.

Orientation and tiltYour roof should ideally face due south at apitched angle of between 30 and 50 from thehorizontal to give the best overall annual

performance. Installations facing anywhereto the south of due east and due west arefeasible, although output will be reduced.Installation is not recommended on roofsfacing north.

This table shows the percentage variance in performance when orientation and tilt are adjustedaway from the optimum (100%).

- - - - - - - - -

90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 90

0 87 88 90 91 92 92 93 93 93 93 93 93 92 92 91 90 89 87 86

10 84 87 90 92 94 95 95 96 96 97 97 96 95 94 93 91 89 87 84

20 82 85 90 93 94 96 97 98 99 99 98 97 96 95 93 91 88 84 81

30 78 83 87 91 93 96 97 98 99 100 98 97 96 95 93 89 85 81 78

40 75 79 84 87 92 94 95 96 96 96 96 95 94 92 90 86 82 77 72

50 70 74 79 83 87 90 91 93 94 94 94 93 91 88 83 80 76 73 70

60 65 69 73 77 80 83 86 87 87 87 88 87 85 82 78 74 71 67 63

70 59 63 66 70 72 75 78 79 79 79 79 79 78 75 72 68 64 61 56

80 50 56 60 64 66 68 69 70 71 72 72 71 70 67 66 60 57 54 50

90 41 49 54 58 59 60 61 61 63 65 65 63 62 59 60 52 50 47 44

West

TILT

deg

rees South East


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Shape of roof areaSolar PV arrays are made up of modulesof about 1.5m2which allows most availableroof shapes to be accommodated. TypicalUK installations are around 20m2. For examplea 3kWp system could comprise of 16 panelstaking up an area of 24m2 and will generateroughly 2500kWh per annum.

ShadingAny shading on a single module will affect theperformance of the whole array as all themodules are connected. A system can toleratesome shading early or late in the day without

much reduction of overall output but it shouldnot be shaded between 10am and 4pm.Nearby trees, chimneys, TV aerials and ventpipes are all common causes of shading andshould be accounted for before anyinstallation.

Solar electricity doesnt necessarily requiredirect sunlight and can still generate electricityon cloudy days. You will generate approximately1/3 of the energy on a cloudy day as on asunny day at the same time of year.

Seasonal performanceThe chart above shows a typical seasonalspread of energy generation for an averagesystem of 3kWp facing south. The wintermonths generate significantly less electricitycompared to the summer months.

Site locationThe amount of electricity generated by asolar PV system can also vary depending onwhere you live in the UK. Northern areasreceive slightly less energy from the sun overthe year. For example a 1kWp system will

generate less electricity in Northern Scotlandthan it would in Cornwall. However solarelectricity is still worth while in the northernparts of the UK as the differences arentsubstantial.

You can get an estimate of how much asystem will generate in your location(and how much it will earn) using ourSolar Energy Calculator - energysavingtrust.

org.uk/solar-energy-calculator

Jan

Monthly energy generation in kWh

Feb March April May June July Aug Sep Oct Nov Dec

0

50

100

150

200

250

300

350

Energy generation by month 3kWp system


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Solar PV cell typesThere are several different types of solar PVwith different characteristics, costs and benefits.The main options for domestic use in theUK are:

Crystalline cellsThese are the most commonly manufacturedtype. There are performance variationsdepending on whether you opt for amonocrystalline cell (often the moreefficient of the two) or a mix of crystalsor polycrystalline cells which have amarble-like appearance. Polycrystallinecells can be cheaper to produce.

Hybrid cellsThese combine crystalline cells with anothercell type, thin film to give the best overallperformance. Hybrid panels often cost more tobuy than the other types. However, there aremany other factors that also affect the totalinstalled cost of a system.

Cell type Efficiencies* Approximate areaper kW(m2)

Monocrystalline 13-17% 6-8

Polycrystalline 11-15% 7-9

Hybrid 17%+ 5-6

* The efciency of a solar cell gives an indication of how much of the suns energy is actually used by thesystem per unit area. The higher the efciency, the better the cell is at converting the suns energy perunit area.


