There are plenty of benefits to going solar for homeowners. However, it’s not always feasible for everyone. First and foremost – having a roof that can support solar panels is mandatory. So, how can you tell if your roof is good for solar?
This can easily be determined by asking the following four questions:
- How many solar panels do I need?
- Does my roof have enough space for solar panels?
- What material is my roof made of?
- Will I need to replace my roof in the next 25 years?
This might feel like a lot to unpack on your own, but have no fear! In this article, we’ll take a deep dive into these questions in hopes of helping you find out if your roof is suitable for solar.
How many solar panels do I need?
Before determining whether your roof can accommodate solar, you need to know how much physical space the system will take up.
When figuring out how many solar panels you need, consider these three factors:
- Your energy usage: More energy consumption demands more panel space, more efficient panels, or more sunlight.
- Sun exposure: If your home gets a good amount of direct sunlight, you can get away with fewer or less efficient panels.
- Solar panel efficiency: More efficient panels mean that you will need fewer of them because they are better at converting sunlight into energy relative to less efficient panels.
Once you arrive at the number of solar panels you need, you can finally estimate the square footage your solar energy system will occupy.
Take the typical solar panel size – 17.55 square feet – and multiply it by the number of solar panels you need. The result approximates how many square feet your solar system will take up.
For reference, a typical home in the United States needs 19 to 23 solar panels to cover its energy bills. That's between 335 and 405 square feet.
Therefore, a home requiring 19 to 23 solar panels needs at least 335 square feet of roof space.
For a more in-depth look at how to calculate how many solar panels you need for your home, click here.
How much space does my roof have?
If your roof doesn’t have enough space, it’s not suitable for solar panels.
This concept might seem like a no-brainer, but it’s crucial to know your roof’s measurements beforehand. Given a typical roof measures around 1,700 square feet and an ordinary solar system needs no more than 405 square feet, it would seem most roofs make the cut four times over.
However, you won’t be using all that space. Penetrations like chimneys, skylights, and vents obstruct solar panels. Additionally, panels can’t go across ridges and valleys, which further limits the usable space on your roof.
Solar panel systems also don't work as well without direct sunlight. Even if you have bountiful space, solar panels in shady areas or on a north-facing roof will produce less power.
Less-than-optimal sunlight won't take you out of the running for solar, but keep in mind that you may need more panels (and roof space) than your initial estimate.
How to measure your roof
The most accurate way to measure your roof entails climbing up there with a tape measure.
This roof estimate tool, which factors in skylights, vents, and dormers, delivers an accurate enough estimate for the cost of a roof replacement.
Once you take your measurements, compare the square footage figures between your roof and your solar system.
Your roof will suffice as long as you have more space than the estimated square footage your solar array will occupy.
If you have enough space, but the numbers seem too close for comfort, look to install solar panels with higher efficiency to make up for the lack of space. These panels produce more power per square foot, which means you can fit the system you need in a smaller area.
If you can’t make the space room for rooftop solar, consider ground-mount solar panels and community solar programs.
What is my roof made of?
Installing solar should present minimal risk to your roof integrity and warranty as long as you hire a solar company experienced with your particular roof material.
Despite this, your roof’s material can impact your solar installation's time, complexity, or damage potential.
Since most contractors know how to install panels on asphalt shingles – the most common roofing material in the United States – the process is streamlined and the chances of costly mistakes diminish.
If you install solar on composite (aka synthetic) roof shingles, you may run into some issues. Installation requires drilling holes through the shingles and into the rafters to fasten the solar mounts to the roof. If not flashed and sealed correctly, unwanted leaks and premature roof failure can occur.
For this reason, metal roofs, particularly standing seam, are the material of choice for solar. Installers don’t need to poke holes into the roof to fasten panel mounts. Instead, they use clamps or brackets to latch onto the seams. This will not only keep your roof structure intact but also speed up the solar installation process.
Concrete, slate, and clay tiles, on the other hand, are less ideal for solar. For starters, the brittleness of these materials makes for a risky installation process for your solar panels, roof structure, and the workers installing them!
The headaches and liabilities are partly why some solar installers avoid working on tile roofs. If you manage to locate an installer who is willing to install on a tile roof, they then must work slowly and deliberately to avoid damaging tiles, which only adds to costs.
Wooden roofs are arguably the worst for solar installations, at least from a safety standpoint. Not only do wooden shakes easily split when walked on and drilled into, but they also pose a fire hazard.
Solar panels catching on fire is exceptionally rare, but not impossible. At that risk, it’s better to be safe than sorry, and having a wooden roof would be the worst-case scenario.
Is my roof due for a replacement?
Since well-maintained solar panels can perform beyond 25 years, we recommend ensuring the underlying material will last at least as long.
You very well could replace a roof with solar panels installed. However, the process requires more time, money, and logistics than necessary. Installers essentially need to remove and re-install the system before and after the roofing job.
Imagine putting a brand-new granite surface on top of shoddy kitchen counters. You could transfer the countertop over for when you inevitably replace the counters, but doing the full remodel first would have been far more time and cost-effective.
Roofs with more than 25 years of life left get our seal of approval for a solar installation. If you’re unsure about this, you can get a roof inspection from a professional for a reliable answer. If you know when you had your roof installed, you can also subtract its age from its expected lifespan for a rough estimate
Is my roof suitable for solar panels?
In a time when the benefits of going solar are too tempting to ignore, there are a few compelling reasons to not go solar – or rather why solar isn’t necessarily right for you.
Having a roof that is suitable for solar is 100% a dealbreaker.
Therefore, homeowners should confirm whether their roof can house solar panels by calculating their system size and measuring how much roof space they have to work with.
You can also save yourself the hassle by putting your home’s address into our solar calculator, which estimates your home’s solar potential based on your electric bill and geographic location.
With a firm grasp of your future solar savings, if or when to install a new roof is the final item to consider.
Key takeaways
- Determining whether solar will suit your roof comes down to solar potential. It's important to have a large enough roof to fit the amount of solar panels you need.
- Traditional asphalt and metal roofs are the best materials for solar projects. Solar installations are riskier on tile or wooden roofs.
- If you do not have a roof suitable for solar, alternatives to roof solar include ground-mounted and community solar.
- Roofs with more than 25 years of life left are best for solar panels.
Maira Deardon
SolarReviews Blog Author
Jack Wisniewski is a writer and researcher at SolarReviews. When he’s not guiding readers towards their optimal roofing decisions, you can find him working out or watching professional soccer.