How to buy solar panels Solar PV installation

Chris Weatley solar panels after

3.5kWp PV system after installation (courtesy of Chris Wheatley)

We've filmed an installation of solar photovoltaic panels so you can see what to expect if you are considering buying solar panels. Plus, our experts answer your questions about whether your property is suitable for solar panels.

Installing solar panels

If the solar panels are to be installed on your roof, it's likely that you're going to need scaffolding erected for the installation. Make sure you check with the surveyor that there is space to install scaffolding and that the quote includes the cost of it. 

Once the scaffolding is up, the panels could be installed in less than a day. Roofers will attach the fixing brackets onto the rafters of your roof - this is why a proper surveyor should go into your loft to check the integrity of the roof and the rafters. The solar panels will then be clamped onto the fixing brackets.

The picture, above right, shows a Which? member's roof undergoing installation of a 3.5kWp PV system.

Video guide: solar PV installation

To get a better idea of what you can expect when installing solar PV, watch our video below to see a solar panel installation (on a concrete tiled roof) from start to finish, and find out what's involved.

 

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Video transcript

Are you thinking about installing solar PV panels? Producing your own electricity from solar is not only great for the environment, but it can also save money in the long term thanks to the feed-in tariff, and it can protect you from rising electricity bills.

But the decision
to install solar PV panels on your home is a big one.

It can be nerve-wracking when you've never seen how it's done. So we filmed a solar panel installation to show you what happens, and answer some of those common questions. But first, let's find out how the system works.

Solar photovoltaic panels generate electricity whenever it's light. Light energy from the sun hits the photovoltaic cells on the solar panel and is transformed into electricity. Conducting wires carry the electrical current from the panels to the inverter and then into your home. When it's light and you turn on your electrical appliances, they will be powered by electricity you are generating.

Any excess electricity will be exported to the national grid. If you turn on your appliances when your panels aren't producing electricity, you'll use electricity from the grid as usual. 

Before the installation process can
begin, you will have to arrange a survey with a reputable solar panel installation company.

And the number of panels that you put on your roof depends on a number of factors: the size of your roof, the direction in which it faces, the amount of electricity that you wish to generate and how much you wish to spend. 

The installation will be done in stages.
The whole process can take as little as one day, depending on the size of the system.

We caught up with solar panel installation company manager Guy Hewitt to see an installation in process. He explained: 'The process is quite straightforward actually. Before we get to the site we would have already surveyed it, so we'll have produced a detailed plan of what we're going to do on the roof.

'
The next phase is to mark up and set out the array on the roof, then we'll begin lifting tiles, finding the rafters and setting out where we actually are going to insert the roof hooks into the roof. 

'To install the roof hooks,
we lift up the tile, find the rafters, then insert the roof hook into the rafter - the tile is then set back down and weathered if necessary. We continue all the way along the roof to create, if you like, parallel lines of roof hooks. After that the rails are bolted onto the roof hooks, and when they're fully secured and in position the panels can be installed onto the rails.

'
The vast majority of roofs in the UK are able to take solar panels. Of course they need to face the right way - we wouldn't be installing solar panels on a north-facing roof. We're really looking for somewhere from east to west or south of that.

'One of the concerns a lot of people have is that there's a possibility that installing solar panels could actually damage the roof. This is not the case. Provided the right roof bolt is used for the type of tile that's on the building, and the roofers have done a professional job, then the roof will be weatherproofed.'

In the house, the direct current from the solar panels comes in through a cable and goes into an inverter box, which converts the direct current to alternating current, which is safer for your home.

And there are two isolator switches - a direct current isolator switch and an alternating current isolator switch - as safety measures. From here, the power is passed around the house. The generation meter indicates how much power your solar panels have created. 

As long as there is enough light,
the panels will start producing electricity immediately.

So, if you're interested in installing solar PV panels, go to which.co.uk/solar to read our solar panel guide and see our checklist for things to watch our for during your installation.

Is my home suitable for solar PV panels?

ideal house for solar panels

Maximum power output from solar panels will be achieved for a south-facing roof with a tilt angle of 30 degrees and no shade

Solar PV panels are worth considering if you have a mainly south-facing roof with little or no shade, and you aren't thinking of moving home in the near future.

Although a south-facing roof would yield the best power output, a southwest or southeast-facing roof should also be fine - but you'd get less power out of the system.

How much energy you could produce with solar panels - and therefore how much money you could make - will depend on:

  • The tilt angle of your roof and its orientation
  • Where you live: the South West gets more sun than the North. This could impact the amount of electricity your system will generate, although not too significantly.

You can find out more in our guide called is solar pv a good investment?

What is the best roof orientation for solar panels?

The table below shows the percentage of the maximum output you will get from a solar PV system, depending on your roof orientation (south, west, east) and tilt angle (source: the Energy Saving Trust). 

@inlinemarker@ Tilt-and-orientation-table @inlinemarker@

Most roofs in the UK are angled at between 30 degrees and 45 degrees. Solar PV panels are not recommended for roofs that face north.

You should also consider both the age of your roof and how strong it is, as PV panels are heavy. 

Solar PV systems are most efficient if you use the electricity they produce during the day. So if you work all day leaving your home empty, you may not reap the full benefits of your solar panels. Shade could be a big problem for solar panels, so no panels should be installed where there is shade from trees, chimneys, walls or other obstructions.

What size of solar PV system is right for my home?

The right size for your home will mainly depend on the roof space available and how much electricity you use. We recommend that you do not buy too large a system as you cannot meet 100% of your demand with solar PV. 

Make sure the surveyor understands your electricity use so that the system is sized correctly. As a guide, an average 4kWp system would cost about £5,000 to £8,000.

Before you install solar PV, read our tips and advice on what you should do, and the questions you need to ask before, during and after a visit from a solar PV installer - see our downloadable and printable solar PV installation checklist.

Do I need planning permission for solar PV?

Contact your council to see whether you need to apply for planning permission for your solar panels. You won’t need planning permission for most domestic solar panels, as long as they respect certain size criteria. However, exceptions apply for listed buildings, buildings in conservation areas and World Heritage Sites. 

Do solar panels need cleaning?

Solar panels are pretty much maintenance-free and should last for at least 25 years. 

Solar PV panels are self-cleaning when installed on an ideal roof slope, and should not require cleaning or only rarely. But if your roof has a fairly shallow pitch or is flat, it may accumulate bird droppings, leaves or dirt, so the solar panels will need occasional cleaning.

Are there any other maintenance or ongoing costs to consider?

Solar PV systems are relatively simple and have no moving parts, so they don't need much maintenance. However, within 25 years you’ll need to replace the inverter, which costs about £1,000 (some installers say it costs less). 

What’s the best way of finding a reputable installation company?

Request a site visit with a technical survey, not a sales visit, and get at least three quotes. Ask for recommendations and addresses of installations in your local area that you could go and see.

Check the Microgeneration Certification website to ensure that your installer is MCS-certified, otherwise you can't take part in the Feed-in Tariff (FIT) scheme. To find installers recommended by other Which? members, use Which? Local

How can I ensure the installation process goes well?

Make sure you don't end up with panels overhanging the roof. Where panels are fitted just above the existing roof, it's good practice that at least 30-40cm should be left between the last panel and the roof edge to allow for access and to minimise the risk of wind blowing the panels off the roof. 

Use the Which? solar installation checklist to ensure you get a thorough survey. Before your installer draws up the plans, ask how much space they're leaving between the panel and the roof edge.

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