Solar Panels On A Flat Roof??? Yes. Here’s How.

solar panels on flat roof

As renewable energy becomes more affordable, it becomes more and more ubiquitous. We have arrived at a point in time where it isn’t easy to cruise through just about any neighborhood without seeing at least one solar panel.

While any building can benefit from installing solar panels, some people may wonder if their roof might not be a viable candidate for housing the panels. These would be the people with flat roofs on their buildings.

Can You Install Solar Panels on a Flat Roof?

Not every building has an A-line roof, and there are those of us out there who’ve had the audacity to build ourselves a building with a flat roof. While it looks great, and it’s something different, a flat roof can present a few obstacles to features common to many other buildings.

You can install solar panels on a flat roof, but to do so, you’ll have to make some adjustments that your pitch-roof owning neighbors wouldn’t. But it’s possible, and by installing solar panels on your roof—flat or otherwise—you can do a lot to cut down on your utility bills and help even a little bit in the quest to preserve the environment.

Three Ways to Install Solar Panels on a Flat Roof

Whenever people figure out a way to do something, other people surely come up with alternate solutions. Solar panel installation is no different, even when regarding a flat roof. Each method has its pros and cons, and each approach may or may not work with your particular roof due to the construction features you have, but a best way exists for you and your building.

Attached

Installing solar panels by attaching them involves drilling into the roof and connecting them directly to the structure. However, attached mounts go beyond just screwing some bolts into the roof and hoping for the best.

Once installers drill into the roof, they apply a chemical anchor, filling the holes. Once it has set, the chemical anchor serves to exert a firmer hold than just driving wood screws into the roof decking or support beams would provide.

Ballasted

As the name implies, ballasted installation relies on weight—in this case, usually concrete bricks or blocks. The panels themselves rest in a series of trays, and those (usually) metal trays also support the concrete blocks. These blocks apply the weight that holds the panels down and in place on your roof.

The big plus here is that ballasted installation does not require drilling into the roof. As we’ll see later, drilling into a flat roof for any kind of installation can potentially create issues with leaks. These can end up damaging more than just your roof but can extend to cause problems with your walls, carpets and other flooring, or your furniture and personal belongings.

In areas where high winds are an issue (think Oklahoma, where the winds come sweeping, etc.), installers may utilize a hybrid ballast installation. Some portion of the system depends on drilling and getting anchored to the roof. 

While this hybrid method does negate some of the positive aspects of the ballast installation not requiring any penetration of the roof, it also vastly reduces the chances that your panels will blow away during a severe weather event.

Concrete Footing or Foundation

For some roof installations, the home or building owner may not have the option of drilling into the roof. There may be insurance issues at hand, or perhaps a concrete roof prevents it. In that case, concrete footing installation is a good solution. 

Installers attach concrete blocks to the roof in question and then attach the solar panel racks. There is no compromise of the roof in this case. 

Concrete footings often get used on a flat roof with parapet walls surrounding them. Since the parapets will cast shadows, if your panels lie low enough, shadows will interfere with their efficiency. Concrete footings can raise the panels, and that added elevation addresses the issue of parapet shadows.

Footings also help ensure the panels do not get upset by severe weather. Barring the devastating power of a tornado, panels installed on concrete footings are better suited to survive the high winds of a serious rain or windstorm. 

Read More: Best DIY Solar Panels That You Can Buy Right Now

Costs of Installing Solar Panels on a Flat Roof

About ten percent of your total solar panel system and installation costs will go to labor. While some aspects of a flat roof installation may be more expensive than a pitched roof, these costs may be offset by the relative safety of working on a flat roof.

Installers working on a pitched roof are much more likely to fall than on a flat roof. This can lower insurance costs for the installation company, which one would hope would translate to savings passed on to the customer. 

Depending on many factors, the average cost of installing a solar panel system on a flat roof will run in the low five figures, up to about $15,000 before federal tax credits. Those factors include:

  • Number of panels
  • Type of mounting system employed
  • Batteries for power storage

Installers may also face issues specific to the roof in question that could complicate things, making installation more expensive. However, all told, installing on a flat roof will almost always incur comparable costs to installing the same on a pitched roof.

Are There Any Disadvantages?

There are, indeed, disadvantages to installing solar panels on a flat roof. However, almost all of them can be managed so that they don’t cause problems or can be completely overcome. After all, if you’re going to pay what you’ll have to pay for a solar panel system, you need it to work well and not cause problems. 

These can include the pooling of water and leaks that often follow that. Dirt and debris can significantly diminish the panels’ efficiency, and actual flat installation may not be an option. Let’s explain.

Read More: Best Looking Solar Panels You Can Buy Right Now

Pooling Can Cause Leakage

Not many flat roofs are actually flat. Most of them have a pitch of a few degrees to allow for water runoff to keep water from pooling. However, with solar panel installation, the weight of the units could put a kink in the water drainage by creating minor deviations in the roof’s pitch. 

