1) How old is your roof?
Solar panel systems can last for 25-35 years, so you'll want to ensure that your roof is in good shape and won't need to be replaced soon. If your roof is near the end of its lifetime, it's worth waiting to go solar until it needs a replacement. If your roof is already in good condition, great! Solar panels can help extend the life of the portion of your roof that they cover.
2) What is your roof made of?
You can install solar panels on nearly any type of roof, but certain materials are easier to work with than others. Due to their brittle nature, slate, and wood are not recommended to support a solar system.
Metal standing seam: The "standing seams" on many metal roofs make it easy to install solar panels. In most cases, you can add solar panels without making any holes 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.
Asphalt: Solar installers can work on asphalt shingle roofs easily without worrying about damage. Standard penetrating mounts are the norm here.
Standard clay and Spanish tile: Solar installers can easily work on clay tile roofs with standard penetrating mounts. Some companies also produce solar panel mounts that integrate into a clay or Spanish tile to make installation easier.
EPDM rubber: Flat roofs often use ethylene propylene diene terpolymer (EPDM) rubber, and solar installers can work with it. They'll use a weighted mounting system (known as a ballast system), so 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.
3) How big is your roof?
It's easiest to install panels on a large, squared-off roof. But even if you have limited space, you can look into installing a smaller number of high-efficiency panels to produce as much power as possible with the area you do have available.
A general rule of thumb is that for each Kw of your system size, you will need about 100 square feet of roof space. Remember that dormers, turrets, plumbing vents, chimneys, and skylights will affect the available space.
4) Is your roof too shady?
You could have the biggest roof in the world, but if you live next to tall buildings or trees that shade your roof all day, it's not a good fit for solar panels. An experienced installer can figure out what makes sense for your house just by looking at satellite images.
5) What is the angle of your roof?
Generally, between 30 to 45 degrees is the optimal tilt (also referred to as roof angle or azimuth) for most solar panel systems. Thankfully, that's the angle of most standard roofs in the United States. Solar panels on a steep roof generally produce less electricity and are more challenging to install. Installing solar panels on a flat roof typically requires more space and makes more sense for larger installations where it's practical to add racks that create optimal panel tilt (like on top of factories).
6) What direction does your roof face?
Your roof's orientation, or the direction your roof faces, impacts how much electricity your solar panel system will produce. Ideally, you want your solar panels to face south to receive the most exposure to sunlight.
Solar panels are most effective on a broad, south-facing roof. Google Maps makes it easy to figure this out. Ideally, the roof should face True South, a slightly different direction from the magnetic South you would find with a compass. But Southeast and Southwest-facing panels will also work well. If your roof orientation isn't the best, you can still mount your panels on the ground or another building, like a shed or garage.