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Connecting to the gridThe vast majority of systems are installed inproperties with an existing mains electricitysupply. The solar PV supply feeds into yourexisting system and the electricity generatedis either used in your house or is exported tothe grid, depending on how much you areusing at the time. Connection to the local

grid is not as complicated as you mightexpect and your installer should be able todeal with this for you by informing theelectricity District Network Operator (DNO).

For isolated installations where there is nogrid connection, solar PV panels can be usedindependently by using batteries to ensuresupply when there is not enough daylight togenerate electricity or when you need more

energy than the system is able to generate.

Connection equipmentA basic grid-connected solar PV systemrequires no batteries. If the grid failshowever, for example in a severe storm -grid-connected inverters automatically switchoff to protect any engineers working on thelines to repair them. If grid related power cutsare common in your house you might considersome form of back-up storage. Consult yourinstaller for further details.

PermissionsIn England, Wales, Scotland and NorthernIreland changes to permitted developmentrights for domestic renewable technologiesmean that most solar electricity installations

dont generally require planning permission, aslong as they respect certain criteria.A key criterion is that the panels should notprotrude more than 200mm when installed.Particular exceptions apply for installations onflat roofs, listed buildings and buildings inconservation areas, world heritage sites and

designated landscape areas. We recommendyoualways check this with your local planning

department in advance of installation.Make sure you inform your building insurancecompany of your installation as they may needto note it as a material fact on your policy. Thisshouldnt increase your premiums but checkfirst with your insurance company. You mayneed to obtain approval from Building Control.This is to ensure that your installation doesnot compromise the buildings structure.

Photocourtesyofzedfactory.com

To find out more callfree on 0300 123 1234.


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of the package. You will need to show thatyour home has an Energy PerformanceCertificate rating of at least band D toqualify; if you cant achieve band D then yourFeed in Tariff rate will be 9p/kWh.

Until Smart Meters are rolled out across

the country any export payments through theFITs will be deemed at 50%. This means youwill get paid for exporting 50% of theelectricity you generate regardlessof how much you do actually export.

To be eligible for the full Feed-in Tariffspayments both the system and the installermust be registered under the

Microgeneration Certification Scheme(see How to find an installer).

Where possible it is recommended you useany appliances during the day when the solarPV modules are generating the electricity.This avoids the full cost of taking electricityfrom the local grid and makes maximumuse of your own investment in your solar PVsystem. Obviously you shouldnt use

additional electricity just to make use ofthe solar PV output.

Governments Feed-in Tariffs(FITs) and exporting electricityWith the UK Governments Feed-in Tariffs(FITs) scheme, you can get paid for theelectricity you generate with your solar PV

array. The scheme guarantees a minimumpayment for all electricity generated by thesystem (generation tariff), as well as anadditional payment for the electricity exportedto the grid (export tariff). These payments arein addition to the bill savings made by usingthe electricity generated on-site. The paymentsyou are eligible to receive vary depending on

system size and when it is installed. Thepayments are index linked and guaranteed for25 years.

For every unit of electricity generated youwill receive the generation tariff forsolar PV currently set at:

You will also be paid 3.2p/kWh for every unitof electricity you export and you will savearound 14.4p/kWh on your electricity billfor every generated unit that you use inyour home.

The amount of energy generated will bemeasured by an approved generationmeter, supplied by your installer as part

Technology Current Tariff

Scale tariff lifetimelevel (years)(p/kWh)

4kW (with EPC 21 25band D or higher)

4kW (with EPC 9 25

band E or lower)

Tariffs as of April 2012. For the latest tariffsplease visit www.energysavingtrust.org.uk


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Most of the above services will be required, soif they are excluded from your installersquote, you will need to obtain separateestimates or make your own arrangements.It is important to bear this in mind whencomparing quotations.

Most domestic solar PV arrays are between1.5kWp and 4kWp. A typical 3kWp system will

cost up to 10,000.Here is an example of what a typical domesticsolar electricity system with an installationsize of 3kWp could earn and save you eachyear through the Feed-in Tariffs:

Export tariff income is calculated on the basis

that 50% of the electricity generated isexported. The Feed-in Tariffs rates are indexlinked, so this income should hold its valueover the entire life of the system.

per year

Generation Tariff 530

Export Tariff 40Reduction in current electricity bills 100

Total savings and income generated 670

Based on a tariff rate of 21p/kWp, export rate of3.2p/kWh and electricity price of 14.4p/kWh. TheFeed-in Tariffs are not currently available in NorthernIreland.

