What is the Best Roofing Material for Solar Panels and Why?

The best roofing materials for residential solar panels are standing seam metal roofing and PVC membrane. Metal panels are the top choice for home solar panel installations on sloped roofs, while PVC membrane is preferred for low-slope and flat roofs.

However, asphalt shingles are, by far, the most common steep-sloped roofing system for home solar panel installations in the US, as approximately 80% of residential roofs are covered with composition shingles.

For flat and low-slope residential roofs, EPDM rubber is one of the most prevalent roofing systems, while Tar-and-Gravel and BUR roofs are more commonly found on commercial roofs. That said, Tar-and-Gravel and BUR roofs can be a viable option for solar deployments on flat roofs, while the situation with an EPDM rubber membrane is a bit more nuanced.

Note: Although, a quality EPDM rubber roof can be a viable option for installing solar panels on a flat roof, it’s highly likely that a rubber roof will require some repairs or even a complete replacement some 10-15 years down the road, while most high-end PV solar panels are designed to continue generating electricity for 25 years. Therefore, going with an EPDM rubber roof for solar installations can be a risky bet, which is why we recommend a quality PVC membrane, instead, because it can last twice as long as EPDM rubber.

In the next section below, we explore top residential roofing materials and explain their suitability for home solar panel installations.

Best Steep Slope Roofing Systems for Solar Panels

Here are the best roofing materials for solar panels on standard residential roofs and why they make our list.

Standing Seam Metal Roofing

There are many advantages to using metal roofing for mounting solar panels.

First, standing seam metal roofing is usually made of steel. And it provides a firm, stable base for solar panel mounting.

Secondly, the solar panels or mounting brackets are attached directly to the raised seams without the need for drilling into the roof deck. This reduces installation time, and it also eliminates the risk of water leaking through penetrations and into the roof deck and framing.

Finally, metal roofing is very durable and long-lasting. This means that you won’t have to replace a metal roof before it is time to replace the solar power system.

Note: One common objection to getting a metal roof in the first place is its initial high upfront cost, which can be as high as $16.00 to $18.00 per square foot installed. The cost can be even higher in the high cost of living areas such as New York, Boston, San Jose, San Francisco Bay area, Los Angeles, Seattle, etc.

Installation Tip: If the coating on metal roofing is scratched through during panel installation, the scratches must be properly re-coated and sealed to prevent corrosion of the metal roof core.

 

Asphalt Shingle Roofing

An asphalt shingle roof is an appropriate foundation for mounting solar panels if it is in good condition. The suitability of asphalt shingle roofs for solar is excellent news for the solar energy industry and for homeowners because asphalt shingle roofs remain the most common residential roofing type.

Best Practice: Replace your Asphalt Roof Before Installing PV Solar Panels

Replacing the old shingles before installing solar panels, makes it most likely that the roof shingles will last as long as the solar panels, so there won’t be the need for removing the solar panels to replace the roof.

If the shingles are not new, your solar installer will inspect them and decide whether panels can be installed without replacement of the shingles. The shingles must be high-quality shingles like those from Owens Corning, GAF, Atlas, and CertainTeed that are backed by a 30-year or lifetime warranty.

The advantage of an asphalt roof vs metal roof for solar panels is that the asphalt roof costs less than metal. So, if you choose to replace your roof before installing solar panels, which again is considered the best practice, your total project costs will be lower.

One slight disadvantage of installing solar panel on an asphalt roof is that shingles and underlayment must be penetrated during the installation to secure the solar panel mounts to the roof deck. Drilling holes in the roof does create a potential risk of premature roof leaks down the road.

To reduce the risk of leaks, specialty flashing is used to create a barrier to divert water away from the solar panel mounts. All possible points of water entry can also be sealed with quality roofing caulk.

However, caulking may present an ongoing maintenance requirement since caulk dries out and cracks with age and persistent sunlight. It must be checked at least annually. If it is cracking or if any caulk is missing, all of it must be removed and replaced.

 

Clay Tile Roofing

There is disagreement over this material because installation costs are high.

Yes, clay tile roofs last 50-100 years, which means that if they are less than 20 years old, they will likely outlast your solar panels.

However, the cost of installing solar panel systems on tile roofing is 35% higher than installation on asphalt shingle roofs, and 50% (or more) higher than installation on metal roofs. This is because the panels cannot be attached to the tiles, and installing fasteners through them is not an option.

Installing solar panels on tile roofs involves removing enough tiles to make space for each panel. Then a mounting foot is installed for each corner of the panel. Each foot is flashed and sealed. Then the panel is installed on it, and tiles are reinstalled around it.

When not installed correctly, solar panels on tile roofing can lead to water damage from leaks. As a result, only consider installers for your solar energy panels that have verified experience with successful installations on tile roofing.

What Roofing Materials Are Not Good for Solar Panels?

Solar installers do not recommend solar panels on wood shake or stone slate roofing.

Not that it can’t be done, and it is frequently done in Europe. However, both materials are brittle and break easily. And it is nearly impossible to install solar panels on a roof without installers walking on the roof in the process.

Another reason is that solar panels should be inspected annually to ensure they are in good condition and sealed against water leaking into the roof deck. A proper inspection can only be done by getting onto the roof and risking additional damage.

Finally, as with tile roofing, installation on wood shake and slate requires invasive and complex methods. More time and materials are needed for installation, and the cost rises. One solar equipment distributor says, “When compared to the installation process with asphalt shingle roofs (or metal), the cost of labor for slate roofs can sometimes be doubled.”

 

Best Low Slope Roofing for Solar Panels

Tar and gravel roofs are the top choice for solar on commercial buildings with flat roofs, aka low slope roofs.

For residential low slope roofing, our experts choose PVC roofing membrane as the best choice for solar panel installation. PVC is also gaining popularity for use with solar on commercial buildings.

 

Tar and Gravel

Tar and gravel roofing provides a stable base for solar. Installation is not overly disruptive to the roof. Tar is an ideal material for sealing penetrations into the roof deck caused by panel mounting equipment.

Installing solar panels on a new tar and gravel roof is preferred, and most of these roofs will last 20-30 years with ongoing maintenance and repairs. So, you likely won’t have to replace the roof before it is time to replace the solar energy panels.

PVC and TPO Roofing

Polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO) are gaining popularity as energy efficient alternatives to asphalt and metal on low slope residential dwellings. They are competitive commercial options too.

Solar panels on PVC and TPO roofs are typically installed with a ballast system to keep equipment in place. This is because penetrating a membrane roof to secure the mounts to the roof deck is not recommended and will void the warranty.

Here is an innovation that enhances PVC as an option:

Mounting brackets for photovoltaic panels are thermally welded to PVC membrane. This eliminates the ballast system and the roof load it causes. There is no need for roof penetrations. And this technology from Dome Solar provides a more stable installation.

Final Tips on the Best Roofing Material for Solar Panel Installation

Light roofing is better than dark roofing for solar, especially in warm climates. This is because solar panels are most energy efficient when the roof is relatively cool – ideally between 60F and 95F. Temperatures above that reduce the output efficiency of the panels by up to 25%. The surface temperature on a black asphalt shingle roof can easily exceed 150F.

Light-colored metal roofing, Cool Roof Rating Council certified asphalt shingles and white or light PVC all reflect sunlight far better than darker roofing colors.

Secondly, the best practice for installing solar panels on any roof is to have your roofing company work together with the solar energy company.

A roofing expert can provide important guidance for installers for that roof type that will reduce the risk of damage to the roof or to the solar equipment. And the collaboration will ensure that any necessary penetrations are properly flashed and sealed at installation – rather than waiting for a potential leak to occur later.