Can You Put Solar Panels on a Flat Roof?

Rows of solar panels on flat roof

By 8 min read


As time goes on, the popularity of solar panels in the UK will only continue to grow. In fact, as of September 2019, the UK’s total solar capacity stood at 13,284.3 megawatts (MW), spread across 1,015,961 installations

Houses come in all shapes and sizes – especially in Britain, with our mix of new-build houses, old cottages, traditional farmhouses, and terraced homes – but are solar panels suitable for homes that have flat roofs?

We’ll answer this question further down the page, along with some other roof-related questions that may be lingering in the back of your mind.

If you’re already set on getting a solar panel system for your home, we can speed up the process for you. Rather than scouring the internet for the best companies and prices, simply answer a few short questions on this form. We’ll pass your details on to our trusted suppliers, who will then get in touch with free quotes for you to compare.

Rows of solar panels on flat roof

Can you have solar panels on a flat roof?

Yes! Although flat roof solar panel systems are more commonly found on commercial buildings, they also work well on domestic properties.

How do they work?

The solar panels that are used on a flat roof are exactly the same as the ones used on a tilted roof. You can technically lay the panels down on a flat roof – just as you would on a slanted roof – but this will restrict them from absorbing as much sun as possible, and might also lead to water damage.

That’s why a tilted-mounting system usually needs to be installed as well as the panels – this will help them self-clean in the rain, and avoid damage from pooling water.

Can you also have solar thermal systems on a flat roof?

Yes, you can keep your home warm during the chillier months by installing solar thermal systems on a flat roof. Similar to regular photovoltaic (PV) systems, solar thermal panels can be attached to a flat roof with a mounting rack.

Advantages and disadvantages of flat roof solar panels

Getting solar panels for any property comes with its pros and cons, but with a flat roof, you have a few extra things to think about.

Advantages of flat roof solar panels

  • Flat roofs provide easy access for installation and maintenance
  • Panels probably won’t be visible from the street
  • You’ll be able to save money on electricity bills
  • You’ll be able to shrink your carbon footprint
  • They're low maintenance
  • Labour costs can be more affordable

Disadvantages of flat roof solar panels

While there are a number of disadvantages to flat roof solar panels, bear in mind that most of these can be resolved by using a tilted mounting system.

  • Panels get far dirtier over time – On a tilted roof, rainwater usually washes dirt and debris off the panels. Without this self-cleaning feature, the dirt will stay there, reducing the solar panel’s efficiency
  • Without additional mounting equipment, panels won’t get as much exposure – Solar panels usually face southward on a tilted roof, in order to increase sun exposure and create more energy. Laid flat, panels are unable to convert as much energy because they will not be getting as much sunlight
  • Flat roof panels can make some warranties ineffective – When panels are laid flat, water sits between the frame and the glass coating of the module. Given this gap is only sealed with silicon, which easily degrades over time, panels are likely to become damaged faster than usual

On top of this, installation can come with a few added costs. To avoid the disadvantages above, many people invest in mounting systems. Generally, solar panel racking should make up roughly 3% of the total system cost, although this will fluctuate depending on the brand and type of rack you get, along with the amount you need to buy.

What’s the optimum angle for flat roof solar panels?

To avoid water damage, it’s wise to invest in a mounting system that props your panels up. Roofs come in all shapes and sizes but, generally, panels will need to be mounted at a 20-50 degree angle to absorb as much sunlight as possible.

And, as an added bonus, panels at this angle have a better chance of staying clean, as rainfall will remove debris and dirt that could reduce the panel’s efficiency.

Installers will often use specialist equipment to mount panels at the perfect angle, so make sure you contact a qualified professional to carry out your installation.

Want to find trusted installers now? Get a head start by filling out this short form – after answering a few questions about your property, our professional suppliers will be in touch with free quotes for you to compare.

Installers fitting solar panels on flat roof

Do you need planning permission for flat roof solar panels?

Similar to installing solar panels on a slanted roof, in most cases, you won’t need planning permission to install solar panels (along with a mounting system) on a flat roof. The only exception is if you live in either a listed building or a conservation area.

Of course, when it comes to building improvements, not everything is so straightforward. If you have any doubts or concerns about whether you need planning permission, it’s a good idea to check with The Planning Portal – the national planning application service for England and Wales.

Things to consider before installing flat roof solar panels

Do you have the right weather conditions?

Weather is an important thing to consider when it comes to solar panels – especially if they’re sitting on a flat roof.

We’ve already mentioned how rain can damage panels on a flat roof, with water pooling causing the silicon to degrade, but thankfully this can be easily resolved with a mounting rack. High winds, however, can be a bit more tricky to deal with.

If you live in a particularly windy area, it’s a good idea to take a few extra precautions to keep your panels pinned down. The most popular way of doing this is either by fixing the panels to the house, or adding weight to them. 

  • Fixing panels to your home – This involves drilling into the roof itself and securing the brackets to keep the mounting frame stable
  • Adding weight – If you’re unable to penetrate your roof, a good alternative is to simply add weight to the structure. The mounting frame can slot into concrete ballasts (heavy slabs) and make the panels much more wind-resistant

How much does it cost to install solar panels on a flat roof?

Generally, installing solar panels on a flat roof will cost around £750 – £900 per kW – far lower than the £1,250 per kW it costs to install panels on a slanted roof.

Of course, prices vary depending on a range of things, including the number of panels you get and which mounting technique you use.

The key reason flat roof solar panel installations are cheaper is largely down to the price of labour, which typically makes up about 10% of total solar panel system costs. This partially comes down to the logistics of climbing around on a steep roof, which usually requires safety equipment to make sure it’s safe.

Thankfully, installers can walk around freely (and safely) on a flat roof, making the process much easier and often cheaper.

On the other hand, there are a few factors that can make solar panels more expensive on a flat roof, including the added equipment (such as a tilted mounting rack) needed to maximize the panels’ electricity production. Paying for these added materials alone mounts up, but you’ll also have to consider the labour costs involved – extra gear might mean the installer needs to spend longer installing the panels.

How much money could you save with solar?

According to the Energy Saving Trust, a typical 4 kWp solar PV system can save you between £85 and £220 every year – although this will vary depending on a range of factors.

In 2019, we carried out a study by cross-referencing the cumulative cost of a 3.5kW solar PV system with cumulative energy bill savings. We found that if you were to install solar panels today, you would break even by 2039. 

Next steps

Domestic renewable energy is becoming increasingly common across the UK, and as one of the most space-efficient ways to harness green energy, solar is leading the way. Plus, as we’ve discovered in this article, having a flat roof doesn’t have to be a barrier to installing solar panels at home.

So, if you’d like to join the UK’s growing list of solar-powered homes, it’s time to start hunting for the perfect set of panels.

Luckily, we can help with that – all you have to do is pop your details in this quick form. Once we’ve got your information, we’ll pass it on to our trusted suppliers, who will then be in touch with free quotes for you to compare.

You’ll be on your way to smaller bills and an even smaller carbon footprint in no time!

Beth Howell Writer

Beth has a real passion for green living. She’s been absorbed in eco research for over three years, and has become quite the expert. Whether you’re after a new set of solar panels, a home energy improvement, or you want to catch the latest eco news, she’s got your back.