Costs and savingsOn average (across cell types), solar PV costsup to 3,500 per kWp installed, though costsare continuing to come down. When comparingquotes from installers do not simply focus on

the suggested system capacity as this isprobably not the best way to compareperformance or cost effectiveness.When comparing prices ask the installerwhat is included. Some things are oftenexcluded from an initial estimate including:

Scaffolding (if required). Removal of the existing roof and other

roofing works. Any internal work to install wiring. Connection agreement with the Distribution

Network Operator (DNO).

Allowance for lightning protection. Electrical connection work (this requires

a fully qualified electrician).

A generation meter. Other display meters if required (i.e. handheld

display meter).


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MaintenanceVery little maintenance is required if awell-designed solar PV system is installedproperly. Modules that are tilted at 15 ormore have the additional benefit of being

cleaned by rainfall to ensure optimalperformance.

You can expect them to operate for 25 yearsor more before they need replacing, althoughthe inverter may need replacing twice over thelifetime of the panels. Once fitted, yourinstaller should leave written details of anymaintenance checks that you should carryout from time to time to ensure everything is

working properly. This should include detailsof the main inverter fault signals and keytrouble-shooting guidance. Ideally yourinstaller should demonstrate this to youat the point of handover.

In areas that experience high levels of dustand grime such as city or industrial locationsyour solar PV array may need additional

cleaning from time to time as rainfall maynot be sufficient. Consult with your installerfor exact maintenance requirements before youcommit to installing a solar PV system.

WarrantiesSystem warranties may vary: manufacturersperformance warranties on modern solar PVmodules typically last up to 25 years. Inverter

warranties can be as long as seven years.Installer warranties may be five years,although, two years is a minimum to cover theinstallation. If the system is a part of otherroofing work check with your roofingcontractor that the solar PV installation doesnot affect the roof warranty.

How to find installersand ProductsWhen you buy a renewable energy technology,there are currently two industry led andGovernment approved schemes that you

should check that your installer is a memberof. They are the Microgeneration CertificationScheme (MCS), and Renewable EnergyAssociation Ltd (REAL) Assurance scheme.

The MCS scheme will cover any technicalrelated issues while the REAL AssuranceScheme covers all contractual relateddisputes, including deposit protection andworkmanship guarantees. In addition, MCS

also certifies renewables products as so lookout for the MCS logo. We recommend gettingat least three quotes from installers beforeproceeding with any work.


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MicrogenerationCertification SchemeThe Microgeneration Certification Scheme (orMCS), exists to ensure that installers install tothe highest quality every time, using MCS

certified products that have met rigoroustesting standards. All MCS approved productswill come with a guarantee for a set period oftime, which your MCS approved installershould clearly explain to you. To check thatyour installer is MCS certified, you can searchfor them on the MCS website or call theEnergy Saving Trust for free advice on0300 123 1234. For more information aboutthe scheme, go to microgenerationcertification.org

REAL Assurance SchemeAll MCS-certified installers must belong to anOffice of Fair Trading-backed consumercode-of-conduct programme, and the REALAssurance Scheme is currently the only one

available. The scheme covers general businessstandards, such as protection against excessivedeposit payments and workmanship warranties,which installers must always explain toconsumers both in writing and verbally.

To check that your installer is a member ofthe REAL assurance scheme visitrealassurance.org.uk or call REAL on0207 981 0850.

Deposit and AdvancePayment Insurance SchemeAll REAL members must provide protection fordeposits and advance payments they takefrom domestic consumers. REAL membershave access to insurance known as theDeposit and Advance Payment Insurance

Scheme. The scheme is designed to provideprotection for payments made before workshave begun, just in case the company ceases

to trade before they deliver the goods to you.

The Deposit and Advance Payment InsuranceScheme has been arranged between REAL andthe insurance scheme administrator (QANW).You will not be asked to pay anything for theinsurance cover, either to the REAL Assurance

Scheme or to the company youre contractingwith. The company can register your contractwith the scheme administrator and you willreceive an insurance policy by post.

