Many U.S. states offer tax breaks, rebates, reduced electrical bills, and other financial incentives for businesses that install solar panels atop their commercial building. Other business owners and commercial building property managers just want to do their part in helping to reduce our country’s reliance on fossil fuels. No matter the reason behind you solar dreams, commercial roofing contractors warn that there are many factors you should consider before installing solar panels.

There are two main types of solar systems in use today. First, there are the traditional, large photo-voltaic panels used in most solar installations. In recent years, certain companies have begun offering miniature PV panels, called solar shingles. Solar shingles haven’t gotten much traction outside of California, so let’s focus on regular solar panel systems first.

Before you even think about installing a solar system, you need to perform a check up on your commercial roof. There are a variety of commercial roofing materials in use today. There’s the common tar and gravel asphalt roofs, there are asphalt shingles (the kind used on residential roofing), metal roofing, new membranes like TPO (that flat, white commercial rooftop), and more. Asphalt roofing usually needs to be replaced every 12 to 20 years on average, and among all commercial roofs, most materials need to be replaced every 17 years.

If you have shingles, your last commercial roofing company probably installed the new layer of shingles right on top of the old roof. But most states have laws allowing a maximum of three shingle layers. If you already have three layers, then your entire roof will need to be stripped.

So what does all this mean for people who want solar systems? If your roof is nearing the end of its life, then you should replace it before investing in solar systems. And yes, replace, not repair. When the time comes to replace your roof, and the time will come, most solar systems will need to be completely removed while commercial roofing contractors do their work. Then, you’ll have to pay for the solar panels or shingles to be installed all over again (on top of paying for a new commercial roof!).

So it’s not so simple as just slapping some solar panels on your roof. You’ll want to be absolutely certain you won’t need commercial roofing repairs or replacement any time soon, or else you’ll be stuck with massive roof repair costs in a few years time.