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How Will Solar Panel Shading Affect Your Home Solar Plans?

I’m about to tell you something that you probably didn’t think you would ever hear from a solar contractor…your home or business may not be a good fit for solar. That’s right, I said it!

Yes, solar electric systems can reduce or eliminate your electric bill, but not every location works for solar. While there are a number of factors that determine if your home is solar-worthy, I find that solar panel shading seems to be the number one topic that comes up during site evaluations. Living here in the Garden State, New Jersey homeowners often have lots of beautiful trees on site, but those trees may cast a shadow on your dreams of going solar.

Solar panels produce energy by harvesting the sunlight that falls on them, so they are very sensitive to shading and can lose efficiency when shaded by trees, chimneys, or even vent pipes.

Potential rooftop solar panel shading issuesWhy does solar panel shading matter? PV modules are made up of many cells, and in the wiring design of many solar panels, the individual solar cells are connected in series (called “strings”, like Christmas lights) and if any portion of the panel is shaded then the entire output of that panel is affected. So shading from a tree branch, even if it obstructs a small area, can reduce your solar panels’ production during the part of the day that the branch shades the panels. This is true even if there are no leaves on the branch.

Shading keeps your solar power system from generating electricity. In addition to reducing the money you will save on your electric bill, the reduced production may also mean a decrease in the financing available to have a solar system installed. SunRun, one of our solar financing partners, requires a minimum level of production to be eligible for their programs. Shading can seriously affect the viability of your solar power project.

Utility electricity meterIn order to cash in on $0 down solar, your home or business would need to meet shading standards, which take into consideration orientation and pitch. It is customary to point the solar panels in a direction that would allow them to capture the most sunlight possible. In our service area a roof that faces south is best, while southeast- or southwest-facing roof space may work as well. As the orientation moves closer to east or west there is an inverse relationship between the orientation (azimuth) and the pitch of the roof. If your roof is facing east or west then the pitch would have to be slow in order for us to be able to design a workable system. While the ideal pitch at our location is 35 degrees, we can design systems that work well on pitches that range from 5 to 60 degrees.

The SunEye can detect potential solar panel shading issuesSo how can you tell if your site will work? We can tell you! We offer free site evaluations that include measurements of all of the variables. The Real Goods Solar (formerly Alteris Renewables) in-house solar contractors use cutting-edge technology to measure the amount of sunlight that falls on your roof over the course of the year. We then advise our customers of any potential challenges and make recommendations to improve the solar system’s performance. The most important thing is that we communicate our findings so there won’t be any surprises.

For example, on a recent site visit in Passaic County, NJ, we found a major shading challenge because the customer’s home was in a heavily wooded area. Initially, it did not look like a good fit for solar; however, the homeowner was passionate about going solar and he committed to taking down a number of trees to make the project viable. The customer is comfortable with harvesting some firewood in order to contract a solar power system that will provide the equivalent carbon footprint offset of planting 80 acres of trees.

Some objects that create shading are not easily moved, such as chimneys or a neighbor’s tree. Obstactles of this nature can be deal-breakers, but we will assess each project and provide detailed feedback on all your options.

In conclusion, shading from trees, obstructions, orientation and pitch play a critical role in determining whether a solar power system will be a good fit for your location.

1 Comment
  1. Thanks for this, well written and great view point

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