For further information on this scheme pleasevisit www.real.qanw.co.uk/consumer-faqs.php,or call 01292 268020.

Workmanship WarrantiesWhen you purchase a renewable energytechnology, your MCS installer is obliged toprovide a workmanship warranty for aminimum of one year. However, typicallyspeaking many companies offer warranties forlonger than this. Members of the REALAssurance Scheme are required to put in placearrangements to ensure that the warranty they

provide will be honoured if the companyceases to exist during the warranty period.Under the Deposit and Advance PaymentInsurance Scheme consumers are given theopportunity to purchase warranty insurance foran additional 35. This insurance providesprotection should the company cease to tradeand is valid for the period of the installersoriginal workmanship warranty. If the installer

company has not already provided aninsurance backed warranty the Energy SavingTrust recommends that you pay this additional35 for the workmanship warranty insurance.

For more information about this scheme visitreal.qanw.co.uk/consumer-IBG-faqs.php, or call


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Check list:Before making the decision to go ahead andinstall solar PV, we recommend that you usethe following check list:

I have checked my homes EPC rating toassess whether it is a band D or better.YES/NO

I have considered the available space for asolar PV array and inverter YES/NO

I have considered my current electricity useYES/NO

I have received at least three quotes(however, do not compare installers on costalone; the cheapest may not be the mostappropriate option for you) YES/NO

I have checked any proposed works withthe local authority planning and buildingcontrol teams YES/NO

I have chosen an MCS certified installer thatuses MCS certified products and is a member

of the REAL assurance scheme YES/NO

I have checked what warranties are on offer both product and workmanship, includingpost installation services YES/NO

I have checked that I have received abriefing from my installer on how to operateand perform basic maintenance checksYES/NO

01292 268020.

What should I expectfrom my installer?All MCS approved installers should be able toprovide a detailed breakdown of the

specification and costs of their proposedsystem. They should:

visit in person and complete a technicalsurvey before quotation

explain how they have calculated the sizeof the system to be appropriate forelectricity use, including calculationsfor system efficiency

comply with the lastest MCS MIS 3002standards

provide an estimate of how much electricitywill be produced by any proposed system

supply clear, easy to understand anddetailed information and advice on how bestto use the system and operating instructions

explain how the system will be installed andif there will be any disruption to your property install and set controls and settings to

ensure you get the most out of your system

provide clear and easy to understandinformation on product andworkmanship warranties

provide a full breakdown of costs in theirquote and include the terms and conditions not ask for more than a 25% deposit. You

also have the right to cancel the contractwithin seven days with no penalty

To help you make an informed decision wesuggest you get as much information aspossible from product and installer brochures,

which may include background information onperformance testing.

Call the Energy Saving Trust on0300 123 1234 for informationabout certified products andinstallers available in your area.


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Printed on Revive Silk which contains 75% de-inked post-consumer waste and a maximum of 25% mill broke

Energy Saving Trust

21 Dartmouth Street, London SW1H 9BP

Tel. 0300 123 1234 energysavingtrust.org.uk

EC320 Energy Saving Trust May 2012, E&OE.

To start generating your ownenergy visit

Energy Saving Trustenergysavingtrust.org.uk

Microgeneration Certification Schememicrogenerationcertification.org

REAL Assurance Schemerealassurance.org.uk

How the Energy SavingTrust can helpThe Energy Saving Trust is a non-profitorganisation providing free, impartial advice tohelp you stop wasting energy and money and

help fight climate change. To find out whatyou can do to generate your ownenergy visit energysavingtrust.org.uk orcall us free on 0300 123 1234.

Our advisors will:

Give you personalised advice on whatspractical for your home.

Put you in touch with local certifiedinstallers.

Tell you about grants and offers availablein your area.

Thanks to all the contributions from BRE, Gemserv,

Oxford University, REAL Assurance, Scottish and

Southern Energy and Solar Century.

All measure costs and savings are correct at time of

printing. However nancial savings will change as

energy prices rise or fall. Please refer to our website

for the most recent measure costs and savings.

solar guide p1

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