Is Your Roof Ready for Solar?

By Cass Jacoby.  

These three questions will help you decide if your roof is ready for solar. 

Demand for solar energy has been steadily increasing over the years, with interest in solar installations jumping to 21% in the first few months of 2020, according to Bloomberg New Energy Finance (BloombergNEF) research. If you are among the many excited to install a new solar system on your roof, then make sure your roof is ready for the project.  

Here are three questions to ask when assessing if your roof is ready for solar: 

1 - Does your roof get enough sun? 

If you are switching to solar power, then you obviously need to make sure those panels will get enough sun to generate energy. The National Renewable Energy Laboratory has some helpful insolation maps that will give you an idea of the amount of sun your area usually gets. You want to make sure your roof gets full sun exposure between 9 a.m. and 3 p.m. all year long, so make sure there aren’t any trees or chimney shadows blocking the light getting to your panels.  

Trimming tree limbs can be a good solution, and even though removing trees is far from being environmentally friendly, the environmental benefits derived by switching to fossil fuel power (from the grid) to solar power (from your solar panels) can outweigh the potential harm of removing a tree. 

Owens Corning suggests making sure your roof slope will maximize sun exposure. Make sure your roof-mounted solar system would be at an angle equal to the latitude of their install location (between 15-40 degrees should suffice for most solar power systems.)  

2 - Does your roof have the right materials? 

Some roof materials are better for solar panel installation than others. Fortunately asphalt shingles, which are rather common, are ideal for solar panels. Solar Power Authority also lists corrugated metal, standing seam, clay tile and rubber roofs as materials that make for any easy installation.  

If your roof is made of slate or wood shingles, your installation will be more difficult. Those materials tend to be more brittle and sometimes can’t withstand the weight of installation. This doesn't mean that you can’t go solar with a cedar or slate roof, there are special mounting components and equipment elements that make it possible to install, but be prepared for a slightly longer and more complex installation if you go that route. 

3 - How old is your roof? 

You will need to evaluate the age and condition of the roof before anything can get installed. 

If you have a brand-new roof, or a roof less than five years old, then this is the perfect time to install solar. The newer the roof the lower maintenance the solar install will be, and the system will age gracefully with your roof over the years.  

Newer roofs are preferable because the average asphalt roof will need to be replaced sooner than the solar system. The average life of a residential solar system is 20-30 years, at the same time, most asphalt roofs only have a lifespan of 20 years. Hence, a roof often needs to be redone entirely before putting on solar panels. 

Don’t worry if you have an old roof though! An old roof is a great opportunity for roofers to coordinate with your solar developer to install the best system overall. 

Middle aged roofs, 8-20 years old, present a dilemma because homeowners don’t want to spend money adding panels to a roof that will inevitably need to be replaced before the solar panels do.  

PV Magazine offers this formula to determine the dollar value of the roof’s age: 

Expected Roof Lifetime – Age of the Roof = Leftover Roof Life 

Leftover Roof Life divided by Expected Roof Lifetime = the percentage of the roof’s remaining value 

Multiply that percentage by the cost of the new roof 

Use the dollar amount calculated above to determine if you are willing to pay for solar. This will help you make an informed decision -- going solar against the cost of a new roof. If the number you get makes you feel a little queasy, then it might be wiser to wait a few years.  

Make sure you consider solar incentives and bank financing rates in your decision too. In some cases it might make more economic sense to replace your roof early so be sure to contextualize the number you get from the formula with other relating factors too.  

Also consider that a roof plays a big role in insulating your home. A new roof will make your home more energy efficient, which may decrease the size (and price) of the solar panel system you need to power your home 

Start the process by getting quotes from both roofing and solar contractors. Compare the total cost of both investments to the long-term electricity savings and you can get a good idea of your projected electricity savings. 

The combined payback period for a new roof and a new solar system will take longer to pay for itself, but a solar power system pays for itself in a way that asphalt shingles and TPO simply can’t. 

Have a question? AskARoofer. 

Find your local roofing contractor in the RoofersCoffeeShop® Contractor Directory.  

About Cass 

Cass works as a reporter/writer for RoofersCoffeeShop and AskARoofer. When she isn’t writing about roofs, she is writing about movies for her master's degree and dancing with her plants.