As people begin the process of researching a potential solar PV system, one of the first questions they ask is “Is my roof even suitable for solar panels?” Solar panels are compatible with most roofing materials, but some are better for solar than others. Read on for EnergySage’s complete guide to determining whether your roof is good for solar.
The best roof types for solar
Solar panels are compatible with most roofing materials, including:
- Metal standing seam: The “standing seams” on many metal roofs make it easy to install solar panels. In most cases, systems can be installed without making any holes in your roof by using mounting systems that clamp onto the seams. Metal roofs are also good insulators and very energy efficient, making homes with metal roofs great candidates for solar.
- Standard clay tile and Spanish tile: Solar installers can work on clay tile roofs easily. Standard penetrating mounts can be used for solar installations on tile roofs, and some companies also produce solar panel mounts that are integrated into a clay or Spanish tile to make installation even easier.
- Asphalt: Solar installers can work on asphalt roofs easily, without worrying about damage. Standard penetrating mounts can be used for solar installations on asphalt roofs.
- EPDM rubber: Ethylene propylene dienterpolymer (EPDM) rubber is used on flat roofs and is most commonly seen on commercial buildings. Solar installers working on flat EPDM roofs use a weighted mounting system (known as a ballast system), which means they don’t typically have to make holes in the roof. For this reason, EPDM installations are usually less expensive than rooftop systems with mounts that penetrate the roof material.
- TPO and PVC: Like EPDM roofs, thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC) roofs are usually flat and use ballast systems to mount the solar panels. TPO and PVC installations are relatively inexpensive.
There are some roof types that less compatible with solar. It is difficult for solar installers to work on slate and wood roofs, because these roof materials are brittle and can break. They require specialized mounting components and equipment because installers can’t walk on the roof without damaging it. This means that installations on slate and wood roofs are more expensive.
Good for Solar?
|Metal standing seam||Residential||Yes||“Standing seams” make it easy to install without drilling holes in the roof.|
|Clay tile||Residential||Yes||Standard penetrating mounts can be used for solar installations on clay tile roofs.|
|Spanish tile||Residential||Yes||Standard penetrating mounts can be used for solar installations on Spanish tile roofs.|
|Asphalt||Residential||Yes||Standard penetrating mounts can be used for solar installations on asphalt roofs.|
|Ethylene propylene diene terpolymer (EPDM) rubber||Commercial, Residential||Yes||Typically flat, and systems can be installed using a ballast system with no roof penetration.|
|Thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC)||Commercial, Residential||Yes||Typically flat, and systems can be installed using a ballast system with no roof penetration.|
|Slate||Residential||No||Slate tiles are brittle and can break easily, complicating the installation process and equipment used.|
|Wood||Residential||No||Wood tiles are brittle and can break easily, complicating the installation process and equipment used.|
Other questions to help you evaluate your roof
The material your roof is composed of plays a large part in your home’s suitability for solar, but it isn’t always the deciding factor. There are a few more questions you can answer to determine whether your home is built for solar.
1. Which way does your roof face?
Solar PV panels are most effective on a broad, south facing roof (at least in the northern hemisphere). Ideally, they should face true south, which is a slightly different direction from the magnetic south you would find with a compass. An easy way to find out if your roof, and thus your property, is good for solar is to look it up on Google Maps. If you show the grid, it will tell you which direction true south is. If you aren’t able to orient your panels to true south, southeast and southwest facing panels will also work and using a rack will help you to get the best orientation. If you aren’t able to manage a southern exposure on your roof, east and west exposures are still possible depending on shading. Even when solar panels aren’t facing directly south, they can still produce significant amounts of electricity, even in locations that don’t receive abundant sunlight. Also, if your roof orientation isn’t the best, you still have the option of mounting your panels on the ground or on another building like a shed or garage.
2. How much shade is there on your roof?
Shade can affect the performance and output of your solar panels so you’ll need to assess how much shade your roof receives and for how much of the day. Shade can be the result of other buildings, your own chimney, or from trees around your house. Your installer can help you to assess the impact of your particular situation. There’s not much you can do about other buildings or your chimney, but you can look into the possibility of removing or trimming trees to create less shade. (Check out “Should You Cut Down Trees to Improve Solar Panel Performance?” for more detailed information).
3. How old is your roof?
Solar panel systems can last for 25-40 years so you’ll want to make sure that your roof is in good shape and won’t need to be replaced in the near-term.
4. What shape and size is your roof?
It’s easiest to install panels on a large square roof. A general rule of thumb is that for each Kw of your system size, you will need about 100 square feet of roof space. Keep in mind, that things like dormers, turrets and skylights will affect the amount of available space.
5. Is your roof flat or sloped?
Flat roofs are fine. If your roof is sloped, the best angle is between 30 and 40 degrees. Keep in mind, that for panels to be self-cleaning, they should be at a minimum of 15 degrees. The maximum angle is 40 degrees (any steeper and performance will not be efficient).
6. Who owns your roof?
At first glance, this seems like a silly question to include. Most people considering installing solar PV own the property where it will be installed. As solar becomes more popular, however, more and more tenants are the initiators of solar installations, encouraging their landlords to consider this option. For tips on how to begin a discussion with your landlord, check out our blog “Can Renters Get In On Clean Energy’s Financial Benefits?”
What to do if your roof isn’t good for solar
There are other solar options available if your roof isn’t ideal for installing a solar panel system, including:
- Installing a ground mounted solar panel system elsewhere on your property
- Building a solar panel carport to simultaneously power your house and provide shade for your car
- Invest in a share of a solar garden, which offers you the benefits of rooftop solar sourced from a large solar panel array in your community
If you shop around and compare your options, all of these alternatives can deliver the same level of savings as you would receive from a rooftop system.