Flat Roof Solar Panel Installation: A 2025 Guide

You’re probably accustomed to seeing solar panels installed on sloped roofs in residential areas. However, there’s still a misguided belief that solar panels aren’t as effective when installed on flat roofs. 

In fact, solar panels on flat roofs, especially those on commercial properties, can be highly effective when installed correctly. In some cases, they can even outperform sloped roof solar panels, with the reduced size restrictions that flat roofs offer.  

In this article, we’ll tell you everything you need to know about solar panels on flat roofs, running you through the entire installation process. We’ll also bust the flat roof solar myths that have been holding you back from making this life-changing investment.

Are Solar Panels Less Effective on Flat Roofs?

There’s a common misconception that solar panels aren’t effective when placed on flat roofs. This is somewhat grounded in truth; solar panels do need to be tilted at an angle between 30-35 degrees for maximum efficiency. This is rarely achievable on flat roofs because of high wind exposure, with 10-15 degrees being a more realistic target.

The benefit to flat roof solar panels is that the space on offer can maximise the number of solar panels that can be used. This will increase the energy output created by your system. Solar panels are more suited to the larger, stronger flat roofs of commercial buildings than they are residential flat roofs. 

If mounted correctly, solar panels can be just as effective on flat roofs as they are on sloped roofs. 

The Benefits of Flat Roof Solar Panels

There are many benefits to having solar panels installed on flat roofs, for both commercial and residential properties. They aren’t just environmental benefits either, with solar panels able to save you considerable amounts on your energy bills each year.

Cost Saving

The amount of money you’ll save with solar panels will depend on the size of your system. Commercial properties with a large roof space can expect to save thousands of pounds on their energy bills each year. For residential properties it will be a bit less, although savings can rise to £650 a year. 

Additional incentives, such as the Smart Export Guarantee (SEG) can help you save even more money. The SEG is a government-backed initiative that allows you to sell excess electricity back to the grid. So, your solar panels will be able to start generating money as well as saving it, making it a smart investment.

Freedom of Positioning

Flat roofs allow installers to angle and position panels perfectly for maximum efficiency. In Essex, solar panels are most effective when they are south-facing. With a sloped roof, you aren’t afforded the luxury of choosing which direction the panels face. 

Easy Installation and Maintenance

Understandably, it’s much simpler to install solar panels on a flat roof than it is on a sloped roof. This will make the installation process quicker, potentially saving you money on labor costs. Maintenance work will also be made easier by a flat roof.

Aesthetics

Due to the angle they are installed at, solar panels on a flat roof will often only be visible from above. So, if you’re unsure about the visual aspect of installing flat roof solar panels, you needn’t be. 

[Choosing a company for solar panel installation? Check out our previous work.]

How Are Solar Panels Installed on a Flat Roof?

Flat roof solar installation is a multi-step process. As with all solar panel installations, the process will begin with a professional assessment of the installation area.

1. Structural Assessment

The first step your installer will take is an in-depth assessment of your flat roof. They will analyse its structural integrity, if it has any damage or leaks, and the space available. This will ensure the suitability of your roof for a safe solar panel installation.

2. System Design

Your installer will then begin the design process. They will decide the layout and spacing of the panels, and the tilt angle they need for maximum efficiency. They’ll also decide the type of mounting system you need, picking one of the below options:

• - Ballasted: Solar panels will often be mounted on plastic containers filled weighted down by various means. The weights used vary, with concrete, gravel bags, and water being common options. This prevents you from penetrating the roof’s surface, preserving its integrity. 

• - Fixed: Fixed mounts provide greater structural stability than ballasted systems. The panels will be directly attached to the roof surface, bolted down for security. One downside: it will penetrate the roof surface, potentially affecting warranties.

3. Fixing the Mounts

After designing your system, it will be time to fix the mounts on the roof surface. If you’ve opted for a ballasted system, the mounting containers will be lined up and weighted down. The containers will have a framework fixed to them, on which the panels will be attached.

For fixed mounting, the installer will bolt the mounting framework to the roof. The frames holding the panels will be angled between 20 and 50 degrees, to absorb maximum sunlight. 

The installer will check that each panel is securely fitted, ensuring that they will be unaffected by wind. They will also double check that the panels are secured at the right angle. 

4. Connecting the System

The solar panels will be wired and routed to a combiner box or to the inverter. From here, the electricity produced will be turned from a DC current to an AC current, the type that powers our homes and commercial buildings. 

The AC output will be connected to the building’s electrical panel, where it can be used to reduce electricity consumption from the grid. 

5. Testing and Finalising

Once your solar panel system is installed and connected, the installer will run a series of tests to ensure it’s working properly and efficiently. 

They will run you through how the system works and guide you towards any service and maintenance packages available.

Flat Roof Solar Panel Requirements

We’ve come to the conclusion that installing solar panels on a flat roof is totally viable. However, there are a few requirements to consider before going ahead with the installation, starting with roof strength.

Roof Strength/Issues

Ballasts holding the solar panel mounts in place will need to be heavy to avoid wind uplift. Your flat roof must be able to contain the weight of the ballasts, otherwise you risk causing severe structural damage to the building. The solar panels themselves will provide extra weight that your roof needs to support. 

A professional solar panel installer will be able to perform a professional assessment of your roof. They will advise you on whether the roof is strong enough, where reinforcements are needed, and the type of mounting system you need. 

They will also spot any drainage issues, which could flood your system if action isn’t taken. 

Planning Permission

Thankfully, most flat roof solar panel installations won’t require you to apply for planning permission. If your panels are discreet, not visible from street level, and don’t rise more than 20cm above the roof, you should be covered under permitted development rights. 

However, it’s always best to consult with a local planning authority before you go ahead with the installation. This is especially important if you live or work out of a listed building. 

Sufficient Space

Your roof will need to have sufficient room to fit the solar panel system you are installing. If not, you will risk preventing maintenance access. You’ll also run the risk of shading, preventing your solar panels from absorbing enough light. 

Flat Roof Solar Panel Myths

Solar Panels Don’t Get Enough Sunlight on Flat Roofs

This may be the case if the solar panels were laid flat, leaving them vulnerable to shading and dirt build up. However, current installation methods would ensure that the panels are installed on a tilt, helping to ensure enough light absorption.

Flat Roof Solar Panels Need Constant Maintenance

While flat roof solar panels will need maintenance, they won’t require it more frequently than their sloped roof counterparts. As they’ll be installed on a tilt, they will receive natural cleaning from rainwater. As with any solar panels, you should have them frequently cleaned by a professional.

Solar Panels Will Damage the Roof

With installation from top, MCS certified industry professionals, your flat roof won’t be damaged by solar panel installation. For a start, the installer will carry out an assessment of your roof to ensure it can withstand the weight required.