Maybe the roof installation gets compressed by the panels’ weight, or perhaps drilling into the roof has interrupted the slope. No matter the reason, pooling can be an issue, and if you discover it, you need to deal with it as soon as possible.

Water allowed to pool on a roof for more than 48 hours can lead to issues, which we’ll get to in a moment. But it’s important to note that in the roofing industry, the term is “ponding.” By definition, that water has stood on your roof for 48 hours after a rain.

If water stands for several hours, problems won’t likely arise, as roofing materials are manufactured with water resistance as a part of their construction. However, even the hardiest materials will eventually succumb to water damage. Remember that water is the only universal solvent. Sure, every living thing needs it to survive, but it will ruin anything given enough time to do so.

Pooling can lead to leaks in your flat roof, and as we mentioned earlier, leaks can cause all sorts of damage. Having your solar panel installation done on your flat roof by professional installers rather than relying on Uncle Cletus and his can-do attitude will go far in ensuring you avoid roof damage or other problems that arise from pooling water and roof leaks.

They Get Dirtier

A great advantage to having your solar panels on a pitched roof is that rain, dust, and dirt roll off the panels much more easily than they would without a slope. Since solar panels need as much sun exposure as possible to work at maximum efficiency, the dustier or dirtier your panels get, the worse they’ll function.

Finding solar panels on a flat roof that have been installed to lie completely flat is difficult because even flat-roof panels usually get installed with at least some slant to them—even if it’s only three or four degrees. This allows rainwater to drain off the panels, and any dust on them will roll off with it.

But since panels on a flat roof will almost always sit flatter than those on a pitched roof, they will never shed water, dust, dirt, or other debris as efficiently.

Read More: How To Clean Solar Panels?

You Might Still Need to Tilt the Panels

We just mentioned the slight tilt in almost any flat-roof installation, but in this case, we mean a more severe tilt. Earlier, the idea of parapets came up. Depending on how high they might be, you may need more of an angle to your panels. 

You may also need to tilt your panels to maximize the use of space on your roof. If you do not have enough space on your roof relative to the number of panels you need, tilting the panels will free up some space since a tilted panel will take up less space than a flat one.

FAQs

Solar power installation brings a lot of variables from site to site, so it’s difficult to answer every question that may come up. Still, here are a few of the more common ones that come up regarding solar panel installation, specifically on a flat roof.

  • Is solar panel output lower with a flat roof?

    No, solar panel output is not lower with a flat roof. While you’ll need to orient and angle your panels so they’re as south-facing as possible, tilting panels on a flat roof isn’t difficult. And as we’ve already discussed, no matter the pitch of your roof (or lack thereof), your panels will more than likely sit with at least some incline, even if it’s only a few degrees.

    You may even get a more efficient angle with flat-roof installation since you can control the amount of pitch your panels have better than on a more traditional home roof with peaks and slants that might be more severe than is best for your panels.

  • Is solar panel output lower with a flat roof?

    No, solar panel output is not lower with a flat roof. While you’ll need to orient and angle your panels so they’re as south-facing as possible, tilting panels on a flat roof isn’t difficult. And as we’ve already discussed, no matter the pitch of your roof (or lack thereof), your panels will more than likely sit with at least some incline, even if it’s only a few degrees.

    You may even get a more efficient angle with flat-roof installation since you can control the amount of pitch your panels have better than on a more traditional home roof with peaks and slants that might be more severe than is best for your panels.

  • Do flat roofs require specialized solar installers?

    While you probably don’t want to hire someone who has never installed solar panels on a flat roof before, the truth is that most qualified solar panel installers will be equally comfortable working on sloped or pitched roofs. They may be more at home on a flat surface simply because it’s statistically safer than working on a pitched roof.

  • Do panels always need to be tilted on a flat roof?

    Your panels will need to be tilted no matter the angle of the roof on which they sit for several reasons. Because of the tilt of the earth’s axis relative to the sun, as we orbit our star, the sun’s rays hit us at different angles at different times of the year.

    This explains why the sun, in winter, appears to sit lower in the sky than it does at the same time on a summer day. At high noon in summer, the sun is in a much different spot than high noon in December.

    But no matter the time of day, homes in the northern hemisphere get the most light from the sun on their south sides. So all solar panels in the northern hemisphere need to face south to work best, just like southern hemisphere panels need to face north. This facing refers to the tilt of the panels.

    You can lay your panels flat, but you’ll get much more efficiency from them by tilting them. How much? The number of degrees of tilt equals your latitude. Houston, Tex. sits at a latitude of 29.7° N, so panels in that city will work best when tilted toward the south at about 30°. Portland, OR residents live at 45.5° N latitude, so their panels will work best when tilted at 45°.

  • How many solar panels do I need for a flat roof?

    The number of panels you need in your solar power system has nothing to do with the pitch of the roof. Instead, you’ll need to:

    Figure the number of kilowatt-hours your home requires.

    Calculate how many kilowatt-hours you can expect a solar panel to generate in your area of the country.

    Decide on the size of solar panels you wish to install.

    Do the math.

    This formula applies whether your roof is flat or boasts the steepest of pitches.