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?”
Here are a few key considerations that can help you to answer that question.
Evaluating Your Roof, Asking the Right Installation Questions
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 about your property 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 PV system 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 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. What is your roof made of?
Solar panels are compatible with most roofing materials including composite, wood shake, cement tile, tar and gravel, or metal. Slate and clay tile roofs can be prone to breakage so make sure that you have an experienced installer if your roof is made of these materials.
7. 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?”
For more information on where to install solar, check out our Solar 101 section here.