How Does Shade Affect Solar Panels?

Welcome to number 4 in our technical blog series. This time we did some testing to answer this question: how does shade affect solar panels?

If you’ve been following along, you know that one of the things that makes us very different as a solar company is the testing we do. We want to make sure we are providing the best quality hardware and beautifully installed systems. If something is going to be on your roof for the next 30 years – or more – we want it to look amazing and perform as it should. Solar is a big investment, so it’s important to know you’re getting a system that is built to last. Not only that, but the kinds of testing we do helps us to continuously increase our solar expertise.

If you haven’t read our previous entries on microinverter output, solar panel performance, and our solar racking test – you might find those interesting as well!

A bit about shading and solar

Shading is a problem for solar panels since having just one cell shaded in the module can significantly reduce the power output.

Filtered light, like on cloudy days or through empty tree branches (depending on density) in winter, is still enough power for solar panels to generate anywhere from 20-60% of capacity. Hard shading, produced by chimneys, dormers, or objects placed over the solar panels that block the sunlight entirely, can completely crash the power output of the panel while the shading is occurring.

Although microinverters and optimizers have significantly improved shadings issues caused by traditional string inverters, where shading one cell reduces the output of the whole string of panels (or possibly the entire system), it is good practice for a solar provider to consider shading impacts right from the initial design stage, aiming to maximize each solar panel that is installed.

The Test: How does shade affect solar panel output?

In order to have a better understanding of the shading effects on solar panels​,​ we performed our own shading test to measure the real impact of hard shading on the solar panels by reproducing different shading patterns over the 325W LG Neon2 solar panels on our test site:

Shading Test - How does shade affect solar panels?
Shading Test – Solar Panels

Here are the results from solar panel #1. With one cell shaded, power dropped by 80% :

Output results from panel #1
Output results from panel #1

For panel #2 with three cells shaded, solar power dropped by 97.7%:

Output results from panel #2

Output results from panel #2

And for panel 3, with only half a cell shaded, power dropped by 50%:

Output results from panel #3

Output results from panel #3

As you can see, hard shading can have quite an impact on solar production. This is why at SKYLIT we design each system to address potential shading issues, when it is possible to do so. It is not always necessary to entirely avoid adding panels where hard shading can occur; as the sun moves across the sky, often the affected output is for a short period of time so the benefit is worth it. But shading, and its affect on power output, is something to keep in mind when looking at going solar.

Amanda Brulé

Amanda is VP Sales & Residential Projects at SKYLIT.