A Guide to Solar Panels on Flat Roof

Have you ever looked up at your flat roof and wondered if it was a suitable location for solar panels? Perhaps you are concerned that the lack of a steep angle could limit the panels’ exposure to sunlight, or unsure if the panels will interfere with drainage of water from your roof?

Worry not, because this guide explores everything you need to know about solar panels on a flat roof, including how they can be installed and optimised for sunlight exposure and whether or not they’re a good choice for your home.

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Can solar panels be installed on a flat roof?

In solar terms, ‘flat’ tends to describe a roof that is angled at less than 10 degrees, and panels that are tiled at less than 10 degrees when taking into account the angle of the roof. The straightforward answer to whether solar panels can be installed on flat roofs is a resounding yes. In fact, commercial premises are more likely to have a flat roof than a residential property, yet many businesses use solar power, which indicates that putting panels on a flat roof can be done successfully.
However, doing so involves overcoming a few hurdles. A flat roof lacks the tilt that allows panels to absorb as much sunlight as possible. Instead, installers must achieve the proper angle for solar panels by tilting the panels themselves. This can be done by mounting the panels onto a racking system known as a ‘tilt rack’. The racks can be adjusted to achieve the angle needed to maximise the panels’ exposure to sunlight.

It’s also possible to lay panels flat on a flat roof but doing so can risk water, dust or debris pooling or sitting on the panels rather than draining away as it would on an angled panel, potentially causing the panels to deteriorate more quickly than they otherwise might.

Aside from committing to regular cleaning if you opt to lay your panels flat, SolarQuotes notes that you can buy frameless solar panels that allow water to drain off the panels more easily or buy panels with drainage channels at the corners to give the water a way to escape. Both options may be pricier than regular solar panels.

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Potential problems with installing solar panels on a flat roof

A key concern about installing panels on a flat roof is the potential for damage to the roof membrane when installing the panels. That’s because tilt racks may need to be fixed into place by using screws that go into the roof itself, and thus risk the incursion of water that’ll damage your roof space and ceilings. If you opt for this solution to your flat roof, ask your installer about their experience in installing racks without causing a leaky roof, including what rectification they offer should a leak occur.

A way of avoiding this risk is to use ballast, which is a fancy way of saying that tilt racks can come with weights that are sufficient to hold the rack and panels down on the roof without screwing them into the roof itself. The amount of weight used isn’t generally considered too much load for most rooves to bear. The downside is that ballasted racks may not be able to be used in locations with high winds, particularly those subject to cyclones. A potential solution for this is that some racking systems use a parapet framework that creates a barrier around the panels on three sides to prevent wind uplift.

Other considerations about solar panels installation on a flat roof include avoiding existing obstacles and structures, such as vents, skylights, exhaust fans and drainpipes. But most solar installers will inspect your property – either in person or virtually – free of charge in order to provide a quote that takes into account the structure and surroundings of your roof.

Read our informative guide on how to choose the best solar panels in Australia

How to optimise sunlight exposure to panels on a flat roof

Considering the above solutions is required because a solar panel being positioned at the ideal angle and direction to catch maximum sunlight is vital to the performance of your solar system. This generally means that the panels should face true north and be positioned at an angle of between 12 and 43 degrees, depending on your location.

As well as the angle and direction of your panels, you can also improve their exposure to sunlight by removing any trees, branches or obstructions that may shade them. This may be tricky given that flat rooves are anecdotally more often shaded by retaining walls or even other nearby buildings. Your solar installer will also be able to advise on what factors to consider before going ahead with installation on your flat roof, including what impact the cost of installing your panels and their efficiency at producing electricity may have on the payback period of your solar investment.

What about maintenance and cost?

Maintaining solar panels on a flat roof is generally easier than on an angled roof because the panels are parallel to the ground and potentially on a single-storey building, making them easier to work on. Cleaning them regularly will help maintain efficiency.

One downside to a flat roof in regard to maintenance, though, is that if you live in an area where it snows, you may have to clear the snow build-up to ensure the panels’ efficiency and prevent undue deterioration.

The cost of installation on a flat roof is often cheaper than a tilted roof simply because it’s easier to access a flat roof – unless you opt for less common frameless or channelled panels. But not all solar installers are deeply familiar with flat-roof installations so it may pay to ask specifically about this issue when you obtain quotes. With the right angle, installation technique, racking system and panel optimisation, you can still get good performance from your solar system and so reduce your electricity bills without too much additional hassle.