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Installing solar panels on a flat roof can save you hundreds of pounds a year on your energy bills. Find out more in this guide.
Solar panels are more versatile than you think. You don’t necessarily need a sloped roof to benefit from solar energy – you can still install some of the best solar panels on a flat roof and generate enough electricity to power your home.
In our comprehensive guide, we cover whether you need planning permission to install solar panels on a flat roof, the added mounting costs, and how much you can save on your energy bills.
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The average home can save more than £1,100 every year with solar panels!
Not only can you put solar panels on a flat roof, they’re actually easier to install than on a sloped roof. This is because solar panel installers have much more room to stand and manoeuvre the panels on a flat roof.
Flat roof solar panels can be a great way to use otherwise wasted space, while saving hundreds of pounds a year on your energy bills.
As of the end of 2023, you no longer need to seek planning permission to install solar panels on a flat roof. Most of the time, the installation will fall under ‘permitted development’, unless:
If any of the above apply, you will need to seek planning permission.
As with normal solar panels, flat roof solar panels convert sunlight into electricity. You can then use this energy to power your home and its appliances, store the excess in a solar battery to use at a later date or sell it back to the grid through the Smart Export Guarantee (SEG).
The main difference between solar panels on a flat roof and on a sloped roof is how they are mounted. Although it is possible to lay your solar panels flat, most of the time they would need to be tilted to optimise for efficiency based on which direction your roof is facing, as well as to minimise shading.
Typically, the most efficient angle for a solar panel is 30 to 40 degrees to the horizontal, facing due south. This position guarantees maximum sun exposure and energy generation.
However, solar panels on flat roofs may be better off with less of a tilt. Firstly, the greater the tilt angle, the more at risk the panels are from wind, increasing the amount of ballast you need. Secondly, the more your panels are tilted, the more likely they are to be shaded for part of the day. To avoid this, they will require a bigger gap between each row of panels, limiting the amount you can install on your roof.
Your solar panel installer will recommend the best tilt angle for your panels and the most suitable mounting technique, informed by which direction your roof faces.
There are a few different mounting options available for flat roof solar panels, depending on the condition of your roof, the direction it faces and how much you want to spend:
With an east/west mounting system, panels will be placed back-to-back, tilted towards the east on one side and west on the other.
There’s a small gap between rows of panels to minimise shading and maximise the amount of panels you can fit onto your roof. The back-to-back nature of the system also increases wind resistance, meaning less ballast (heavy material such as concrete or gravel) is required to keep the panels in place.
While an east/west system is less efficient than a south-facing system, as panels facing due south generate the most energy, that is compensated for by the increased number of panels you can fit on your roof.
With a south-facing roof mount, your panels will be placed on triangular metal frames, with a significant gap between rows of panels in order to prevent shading. Ballast will then be placed underneath the panels, again to prevent unnecessary shading.
South-facing roof mounts can require up to 10 times more ballast than east/west mounts, placing increased pressure on your roof. And while they have greater efficiency than east/west systems, you’ll be able to fit fewer panels on your roof due to the gap required between each row.
If you have a flat trapezoidal roof (i.e. a roof with a very slight pitch), your solar panels will normally be placed on metal triangular frames which are then screwed directly into the roof itself.
With console bins, your solar panels will be fixed to plastic bins that are moulded to a preset angle. These bins are filled with ballast to weigh them down and protect your panels from heavy winds.
We estimate installing flat roof solar panels for the average 3-bedroom household in the UK would cost around £10,500, including a battery.
| Property size | System size | Number of panels | Estimated cost of solar panels and installation (including solar battery) | Estimated cost of flat roof solar panels mounting system | Total cost of installing solar panels on a flat roof |
|---|---|---|---|---|---|
| 1 bedroom | 1.5kW | 4 | £6,200 | £300 | £6,500 |
| 2 bedrooms | 3.0kW | 8 | £8,200 | £600 | £8,800 |
| 3 bedrooms | 4.5kW | 12 | £9,600 | £900 | £10,500 |
| 4+ bedrooms | 6.0kW | 16 | £12,000 | £1,200 | £13,200 |
Typically, the cost of solar panels on a flat roof is more expensive than on a sloped one due to the added cost of the mounting system. However, there is a chance that the labour costs for installation on a flat roof may be lower (depending on your chosen installer), meaning the overall cost will be similar. This is because it’s typically easier and less time-consuming to install flat roof solar panels than those on a sloped roof.
How much you can save with flat roof solar panels and how long it will take you to break even depends on:
On average, a 3-bedroom household will take around 12.7 years to break-even on flat roof solar panels.
Flat roof solar panel savings based on property size
| Property size | System size | Estimated cost of solar panels (including installation, battery and mounting system) | Average savings (including battery and SEG tariff) | Average break-even point |
|---|---|---|---|---|
| 1 bedroom | 1.5kW | £6,500 | £305 | 21.3 years |
| 2 bedrooms | 3.0kW | £8,800 | £609.27 | 14.4 years |
| 3 bedrooms | 4.5kW | £10,500 | £829.91 | 12.7 years |
| 4+ bedrooms | 6.0kW | £13,200 | £1,042.55 | 12.7 years |
As with pitched solar panels, flat roof solar panels can save you hundreds of pounds on your energy bills, protect you from rising energy prices, and reduce your carbon footprint.
However, there are additional pros and cons of solar panels on a flat roof when compared to installing them on a sloped roof.
You can opt for national solar panel installers that work across the UK, or smaller firms local to your area. When comparing installers, pay attention to:
You can get free quotes from up to five solar panel installers by filling out our form below and answering a few simple questions about your home.
If you intend to stay in your current home for the next ten years at least – as it takes at least 10 years for your solar panels to pay back – it is worth considering flat roof solar panels as you can save hundreds of pounds on your energy bills, while taking advantage of a space previously unused.
It is possible to mount solar thermal panels onto a flat roof. These panels generate heated water instead of electricity, and are generally used for heating and boilers.
You’ll typically need to leave 0.5-1m between your solar panels and the edge of your flat roof.
