How Tree Shade Affects Solar Panels

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.

If you are looking into shading impacts on solar pool heaters, go here.

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.

 

  • Comment (2)
  • Nick Renold says:
    Your comment is awaiting moderation. This is a preview; your comment will be visible after it has been approved.
    That’s not correct actually. Regardless of the brand of modules, a modern panel with bypass diodes won’t affect the other full sun panels very much, even on a string inverter. (Parallel strings on one MPPT is a more complicated discussion, which I will not go into.) The worst case impact of a shaded module in a series string is the loss of that module’s output, and a few watts of power consumed when the rest of the string drives its current through the bypass diodes of that shaded panel (about 30 watts assuming 3 diodes and 16 amps running on the string).
  • The Torrance Electrician says:
    Your comment is awaiting moderation. This is a preview; your comment will be visible after it has been approved.
    Great article! Tree shade can significantly affect the output of solar panels by reducing the amount of sunlight they receive. Even a small amount of shading can cause a disproportionate reduction in the efficiency of the entire system. It’s important to ensure that your solar panels are installed in a location that receives maximum sunlight throughout the day, and that there are no obstructions like trees, buildings, or other objects that could cast shade on them. If shading is unavoidable, technologies such as micro-inverters, optimizers, or bypass diodes can help mitigate the impact of shading. Proper planning and design of the solar panel installation can help ensure maximum efficiency and energy production.
  • Jim Brown says:

    A very helpful solar / shade calculation. Though not stated, I assume your example was based on solar panels that use individual micro inverters attached to each panel. What would the results have shown if Tesla solar panels were used since they are deploying string inverters and not separate micro inverters.

    If Tesla panels were installed, would not multiple adjacent full sun panels be affected if they are connected to the panel(s) in the shade?

  • David Campbell says:
    Your comment is awaiting moderation. This is a preview; your comment will be visible after it has been approved.
    The article would guide you on how to design a solar PV system by considering your home’s energy requirements. It would provide an overview of the following topics: – System components – Mounting Systems – Design steps – Site evaluation – PV Module Sizing – Inverter and Battery Sizing

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