Is My Roof Suitable For Solar Panels?

February 14, 2024

Installing solar panels on your roof is an important step towards sustainability. Better still, your panels will generate their own power, reducing the amount you need to draw from the grid, lowering your bills. In some cases, panels will even make money, as you can sell your excess power to the grid.

Most roofed homes are able to have solar panels and join more than a million other UK households that have already done it. These trailblazers have put to bed the idea that the UK is too cloudy and northerly to benefit from rooftop photovoltaic (PV) panels, and are already reaping the benefits.

So what are the things you need to take into consideration when working out whether you can have PV panels on your roof? Broadly, they fall into three categories:

Efficiency and structural factors determine whether your panels will be cost effective. First, there’s the amount of energy you can expect to generate. Second, you need to consider any work you’ll need to do to modify your roof. As for planning permission, that can stop any solar ambitions in their tracks, but bear in mind that it’s quite uncommon to be refused permission, and even then there are routes to appeal or change your plans.

So, if you’re asking yourself “Can I have solar panels on my roof?” these are the factors to consider.

Legal factors

Before you trouble yourself with working out if your solar panels would be efficient and structurally sound, it’s a good idea to make sure you’re actually allowed to install them. We’d say that for 99% of those seeking roof panels, planning permission won’t be a problem. Successive governments have promoted green energy, and hurdles to installation are minimal.

But what about that 1%? Generally, to be denied the right to install solar panels, you’d have to fall into one of these categories:

The property is a listed building
The house is within a conservation area
There are reasonable objections from a neighbour
The panels would cause a hazard, for example dazzling motorists

While the first two are pretty much non-negotiable at the moment, you might be able to work around the other two.

First, (un)neighbourly opposition needs to be truly justified. It can’t simply be that the neighbour doesn’t like the look of solar panels. It’s your property, and these installations usually come under “permitted development”, which means you don’t even need to seek permission.

However, some objections are justified. Examples would include where angled panels (for example on a flat roof) cast significant shadows on their garden or living area. Similarly, causing excessive glare and reflection could be grounds for refusal. Generally, however, as panels sit flush with roofs and point skyward, these issues do not apply.

If you live near a busy road, there’s a small chance that your panels could reflect sunlight directly into motorists’ eyes at certain times of the day and year. If you think there’s a risk, it’s best to seek permission rather than being forced to take them down after accidents or complaints. Investigators can calculate precisely whether the risk would be significant with regard to the motion of the sun. If your plans are considered risky, it could be a case of adjusting the angle or situating the panels elsewhere.

Efficiency Factors

Solar panels are at their most effective when they are pointing directly at the sun. Anything less than 90 degrees is less than optimal. This presents a few challenges:

First, in the UK, the sun rises in the east, passes over the south, and sets in the west. So whichever way you point your panels, there will always be times when they are not at 90 degrees (if ever).
Second, the UK is quite far north of the equator, so the midday sun never gets above about 60 degrees overhead in the summer, and as low as 15 degrees in the winter.

However, remember that this is about efficiency, rather than ability. A panel that’s working at 50% of its maximum possible efficiency is still generating power, which will still probably be enough for your needs.

Although direct sunlight is optimal, you can still generate plenty of electricity under cloudy skies. In fact, clouds can act as a diffuser, which means more light will hit the panels after the sun has passed overhead, rather than them being in shadow on a sunny day.

So, ask yourself these questions:

Which direction does my roof face?

Most houses have a standard gable (triangular) roof or a hip roof (where there’s no gable but the roof slopes towards the ridge). So unless you have a gable roof or live in a terraced house where the roofs face directly east and west, you’ve probably got at least one roof that’s facing towards the sun for a good part of the day.

Are east or west-facing roofs suitable?

East- or west-facing roofs will still harness light throughout the day, but a south-facing roof is always going to be better. An east-facing roof will gather more in the morning, while a west-facing roof will gather more in the afternoon. However, unless your ridge points precisely north-south, there will always be one side that’s a little bit better than the other.

What angle is the roof at?

Roof angle (pitch) ranges from very steep to flat. On houses with pitched roofs, the angle is normally in the 30–50° range. The angle combines with the direction to determine how well it will gather light if the panels are set flush to the roof. As it happens, these average roof angles are good for gathering light.

What about flat roofs? Well, clearly, solar panels mounted on a flat roof would be pointing directly up at the sky, so would never be firing on all cylinders in the UK. However, you can mount them at a tilted angle. Better still, that allows you to choose whatever angle is optimal, unlike with a pitched roof. Flat roofs are invisible to people at ground level, so there’s no aesthetic cost.

Is your roof big enough?

You could have a single panel on the only available section of roof, but in reality it might not be worth the effort. Much of the cost of solar panel installation is in connecting your setup to the grid and batteries, as well as potentially one-off items like scaffolding and installers’ labour.

Each extra panel does add to the cost, but the more panels you have, the better value your one-off expenses become. If you have money to burn and are committed to green energy, go for it! Otherwise, a small number of panels will take a lot longer to pay for themselves in energy savings.

Structural Factors

British houses’ roofs are built to last. They’re designed to shrug off all our weather can throw at them, from baking summer sun to gale-force winds, incessant rain and potentially several tonnes of snow. Now we’ve got the British Tourist Board stuff out of the way, we need to ask ourselves about the roof requirements for solar panels.

The good news is that the built-in strength makes the vast majority of roofs perfectly capable of handling a set of solar panels. Each panel weighs about 18 kg, so even with a thick coating of snow, it shouldn’t trouble your roof.

Exceptions arise when roofs are old and in need of repair. A structurally weak roof will certainly need strengthening ahead of panels being installed. If you’re in doubt, check with a structural engineer, but a reputable solar panel installer should be able to determine whether your roof will handle the extra weight.

Certain roofing materials, particularly thatch, are not suitable for solar panels. But in general, panels can be installed on most kinds of roof.

Another structural factor could be the presence of a parapet on a flat roof, or other parts of the building casting a shadow on the relevant area. This might not rule out installation completely, but could seriously affect the efficiency of the panels.

You don’t need to calculate anything

If all those mentions of east-west orientation and roof pitch are bamboozling your brain, don’t worry. Using our calculator, we can work out exactly how much energy your roof-mounted panels could generate.

It all starts with finding your property on the map (just enter your postcode). But we’re much more precise than that. Once you’ve located your property, you draw your roof, and tell us roughly what angle your roof is (i.e. steep, gentle or flat). Given those geographic and orientation factors, we can work out how efficient your roof’s panels would be.

We’ll also ask a few questions about your current energy usage and what your house is like. Then, our calculators will get to work and give you an estimate for how much energy you can generate and how much you’ll save, for a range of cost options.

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