Solar Panels on Flat Roofs: Costs, Pros & Cons

With millions of UK homes switching to solar power, it has become the fastest-growing renewable energy solution. Installing solar panels can lower your annual energy bills, boost your property’s value by £1,891 – £2,722, and significantly reduce your carbon footprint.

But what if your home has a flat roof?

Many people assume that solar panels only work on pitched or sloping roofs, overlooking the potential to generate clean, renewable energy from a flat roof. However, not only is it possible, but it also comes with unique advantages.

This guide covers everything you need to know about installing solar panels on flat roofs, including the benefits, potential drawbacks, and key considerations before making the switch.

Pro tip: Avoid upsells and confusing packages—choose a provider with a clear, fixed-price quote that won’t change. Heatable, a Which?-approved solar installer, offers transparent pricing with no surprises.

Key Takeaways:

You can install solar panels on flat roofs and reap the benefits of solar energy.
Flat roofs allow easier installations, are aesthetically discreet, and have improved safety, space efficiency, and design versatility.
Flat roofs may require more structural consideration, proper drainage, cleaning, and waterproofing to secure the panels and your property.
The optimal angle to mount your panels on a flat roof is 39 degrees.
You must fix the panels on the flat roof or weigh them down to prevent wind uplifts.

Is it Possible to Install Solar Panels on Flat Roofs?

Yes. It’s feasible and practical to install solar panels on flat roofs. Most solar panels are suitable for flat roof mounting and provide adequate space for many panels.

Installing solar panels on flat roofs involves mounting the panels at an angle to achieve the optimal tilt and allow maximum sun exposure.

Keeping the solar panels horizontal on flat roofs can restrict the power they generate and prevent rainwater from running off them.

Adequate support and precise positioning are necessary to ensure durability and efficiency, and with proper planning, you can harness solar energy on a flat roof and generate sustainable power.

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Benefits of Installing Solar Panels on Flat Roofs

Easier Installation and Maintenance

Flat roofs are more accessible than sloping roofs, so installation and maintenance are smooth and straightforward.

Installers don’t have to worry about angled surfaces, making placing and maintaining panel systems more effortless and cheaper. Fewer adjustments translate to less time and effort, which can help you save on costs.

Aesthetically Discreet

Flat roofs allow solar panels to be less visible from the street. Passersby won’t be able to notice them, and they won’t alter the visible impression of the property or building where they’re mounted.

Improved Safety

With flat roofs, you don’t have to worry about solar panels being positioned at steep angles or slopes that can make them susceptible to damage from heavy rain, strong winds, and snow.

There’s less risk from extreme weather events, keeping your investments safe and potentially extending their lifespan.

Space Efficiency

Flat roofs allow maximum space utilization, and you can install a more extensive solar panel array than sloped roofs.

They’re suitable for large residential properties or commercial buildings with high energy demand since they allow you to maximize the energy production potential.

Design Versatility

Flat roofs give you a versatile canvas on which to design your solar panel arrangement.

They offer flexibility in panel arrangements and placements, allowing creative layouts that can optimize sunlight exposure.

Easy Removals and Upgrades

Thanks to easier access and a hassle-free path to solar panels, flat roofs make it cheaper to swap out failed panels or replace the entire system.

Studies show that flat roofs offer easy access for technicians, and they don’t have to worry about navigating steep angles, allowing a stress-free, less costly experience.

Drawbacks of Installing Solar Panels on Flat Roofs

Structural Considerations

The mounting system required to install solar panels on flat roofs and the panels’ weight can be a concern.

Weighted slabs or ballasts are used to weigh down mounting systems, and your roof may have a weight limit, especially if it’s an old building.

You must ensure the roof can handle the extra weight to avoid compromising its structural integrity.

Water Damage

Flat roofs can quickly accumulate standing water, damaging your solar panel system. You’ll need proper drainage to prevent water from pooling around the solar panels.

You’ll also need a tilted mounting system to allow the rain to fall away from the surface of the solar panels instead of collecting on the flat surface.

More Cleaning

Flat roofs have more areas where dust, debris, and other environmental contaminants can collect or get trapped, making it necessary to clean the area around the solar panels more frequently.

Leakage Risks

Installing solar panels on flat roofs may require penetration where the roof is drilled to fix the mounting system or solar panels firmly.

If improperly sealed, this can cause leaks, so you must prioritize waterproofing to prevent water infiltration.

Considerations for Installing Solar Panels on Flat Roofs

Angles and Orientation

It’s essential to consider the angles at which your solar panels are mounted on a flat roof.

The panels must be correctly angled to maximise sun exposure, and you may need to use tilt legs, ballasted mounting systems, or triangle mounts.

Studies show that the optimal angle for solar installations is between 30 and 45 degrees, with the best angle in the UK being 39 degrees.

You should also consider the best orientation for solar panels. In the UK, it’s due south, meaning a solar panel angled at 39 degrees facing due south can capture up to 95% of sunlight throughout the year.

Avoid placing your solar panels horizontally on a flat roof, as this will limit sunlight absorption and reduce energy production.

Debris, dust, dirt, and water can also quickly settle on the panels’ surface when placed horizontally, reducing the solar system’s efficiency and increasing the risk of damage.

Some warranties can also become null and void when you place your solar panels horizontally because of potential damage.

Related solar guides:

The Impact of Wind

Solar panels installed on flat roofs are vulnerable to wind uplift since they don’t sit flush on the surface.

You should avoid installing the panels too close to the edge and ensure they’re fixed to the roof or weighed down to improve safety and longevity.

The mounting system should be strong enough to keep the solar panels secured to the roof and withstand strong winds and storms.

Final Thoughts on the Feasibility of Installing Solar Panels on Flat Roofs

Installing solar panels on flat roofs is feasible, and they can be as beneficial as installations on pitched roofs.

With proper planning, design, and installation, a flat roof can be an excellent platform to help you harness solar energy and save money on energy bills.

Sources used in this article:

https://solarenergyuk.org/wp-content/uploads/2021/10/The-Value-of-Solar-Property-report_SEUK.pdf
https://www.mdpi.com/2673-9941/3/4/35
https://eprints.whiterose.ac.uk/177719/1/Manuscript.pdf