Flat Roof Solar Panels

Published: November 2023.


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Are flat roofs suitable for solar panels? When would you consider a flat roof solar panel system?

Flat roof solar panels are used to maximise solar generation from a dormer, flat roof extension or garage roof. Flat roof solar panels can be mounted in a free standing tub or metal framework (pictured aboved).

Flat roofs can be perfect for solar panels - the solar array is usually hidden from veiw at street level, there is often minimal shading and the optimum pitch can be used, invisibly powering your home from space that would otherwise be wasted.

Often a flat roof solar panel installation can be better than a pitched roof.


What is the best pitch for a flat roof solar panel system?

This applies to all solar panel systems, not just flat roof solar systems.

The optimum pitch when facing due South is 30 degrees (for the UK).

Now we need to answer the question - what's the optimum pitch for a North facing array? The answer is 0 degrees. A flat pitch is equally facing South, West, East and North facing.

Therefore we can say that - the optimum pitch is 30 degrees when facing due South in the UK and the optimum angle for solar panels reduces from 30 degrees to 0 degrees the closer it gets to North.

A good rule of thumb is that 30 degrees is best for a South facing flat roof solar panel system and 0 degrees for anything more Northernly than East or West.

30 - 10 degrees is the best pitch for a flat roof solar system. A 0 pitch would mean the panels do not clean themselves in the rain, negating any benefit.


Advantages of a Flat Roof Solar Panel System

  • Often hidden from view, making use of space that would otherwise be forgotten.
  • Many do not require additional planning permission.
  • You are not limited to a certain model of solar panel.
  • Make use of more space. Flat roofs are usually easily accessible.
  • Pitch flexibility. With a pitched roof you do not have a choice. A flat roof solar system can vary from 30-10 degrees depending on the mounting chosen.


Disadvantages of a Flat Roof Solar Panel System

  • Limited to landscape layout
  • Can require planning permission if extending 200mm above the ridge/edge of the roof.
  • Where a lot of ballast is required a structural survey is needed to assess the ability of the roof to support the additional wieght.
  • More space required per panel. So panels do not shade each other. A flat roof system has to be spaced correctly.


4 kW solar system cost image
Flat roof solar panels in a Renusol Console+ tub

A Flat Roof Solar Panel System using Renusol Console+ tubs. 

Application: When single file installation is required and less space available. Pitch: 30 degrees.
Negative: High ballast requirement 

Flat roof solar panel system using VanDerValk mounting

4 panel flat roof system using VanDerValk flat roof mounting*

Perfect for dormer extensions. Low ballast requirement. Pitch: 10 degrees.

Negative: Landscape only.

Take control of your energy supply

Negative electricity bills

Generating more energy than you use could turn your electricity bills negative - like the customers below.

The marginal cost of adding panels to a 4 kW solar system is negligible, you may as well use the space available and go larger.

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Flat Roof Solar Panel System FAQs


The free standing tubs (Renusole Console+) or the metal framwork (Van Der Valk flat roof mounting) are weighted down using ballast blocks according to the manufacturers calculations based on the height of the building, solar panel size and wind zone,. These ballast calculations are tested in a wind tunnel by the manufacturers.

Just being weighted down can sound a bit scary but it's almost impossible for one person to move them once the ballast is in place. 

We only use ballasted systems to avoid penetrating a flat roof.

As discussed above. The best pitch is 30 degrees when facing due South. 10 degrees when facing East or West.

Solar panels on a flat roof should lie flat as this would stop them being self-cleaning when it rains.


If the manufacturers specifications have been followed and the correct ballast has been used then high winds shouldn't affect the panels.

An example of this is the fact that a solar panel coming off a roof would be huge news for the climate & technology sketical media yet there hasn't been any stories to that affect despite 100,000's of ballasted flat roof solar panel systems being installed worldwide.

Most roof warranties are compatible with ballasted flat roof mounting. Fixing into the substructure and pentrating the roof may affect the warranty as the original manufacturer can not longer be certain of watertightness. It's worth checking with your roofing product manufacturer.

For this reason, we only use ballasted systems unless requested otherwise.

If the system extends beyond the ridge or edge of the roof by 200mm then yes, you will require planning permission. We can model this for you let you know if the panels would extend above the ridge.

A lot of flat roofs will not require planning permission - most garages, dormer extensions and flat roof extensions will not require permission.

Here in Brighton & Hove - a recent flat roof on a dormer extension (picture above) required planning permission as it extended above the ridge of the roof. Planning permission took 2-3 months.