Roof and property suitability

The short version

Your roof matters more than almost anything else in a solar plan, because it sets how many panels fit, how much power they make, and how much the job costs. Three things matter most: which way the roof faces, how much shade it gets, and how sound it is.

An online check can spot the obvious problems, yet it cannot replace a survey. This page shows what to look at first, so you can judge a quote with confidence.

For the wider picture of how a system works, see how domestic solar panels work. For the next steps once you have a sound roof, see our guide to planning your installation.

Which way your roof faces

A south-facing roof gives the most power over a year. Energy Saving Trust calls an unshaded south roof ideal. East and west roofs still work. They tend to make around 15 to 20 per cent less than a south roof, according to the same source.

The gap does not tell the whole story, because timing matters too. East panels make more in the morning. West panels make more in the afternoon and evening. If you use most of your power at those times, you may use more of your own solar power.

Energy Saving Trust does not recommend panels on a north-facing roof, because they would not get enough sun to be worth it. Our post on east-west and flat roof solar explains how those layouts perform.

Installers also use your roof tilt, since MCS says its standard estimate depends on postcode, tilt, direction and shade. So a good quote should state the tilt and direction it used.

Shade matters as much as direction

Shade comes from trees, chimneys and nearby buildings. However, Energy Saving Trust says it can have an even bigger effect than direction. A shaded south roof can make less than a sunny east or west roof.

Installers should assess how shade falls through the day and across the seasons. The aim is to place panels where they get the most steady light, while keeping them clear of shaded spots.

If shade is hard to avoid, ask about optimisers or microinverters. These let each panel work on its own, so one shaded panel does not drag down the rest. If a tree can be trimmed, your installer may suggest that too. Energy Saving Trust notes that optimisers add nothing if your roof has no shade.

How many panels will fit

The usual size is about 4.5 kilowatts peak (kWp). For example, Energy Saving Trust says that size needs roof area of around 20 to 30 square metres, and about 12 panels.

For a rough guide to how many panels typically fit, Energy Saving Trust gives these figures. A mid-terrace house takes about four panels. An end-terrace or semi-detached house takes about eight. A small detached house takes about 12, and a large detached house takes about 16.

These are only starting points, because the final number depends on the roof shape, chimneys, skylights and shade. It can also depend on local planning limits and on the grid. Your installer assesses export limits as part of the design.

More panels are not always better. Our post on how many solar panels you need explains how to match size to your use. The post on how much solar panels cost shows how size and roof type change a quote.

Roof condition and structure

The roof must carry the panels for the life of the system, since Energy Saving Trust says panels should last 25 years or more. Energy Saving Trust adds that an installer may suggest renewing the roof covering first, so the roof stays in good condition under the panels.

MCS sets clear rules for installers. For example, they must make sure a suitably competent person checks that the roof structure can take the load. If the roof is unusual, or there is any doubt, they must consult a structural engineer. MCS lists warning signs such as structural distress and past changes that removed or cut timbers.

MCS also expects evidence that the roof stays watertight after the work. It also expects the customer to be told to update the building’s fire risk assessment. In Wales, the Welsh Government says building regulations normally apply to roof panels, and the roof’s ability to carry the load must be checked and proven. Some strengthening work may be needed.

Ask your installer how they will check the structure, the fixings and the waterproofing. Ask what happens if they find a problem. Our guide to solar panel maintenance and lifespan explains how roof care fits with the life of the system.

Flat roofs, outbuildings and gardens

Yes, you can fit panels on a flat roof. They are normally tilted up to boost output. Many flat-roof systems are weighted down so that nothing pierces the covering, so the roof must be strong enough for the weight.

Energy Saving Trust notes that a flat roof job can be more complex and cost more than a pitched roof. If the roof cannot carry the weight, the installer must use fixings that keep rain out. Sometimes it is cheaper in the long run to renew the roof covering at the same time.

You can also use a garden frame or the roof of a shed or garage. Garden panels are easy to clean, but they face more risk from rodents and knocks. An outbuilding without its own power supply adds the cost of a cable run. MCS defines a pitched roof as one between 10 and 70 degrees.

Planning rules for your property

Most homes do not need a planning application, because panels are usually permitted development. But the details differ across the UK, and 2026 brought changes in England.

In England, the Planning Portal sets the limits. On a pitched roof, panels must not rise above the highest part of the roof, except the chimney. They must stick out no more than 200 mm. On a flat roof, the top of the equipment can be no more than 600 mm above the highest part of the roof.

You cannot use permitted development if the building is in the grounds of a listed building or a scheduled monument. In a conservation area or World Heritage Site, panels must not go on a wall that fronts a highway. Flat roofs on designated land, such as national parks and conservation areas, need prior approval from the council.

Planning Portal says the rules were updated on 27 August 2026, with a 12-month transition until 27 August 2027. The new rules add limits for plug-in solar and for how far panels can stick out from walls and balconies. Check the current page before you start.

Wales has its own rules, although they are similar. The Welsh Government says most homes can have roof or wall panels as permitted development, with a 200 mm limit and no panels above the ridge line. Listed buildings need consent. Conservation areas need it if panels can be seen from the highway.

In Scotland, the Scottish Government’s guidance says permitted development classes cover solar on walls and roofs and free-standing solar. Those classes carry limits, so check them before you start. Northern Ireland has separate planning and building rules, so ask your local council.

Our post on whether solar panels need planning permission goes deeper. Meanwhile, if you rent, or own a leasehold flat, the Planning Portal also warns that you may need permission from your landlord, freeholder or management company.

What to do next

Start with a simple walk-round, since it costs nothing. Note which way each roof slope faces. Look for trees, chimneys and tall buildings that could throw shade. Take photos of the roof from the ground, and note the age of the covering.

Then gather quotes from certified installers, because the answers will differ. Ask how each one checked direction, tilt, shade and structure. Our guide to choosing a solar installer lists the questions to ask. A good installer will explain the survey in plain words and put the findings in writing.