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How Tree Shade Affects Solar Panels

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Sometimes we run into a client that has lots of trees around their house and they want to know how tree shade will affect their solar panels. Any shade on solar electric panels can be devastating, but by using microinverters we can limit the impact, and only panels that are shaded will be affected, leaving neighboring panels to work at optimum levels.

Tree shade is tricky, because the amount of shade cast depends on the density of the foliage, and trees tend to move (in the wind – they don’t usually walk around) and they grow over time. We can only approximate the impact that trees will have on solar panels. There are some shading analysis tools we can use, and solar installer experience can go a long way in providing a ballpark estimate of tree shade impact.

To illustrate the effect of solar panel shading, I took a photograph this morning of my solar electric system in Fort Myers, FL. Then I looked at my solar energy monitoring system through the Enphase Enlighten Manager. This is the professional version of the monitoring system that comes with every Enphase microinverter solar electric system we sell. We can monitor the output of each solar panel independently, providing a robust look at the impact trees have on systems.

Monitoring Tree Shade on Solar Panels

Below is a video to illustrate what happened between sunrise and about 4:00 pm today. Of course, this would look different every day of the year depending on the sun’s path and the weather, but it illustrates that shaded panels still produce power, just not as much as other panels until the sun moves and shade disappears.

As you will see in the video, the lower right (southwest) portion of my solar array is shaded by a palm tree. I knew this would cause shading, but I also knew I could use it to show my clients what happens. The results are pretty clear. In the early morning the panels in this corner produce little power relative to the others, and as the day goes on the shade dissipates and these panels start matching the others.

 

Unshaded Solar Panel Output

Note lifetime output of 920 kilowatt-hours.

Unshaded Solar Panel Output

Unshaded Solar Panel Output

Shaded Solar Panel Output

Note lifetime output of 625 kilowatt-hours.

Shaded Solar Panel Output

Shaded Solar Panel Output

Shading Analysis

You can look at the shaded panels compared to the unshaded panels for any timeframe. A quick look at the lifetime output of the panel at the very lower right compared to the panel in the top center shows that I have lost about 27% of the energy it could have produced relative to the whole system. That sounds like a lot, but not all shaded panels are affected to that same extent.

In all, the palm tree has caused me to lose about 2.4% of the system’s potential output over time. If you do the math on that, it would probably cost me more to have the tree removed than the energy I would gain from removing it.

So the question becomes, should you install solar panels where you know they will be shaded at times? That really depends. It is definitely not ideal, and your return on investment will still be lower, but if your goal is to produce the most energy possible over time and you are willing to sacrifice in terms of ROI, you may decide it’s worth it. That’s a personal decision that should be made with the guidance of a solar energy professional.

 

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