Solar panels for flat roofs: Higher costs, but better savings

Solar panels should never be installed horizontally, but they can go on flat roofs.

Edited by: Emily Walker
8 min read
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Solar for flat roofs.

To maximize your solar panels' time in the sun, they should ideally face south and be tilted between 15 and 40 degrees. Most sloped roofs are in this angle range, which makes installing solar easy. With a flat roof, you'll need additional racking equipment to get your panels at the best angle and direction. As a result, flat roof installations tend to cost more than sloped roof installations.

We'll explain why flat roof solar installations are still worth it and how you can recover some of these costs as extra savings on your electric bills. It's all about the flexibility flat roofs give you in terms of solar panel orientation and angle.

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Key takeaways

  • You can install solar on a flat roof, but you'll need extra mounting equipment.

  • Flat roof installations typically cost more than sloped roof installations.

  • Installations are generally safer on flat roofs, which can lower labor costs despite the higher price tag overall.

  • You can optimize your panels' angle and direction on a flat roof to ensure they stay in the sun as long as possible, which can lead to high long-term energy savings.

If you have a flat roof, you might not realize that solar can work well for your home or business. You'll need more racking equipment to ensure your panels face south and are at an optimal angle. But similar to ground-mounted setups, flat roof solar panel systems aren't constrained by natural roof features, making it easier to get the most out of your solar panels.

The biggest challenge with flat roofs is installer availability. Especially in some areas of the country where flat roofs are uncommon, it may be difficult to find an installer who will add solar panels to a flat roof. A few large national solar leasing companies won't install solar on flat roofs because they work with a limited equipment selection and they standardize system designs to minimize costs.

If you're struggling to find an installer, reach out to EnergySage and we'll see if we can help. By shopping around for a second (and third) opinion, you'll probably find one with experience designing and installing solar panel systems for flat roofs.

You can install solar panels on flat roofs as long as you don't lay them flat. If you do, you'll run into some pretty big issues.

  • Low energy production. In the U.S. and in the entire northern hemisphere, the sun moves from east to west during the day across the southern part of the sky. South-facing solar panels will get the most sunlight. You'll miss out on a lot of electricity production if you lay your panels flat against a flat roof.

  • Dirt build-up. When solar panels are at an angle, dirt can slide off them, or at least wash off when it rains. With a flat roof, dirt will build up much more easily. The dirt blocks the sun, lowering your solar panel system's production.

  • No warranty coverage. Many manufacturers include clauses that void the warranty if the panels are installed flat against a flat roof. Water can pool on top of horizontal solar panels, increasing the risk of water damage.

These problems are all easily avoidable with a flat roof. You just need to install your solar panels at an angle!

Once you find a solar company to perform the work, your flat roof installation should be relatively straightforward. It will probably cost more compared to sloped roof installations, but it will also be safer for your installer and could help you save more money over time.

Why do flat roof installations cost more?

As we've mentioned, solar panels on flat roofs generally require specialized racking equipment to get them at the right orientation and angle. Instead of simply laying solar panels flat on a sloped roof, your solar installer will likely use angled mounts. These mounts tilt your solar panels, exposing them to the sun for as much of the day as possible. The extra equipment typically results in a higher price tag for flat-roof solar panel systems.

Why flat roof installations are usually easier and safter

Despite higher costs overall, labor is often cheaper in flat-roof installations. Labor and installation typically make up about 10% of solar installation costs. Installing solar on a flat roof is much easier and safer for your solar company compared to sloped roofs. Workers can move freely on the roof without special equipment and most of the roof materials used on flat roofs can easily handle the wear and tear.

Your solar installer also won't need to make roof penetrations to install flat roof solar panels. Sloped roof solar installations typically use "penetration mounts." In these mounting systems, installers affix racking equipment to your roof by drilling multiple holes. Instead, flat roof systems often use a weighted mounting system called a "ballast system," which uses gravity to keep your equipment in place.

Just to be clear, we still recommend having professionals install your solar system rather than attempting a DIY project.

How to get more solar power and money out of a flat roof

Ideally, solar panels should face south at an angle equal to their latitude, about 15 to 40 degrees. East- or west-facing systems are also generally fine but will produce less electricity. Some sloped roofs are steeper than others, which can also lower electricity production. Solar can still be worth it with these setups, but your electric bill savings will be lower than if your solar panels were oriented ideally.

Flat roofs offer more flexibility in terms of your solar panel system design. You can orient them to face south and mount them at the optimal angle to maximize your solar energy generation. Solar panel systems on flat roofs often perform better than those on sloped roofs, resulting in better long-term savings.

If you live in an area where many properties have flat roofs, your local installers will likely have experience working with them. We still recommend getting multiple quotes to ensure you're working with a company with the right expertise and background.

The best way to find multiple local solar installers is to register your property on the EnergySage Marketplace. When you sign up, you'll input your property address, which will let installers know that you have a flat roof. Solar companies willing to perform your installation will send you quotes that you can compare based on price, reputation, and equipment. If you have any questions along the way, reach out to your free Energy Advisor who will help you go solar with confidence.

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  • 100% free to use, 100% online
  • Access the lowest prices from installers near you
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