Solar Panels on a Flat Roof: 5 Things to Know

Can you install solar panels on a flat roof?

Yes, you can successfully install solar panels on the flat roof of your home or business. However, there are some challenges to be aware of.

Flat roofs have a minimal slope allowance that will accommodate solar PV panel systems. A roof having a rise of 0.25 inches over a 12-inch run — known as a 0.25:12 pitch roof — is considered a flat roof. These roofs are also commonly known as:

• Low pitch roofs
• Low slope applications

Flat and low pitch roofs do provide some challenges for installers, but there are a number of solutions to adapt a solar system to unique roof types.

Skip to 12:15 to hear Rex and Patrick discuss the main solar solutions for different kinds of flat roofing on Solar.com LIVE!

The challenges of installing solar panels on a flat roof

The key to a successful flat roof installation is identifying obstacles early in the process. Here are some structures to consider before installing solar panels on a flat roof:

• Drains
• Vents
• Exhaust fans
• Rooftop units
• Curbs
• Parapets

The key to overcoming these challenges is identifying them early on and choosing an experienced installer that can confidently navigate them. With hundreds of carefully vetted installers and dedicated Energy Advisors, the solar.com marketplace is a great place to start.

5 things to consider when installing solar panels on a flat roof

1. You can install solar panels on a flat roof

Installing solar panels on a flat roof takes a little extra consideration, but you can do it! There are a number of flat roof mounting techniques available on the market to accommodate your roof, and an expert energy engineer can to get you on the right path to a successful solar panel installation.

Your main concern as a homeowner is to find an experienced and reputable installer to handle the job!

2. Costs are on par with the typical pitched roof

Not only are flat roofs a viable solar electricity producing surface, but the cost can be on par with that of standard sloped roof installation. Use this solar calculator to get a ballpark of how much solar would cost for you home and how much you can save by going solar.

3. Your solar panels may or may not be tilted

When installing solar panels on your flat roof, the resulting product can be tilted or not. There two main factors in the design of a successful solar panel system generating maximum electricity:

1. Solar panel tilt angle
2. Solar panel orientation

An optimum tilt angle and orientation of your solar panels on a flat roof will ensure top energy production performance of your system. Only top manufacturers give warranties on panels installed at an angle of fewer than two degrees.

Although these warranties exist and make sense in some situations, you’ll need to weigh the production difference when installing your solar panels horizontally – or near horizontally.

4. There are higher risks for leakage because of pooling

Compared to standard sloped roofs that direct water to eaves and gutters, flat roofs tend to collect water in certain areas. This is known as pooling or ponding.

Even without solar panels, pooling poses a risk of leakage and water damage to your home. So this may be something to address before going solar.

Pooling increases the risk of water leaking into the drill holes used to mount solar systems — it’s just the nature of the beast.

While pooling and leakage are are certainly something to consider, there are options for minimizing this risk. Instead of drilling into the roof to attach the solar panels, installers can use ballast (weights to keep the solar system in place) or a combination of ballast and drilled attachments to reduce the number holes and the risk of leakage.

Optimal energy performance can be achieved through any of these flat roof solar panel installation methods. However, it’s important to raise this concern early in the design process.

5. Solar panels on flat roofs may require frequent cleaning

Solar panels on a standard pitched roof tend to clean themselves when precipitation washes down them. In fact, just a slight degree of tilt – 3 to 4 degrees – can help keep solar panels clean when it rains.

However, flat panels tend to collect water, dust, and debris, which can reduce electricity generation by up to 10 percent. So if you install entirely flat solar panels, you’ll need to perform more frequent cleanings to maximize your generation and savings.

That’s not the end of the world. Solar panels can be cleaned with a quick dusting, spray of a hose, or wipe of a squeegee.

However, if you’d rather not spend more time cleaning your panels, raise this concern early in the design process.

Related reading: How To Choose Solar Panels for Your Home

How to find solar panel installers for a flat roof

As we’ve mentioned throughout the article, the key to successfully installing solar panels on a flat roof is finding an experienced and reputable installer to do it.

Solar.com is a free online marketplace offering potential the best pricing quotes from a carefully-vetted network of installers. In fact, we accept just 30% of solar installers that apply to join our network (we’re that picky).

Through the solar.com marketplace, you’ll be paired with a dedicated Energy Advisor that will help you:

• Design a solar system that meets your goals
• Find qualified solar installers in your local area
• Compare quotes, equipment options, and warranties
• Line up financing options
• Take advantage of federal, state, and local solar incentives (like the 30% federal tax credit!)

Start a solar project today with multiple quotes from vetted installers.