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Solar Panels On Flat Roofs

By Benjamin Strusnik March 15, 2022

Solar Panels On Flat Roofs

The typical home has a slanted roof, whether it’s covered in shingles, tiles, or made of metal. It’s probably the most common roof you’ll see anywhere. 

Although some of us live under a flat roof, would it still be possible to install a solar panel on a roof like this? And do we need to know anything else about flat roofs before we commit to a solar system? 

We did research on all the important details. Check out what we’ve put together to help you get a better understanding of what installing solar panels on a flat roof involves. 

Is Solar Panel Installation Possible on a Flat Roof?

Yes, absolutely. A flat roof is just as good as an angled roof as long as your roof is in good condition and there’s nothing getting in the way of the sun’s rays.

In some ways, a flat roof is even preferable to a slanted roof. For one, it’s more aesthetically pleasing as the panels are harder to see from the street. Sitting flush against the roof hides it from view.

When installing a solar system onto your roof, you have the choice between two different methods of mounting the panels. One is mounting the solar panels flat against the roof, and the other uses specific mounting equipment to keep the panels tilted at a 25° angle. 

While mounting the solar panels flat against the roof sounds like the easier and faster option, there are a few things that’ll have you consider.

Why Do I Need Special Mounting Equipment?

Having the solar panels angled allows for more exposure to the sun and, therefore, increased energy output. While there’s nothing wrong with lying solar panels flat, this is the main reason for getting special mounting equipment.

There’s a lot of specially-made equipment that’s used to tilt the solar panels upward. They cost a little more than the usual mounting rigs.

can I install solar panels on flat roofs

A sloped roof made of shingles needs a special solar panel shingle roof mount to safely secure the panels. 

Installing solar panels on a metal roof doesn’t need any special equipment as they are fixed to the roof the same way most other solar installations are done. 

Some of the metal roofs that you can buy are made from recycled material which is a good combination to use with solar panels. 

Metal roofs that are coated with reflective paint have been shown to help keep homes cooler during the summer months. Installing panels on a metal roof like this is going to lower the energy usage on indoor cooling that would normally be taken up by things like air conditioners and fans.

This combination of solar panels and metal roofs can actually boost energy efficiency and reduce the utility bill. 

Is Output Impacted with a Flat Roof?

As long as the solar panels get enough exposure to the sun, their efficiency won’t be impacted. A flat roof can offer a few more options than a slanted roof, too.

The direction that the roof is facing and how it’s angled can have an impact on solar panels that are mounted onto a slanted roof. A flat roof makes it easier to point your solar panels in any direction and also tilt them to receive the most sunlight.

Flat roofs let you optimize the total energy output of solar panels. In the northern hemisphere, you can mount the panels so they can face the south and also adjust their tilt according to how far above sea level your house is.

A slanted roof that faces east or west can have solar panels installed but it becomes tricky if there’s only space enough on the northern side of the roof. 

can you install solar panels on flat roofs

This isn’t good for the solar panel’s energy production on a day-to-day basis because you want the solar panels to face south as much as possible. Having the solar panels face south exposes them to a lot more sunlight than if they're on the northern side. 

Slanted roofs can also be too steep for ideal electricity production. The steep angle means that it won’t get enough exposure when the sun is directly overhead during the day.

A flat roof allows your solar panels to do their job for longer while guaranteeing maximum power delivery for many years.

Is It More Expensive to Install Solar Panels on a Flat Roof?

Compared to the actual panels and other pieces of equipment you need, labor and installation make up the smaller part of the installation budget. 

An entire solar power system can cost anywhere between $10,000 and $25,000, while installations can range between $18,000 and $9,000 depending on your region. 

installing solar panels on flat roofs

Sunny regions are less expensive while colder regions cost more. 

It also depends on how your solar panels are installed; whether you’re doing it on your own or hiring contractors to come and do the installation for you. 

Labor and installation usually involve climbing on top of your roof to mount the solar panels. A steep roof makes this harder to do. 

By comparison, a flat roof is much simpler to work with. It’s easier for workers to move in and around the installation area without using any special safety equipment. 

Not to mention, the build materials used on flat roofs are strong enough to handle the wear caused by installation. 

Installing solar panels onto a flat roof also means that you won’t have holes bored into your roof. Unlike sloped roofs that usually need to use what’s called a penetration mount. 

A penetration mount needs several holes to be drilled into your roof to hold the solar panels. A flat roof uses a ballast system, which is another way of saying “Weighted mounting system.” 

A ballast system essentially uses the strongest force to hold it down onto the rooftop, also known as gravity. So, there are no holes that need to be drilled. 

Are There Any Risks Involved?

While we know that installation is safer on a flat roof, other issues could come up. It’s not unheard of to hear that solar panels damage your roof, however.

The first thing you’ll notice is dirt builds up a lot quicker when the panels are lying flat. This includes dust and other debris carried by the wind, like leaves. These stay behind long after the rainwater or morning dew evaporates. 

In 2009, Google - yes, Google - did some research of their own and found that their flat-laid panels’ energy output was halved 15 months after their initial installation. Their tilted solar panels did far better.

This is because tilted panels can usually be rinsed off by the rain; water washes the dirt away and it runs down the side of the panel. 

Leakage is the worst problem that comes with flat roof installations. Panels that are installed lying flat are more likely to pool water on top and around them when it rains. This can cause damage to your roof. 

The best way to avoid water pooling is to have your panels be tilted. At the very least panels should be fine when they’re tilted 4° or 5°. As long as the water runs off of the solar panel, you’re good to go. 

Some additional measures can be taken during the initial installation process. 

One method does need to be done by putting holes into your roof, unfortunately. By drilling a few holes and fixing the panels directly to your roof you’ll be able to reduce the risk of pooling. 

A ballasted system also works well. Weights are used to anchor the panels instead of drilling screws in place.

What Are the Pros & Cons of a Flat Installation?

There are a few ups and downs to think about before committing to a full-on solar system installation. We’ve just read about water pooling and dirt build-up a little while ago, there’s some more that we haven’t covered, yet. 

how to install solar panels on flat roofs

Let’s take a look and see whether a flat roof is actually the best roof for solar panels. Some of these points have already been mentioned.

Pros

  • Aesthetically pleasing. You won’t see the roof filled with panels from the street;
  • Flat roofs are more versatile allowing the panels to be mounted in almost any way; 
  • A flat roof is generally safer to work on, so doing maintenance goes much smoother;
  • Flat roofs expose the solar panels to more sunlight;
  • Installation and labor costs can be more affordable if you choose to lay the panels flat against the roof.

Cons

  • Solar panels lying flat get dirtier faster, reducing energy output.
  • Flat-laid panels aren’t exposed to the sun as much compared to being tilted up.
  • Laying the solar panel flat can risk voiding the warranty of the panel. This is because of the water that pools on top of the panel. Water can get in-between the frame and glass coating of the panel. Essentially, years’ worth of water could seep into the electrical components. 

Conclusion

It’s completely doable to install solar panels on a flat roof. In some respect, a flat roof provides a lot more flexibility and practicality compared to a slanted roof. 

Labor and installation can be a little more affordable, your roof won’t necessarily need any holes drilled into it, and flat laid solar panels won’t affect the look of your home. 

On the other hand, you do need to think about the issues you could face. Water pooling up, the panels get dirtier much faster, and they could be less exposed to the sun if they’re not tilted. 

Going with a tilted mounting system does add a bump to the budget, although when you’re running the risk of cutting your solar panels’ life expectancy in half, we’d gladly pay a little extra to get them tilted up. 

In the end, these are just things that you should consider before going all-in. Better to be safe than sorry, right?

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