Can solar be installed on a flat roof?

Fast read

Solar panels can be effectively installed on flat roofs using standard or tilted framing. Ideally, panels should tilt towards the sun, based on the location's latitude, for optimal efficiency.

For instance, Sydney requires a 33° tilt. While panels can be flush-mounted on flat roofs, this approach risks reduced energy generation, increased maintenance, and potential degradation, and could void warranties. Tilted installations use frames or "tilt legs" to raise panels, enhancing solar exposure and improving energy output.

However, the wind load on tilted panels needs consideration, and structural integrity checks are essential. Before installing, consult a professional solar installer to assess the roof and recommend a suitable method. For solar and related products, it's advisable to work with experienced, reputable suppliers or installers to ensure both the system's efficiency and longevity.

Can solar be installed on a flat roof?

Solar panels can be easily installed on a flat roof,. The racking used is similar to the one on a pitched roof which would mean the site flat on the roof , or they can also be installed on an angle as in the picture below – in which case specialised tilt framing is used.

Solar panels work most efficiently when they are tilted to face the sun more directly. The ideal angle for the panels to be mounted is a pitch equivalent to the latitude angle of the location where the panels are being installed. 

So in Sydney, this is 33⁰, Brisbane 27⁰, Melbourne 37⁰, Perth 31⁰ etc. However, with the average pitched roof in Australia being around the 22⁰ mark, this is close enough that no further adjustment in the tilt of panels is required, and the panels on an angled roof are usually installed flat / parallel to the roof surface.

Standard installation on angled roofs

The standard installation process on pitched roofs is for brackets to be fixed to the roof screws on Colorbond roofs or screwed to roof battens on tile roofs. 2 x parallel rails are then connected to these brackets along the roof surface. The solar panels can then be placed and clamped down onto the rail with 4 clamps. 

Recommended installation on a flat roof

On a flat roof, the easiest and fasted way solar panels can be installed is the the same way as above on the roof flat to the roof surface. However, this will result in a relative flat installation, which can have specific consequences. They are:  

solar panels on flat roof
Flat solar panels are typically installed parallel to the roof surface . There are advantages and disadvantages to this approach.
  • Being installed flat to the roof, will result in approximately 13% less annual generation against an installation that is tilted towards the sun. Winter generation will be especially lower due to the low angle of the sun on the panels.
  • Seasonal variation in solar system generation is increased with higher performance in peak summer. On the o the hand the tilted installation will result in a smaller system being able to be fitted, because the tilted rows have to have distance from each other in order to avoid overshadowing each other in the early or late hours of the day. So if for example one can get a 30% larger system on the roof vs a tilted frame version, but then looses 13% of output, the overall generation will actually be bigger with a flat on roof install. Also tilted installs will take longer and cost more. So one needs to weigh up the options.
  • Tilted panels allow for the runoff of rainwater, which cleans a lot of the dust and grime off the panels. Flat installations will require some increased maintenance and cleaning, as the dust will settle a little more. This is not a major issue if the installation area receives a lot of rain, but can increase  cleaning costs in dry and dusty areas. 

Any other issues?

  • Flat panels on the roof can sag in the middle, depending on the built of the panel. This sagging can see increased pooling of water which can create a risk of Potential Induced Degradation (PiD). As well as shading and hotspots created by dust and dirt build-up on the panel glass. Nevertheless as said above some regular maintenance reduce these risks. 
  • Some solar panel models have a minimum tilt recommended by the manufacturer. If this minimum is not met for those specific models, the panel’s warranty may be voided.

How is the framing installed on tilt panels?

The other way to install the panels is by using framing to tilt the panels up on the roof to face the sun. This is similar to mounting the panels flat above but is usually done by attaching “tilt legs” to the rail brackets under the panel as per the photo below. This will raise the modules off the roof surface. The front edge is kept close to the roof surface while the rear edge is lifted up to tilt the panel. Below is the installation process: 

  • Roof Assessment: Like flush-mounted systems, the roof is assessed to ensure its structural capacity meets the requirements.
  • Mounting Structure: The mounting structure consists of long and short  tilted legs designed to hold the solar panels at an optimal angle. These racks/legs are attached to the roof using appropriate fasteners and techniques.
  • Panel Installation: Solar panels are then mounted onto the tilted racks or frames and secured with suitable clamps / brackets.
  • Electrical Connections: The wiring and electrical components are installed and UV resistant conduits run, connecting the solar panels to the home’s electrical system.
Tilt Frames and solar panels
Tilt frames allow solar panels to be positioned at an optimal angle relative to the sun’s position throughout the day and the changing seasons

What else to consider

Tilted racking systems maximise solar exposure, increasing energy production compared to flush-mounted systems. The tilt angle can be adjusted based on the desired energy output and local geographical factors. However, it’s crucial to consider the additional wind load imposed by the tilted panels, as well as ensuring the roof structure can withstand it. On the down side the installed system capacity will be reduced and installation costs can be higher. 

If the panels are installed flat on the roof, then they are less likely to be seen from the ground, which is some instances can create a visual advantage.

So as you can see both parallel or tilted installs on a relatively flat roof can advantages and disadvantages, and both methods are possible. As panels become cheaper and cheaper, the flat on the roof method seems to be employed more and more often, especially with commercial solar installs.

Before proceeding with any solar installation, it’s advisable to consult with a professional solar installer. They can then evaluate your specific roof, its structural integrity, local regulations, and your energy needs. These experts can recommend the most suitable installation method and design a system that optimises energy production. They can also consider the aesthetics and long-term performance  your roof.

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