Ideally, you need to totally avoid shading for solar panels to produce electricity optimally. However, solar panels can still work in the shade, but with reduced efficiency.

You should pay attention to shading if you have a solar power system and want it to function optimally at every time of the day, all year long.

In this post, we’ll discuss how shading affects solar panels. Specifically, we’ll answer questions like:

  • Do solar panels work in partial or full shade?
  • How efficient are solar panels in the shade?
  • How can solar panels charge in the shade?
  • Are there shade-tolerant solar panels?
  • How can you reduce shading on your solar panels?

Let’s get started.

Do solar panels work in partial or full shade?

If a solar panel is fully shaded, the power output may drop to zero. Partial shading also causes power output to drop drastically. Partial shading of even one cell in a 36-cells solar panel will reduce the power output of the entire system by the same amount as the percentage of the area shaded.

You’ll understand how shade affects solar panels if you understand how solar panels work.

Certain components in solar panels’ cells capture sunlight to generate electricity. Thus, anything that reduces the amount of sunlight reaching the solar panels’ cells will affect the panels’ power output.

When a neighbouring tree or structure casts a shadow on your solar panels, the shaded part does not receive sunlight. Not only does the power efficiency of the shaded part drop, but it forces the efficiency of the whole system to drop.

How efficient are solar panels in the shade?

A shaded cell in a solar panel will make other cells function at their reduced power output. Also, a shaded panel will reduce current flow in other panels in the system.

How partial shading of even one cell affects the whole panel

Solar panels’ cells are usually connected in series. As a result, a solar panel can only work at the power of its weakest link. If one cell is partially shaded, its power output reduces, reducing the power output of the other cells.

Thus, it does not matter whether other panel parts receive good sunlight. Every cell reduces its power output to that of the panel’s weakest link.

So, in a 36-cell solar panel, if just a half-part of just one cell is shaded, the efficiency of the shaded cell, as well as every other unshaded cell, will drop by 50%.

How shading of one panel affects the whole system

Just as it is with solar cells on a panel, so it is with solar panels in a circuit. If the output of one solar panel drops because of shading, all panels in the circuit will suffer a corresponding drop in power output.

A study has shown that power generation reduces to zero if a solar panel is shaded by up to 75% or more

The collection of solar panels is divided into strings, and a solar PV system may consist of one or more strings.

Power flowing through a string of solar panels can be thought of like water flowing through a pipe. The flow rate through the pipe is constant when the pipe is free, but if there’s a clog in a part of the pipe, water flow through the pipe is reduced.

Similarly, if something casts a shadow on one of the panels in the string, the current flowing through the entire string reduces.

How can solar panels charge in the shade?

Various technologies make solar panels function in the shade. These include MPP Tracking technology, bypass diodes, microinverters, and DC optimisers.

MPP Tracking. Maximum Power Point Tracking is a technology that ensures that inverters receive maximum power from solar panels. The trackers check the voltage from the panels and adjust it to always be at the inverter’s preferred input range. 

So, if panels’ shading causes reduced power output, MPPT can help the string inverter negate the shading effect.

By-pass diodes. These are devices within modules that allow current to bypass shaded panels’ cells.

Ordinarily, the output of the unshaded cells is brought down to that of the panel’s weakest link (the shaded cell). But with by-pass diodes, the higher current of the unshaded cells flows through the string by-passing the shaded cells.

Microinverters. A system with microinverters has an inverter installed for every solar panel. Each inverter is equipped with MPPT, which adjusts voltage, so the inverter functions at its maximum powerpoint. 

Microinverters allow each panel to function independently. With the set-up, reduced power output in a panel because of shading will not affect the power output of other panels. Microinverters typically reduce the effect of shading by 3 – 12%.

DC Optimisers. Instead of microinverters, you can add DC optimisers to each panel to make them work optimally without affecting other panels.

A DC optimiser in a shaded panel will boost the power at its output to match the power from the unshaded panels.

Are there shade-tolerant solar panels?

Solar panels that use various technologies to increase performance under shaded conditions are shade-tolerant.

These include panels with micro-inverters, panels with DC optimisers, and panels with by-pass diodes.

Where does solar panel shade come from?

Solar panel shade comes from several sources, including natural and artificial obstacles.

Natural obstacles that shade solar panels

These are natural features around your house or overhead that can block sunlight from reaching your solar panels.

They include hills, trees, and clouds.

Hills. An elevated horizon from neighbouring hills and mountains can cast shadows on solar arrays, resulting in horizon shading.

Trees. These are the most common natural obstacles that shade solar arrays. The branching and foliage from nearby trees can cast shadows on panels. Your solar panels will last 25 – 30 years, which is enough time for trees around to grow.

Clouds. Clouds passing through the sky can cast a shadow on your panels to reduce their efficiency.

While there’s nothing you can do about this, you can take solace in the fact that shading from clouds is usually brief. Usually, clouds quickly pass over to allow interrupted flow of sunlight to your solar array.

What about very cloudy days when the clouds seemingly hug the sky and refuse to pass over quickly? 

Even in those days, your solar panels will still work because even such clouds still let some sunlight through. However, because sunlight hitting the array will be reduced, their power output will reduce.

Artificial obstacles that shade solar panels

These are constructions around your house that can cast a shadow on your rooftop panels. They include neighbouring buildings, other structures, your roof, and other panels.

Neighbouring buildings. The buildings of your neighbours can shade your panels, especially if they are higher than yours.

Neighbouring structures. Any other high structure, whether in your compound or the neighbours’ or the street can cast a shadow on your panels. These include elevated water tanks, electric poles, street lights, etc.

The roof. A part of a roof and roof structures like chimneys can cast a shadow on other parts of the roof. So, solar panels can be shaded by the roof they are on.

Other panels. Some solar set-ups have both higher and lower panels. Thus, situations can occur where higher panels cast shadows on lower ones.

Ways you can reduce shading on your solar panels

There are different ways to reduce shading on solar panels. These include using professional installers and investing in shade-tolerant systems.

Professional installers. The location and set-up of a solar array can affect how much shading it suffers.

In deciding on where on the roof and how to set up the panels, professional solar installers like Nectr use different mapping tools to look at the effect of shading. They’ll consider the terrain as well as surrounding structures. They’ll look at how these interact with the rooftop at every time of the day in the year.

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Shade-tolerant solar panels. Sometimes, eliminating shading may not be possible. At such times, you should reduce the effect of shading by using shade-tolerant panels.

Though different technologies are employed in shade-tolerant panels, the goal is to prevent reduced power output from a shaded panel from affecting the whole system.

You can go for systems with micro-inverters or DC optimisers. However, you will require relatively more investment because these systems are expensive than the regular solar PV systems.

Wrapping Up

Solar panels can work in the shade. Shading can come from natural obstacles like hills, trees, or clouds and artificial obstacles like neighbouring structures.

However, because solar panels use sunlight, their power output is reduced when shaded. Even if only a small part of a panel is shaded, the reduction in power output can be substantial. This is because, traditionally, solar panels function according to the power output of their weakest link.

Thankfully, you can reduce shading. One way is by engaging a professional solar installer like Nectr.

Using our vast experience and a range of tools and techniques, we’ll determine the optimal spot and solar setup that reduces panels’ shading. To reduce the effect of shading, you can also invest in shade-tolerant panels like those that use micro-inverters and DC optimisers.

Next Steps…

Interested in solar? Use our solar calculator below to know how much you’ll save with solar, find out what rebates you’re eligible for, and determine the positive impact your solar system will have on the environment.

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