This is an excerpt from the May 2018 edition of The SOL SOURCE, a monthly electronic newsletter analyzing the latest trends in renewable energy based on our unique position in the solar industry. To receive future editions of the journal, please subscribe.

For the general public, “rooftop solar” generally brings to mind a small residential solar array like the one people see while driving through the neighborhood. But, rooftop solar is not limited to the residential space. It also encompasses expansive solar energy systems spanning tens of thousands of square feet on a flat commercial rooftop, like the ones employees of the solar industry gaze at longingly through an airplane window every time we are close to landing.

Large rooftops on warehouses, offices and other buildings across the nation, where 60-65 percent of rooftop area is suitable for solar, represent gigawatts of potential solar build. However, for facility managers being pitched to install solar, the prospect of a significant electric generator on top of their asset raises many questions and concerns, which generally have simpler answers than they may think.

Trust the Process

In initial conversations, many commercial customers, namely facility managers, worry about the impact that the added weight of a solar array may have on the integrity of their roof. These concerns are valid, which is why developers conduct a thorough assessment of the roof’s structural strength to determine the safest way to install a solar array, analyzing the roof framing plan and original construction drawings.

Age Isn’t Everything

As the saying goes, [rooftop] age ain’t nothin’ but a number. Before structural analyses are made, it’s common to hear from customers who think their roof simply too old to house a solar array. While in some cases a roof’s age can be a preventative factor, many older roofs are actually better-built for solar. In past decades, structural engineers were unable to accurately calculate roof strength, and therefore overbuilt the roofs to be safe. Today’s solar engineers can take advantage of this when adding the weight of the solar energy system.

Newer standing-seam roofs generally are the best-suited for solar given how simply the solar modules can clip onto the seams. However, they are also the most-susceptible to being designed too close to building code lines and leaving little margin left to add weight. More complex, heavier structures like gravel-covered ballasted roofs can lead to a more involved mounting process, but the weight in gravel removed to place down the solar tends to be more than the solar itself, easing tension on the structure.

Don’t Make Heavy Weather about the Heavy Weather

Another common customer concern stems from adding load to roofs in areas that experience heavy snowfall. However, building codes are stronger in these areas, and most roofs can handle solar and snow without a problem. Developers also consider wind pressure, seismic force, and all other factors related to live load when assessing the roof, making sure all weather scenarios are considered. No matter the climate, solar energy systems must adhere to local codes and survive exceedingly well in extreme weather. Our engineering team has worked extensively in the Northeast, an area prone to various weather-related issues, and the team estimates over 75 percent of rooftops in the area are suitable to handle solar. As the Illinois rooftop solar program opens this summer, we expect similar rates of success in harsh Midwest winters.

Warranty Worries Are Not Always Warranted

Customers worried about their roof’s warranty can also rest assured. Any experienced developer should work with the original roof manufacturer to ensure that the warranty remains intact throughout the installation process. Solar arrays are designed to allow for maximal mobility for routine repairs that may be needed during the life of the system. Customers that go solar through a power purchase agreement (PPA) can often tailor the length of their PPA to align with the remainder of their roof warranty, something that has become more common as PPA agreements have become more flexible in length.

If your roof is deemed unsuitable for solar after analysis by a development team, which can occur for several reasons (age, condition of the membrane, etc.), a replacement is always an option. Roof replacements are costly, but in many cases align perfectly with the timing to go solar. The developer can work with the customer to design an optimal roof for the system, whose energy savings can help pay for the replacement over time. Customers will also be saving on the repairs the roof would need if not replaced, especially if the warranty has ended or is set to end.

It would be foolish to expect customers to put thousands of panels on their roof without bringing up questions and concerns involved in the process, and almost all of these questions have been answered countless times by developers. Our team has worked on roofs of all types in a variety of areas, and commercial customers looking to explore solar should reach out to our team at


Sol Systems, a national solar finance and development firm, delivers sophisticated, customized services for institutional, corporate, and municipal customers. Sol is employee-owned, and has been profitable since inception in 2008. Sol is backed by Sempra Energy, a $25+ billion energy company.

Over the last eight years, Sol Systems has delivered 700 MW of solar projects for Fortune 100 companies, municipalities, universities, churches, and small businesses. Sol now manages over $650 million in solar energy assets for utilities, banks, and Fortune 500 companies.

Inc. 5000 recognized Sol Systems in its annual list of the nation’s fastest-growing private companies for four consecutive years. For more information, please visit