Solar Panel Cleaning: Best Practices and Simple Guide

By Hannah Glenn
18 June 2018
What is the best way to clean solar panels?

Dirty panels? There are some instances where solar panels might need cleaning, but most of the evidence says solar panels are self-sufficient and low-maintenance. We'll get to the best way to clean your solar panels in a minute. But first, let's look at when and why you might need to invest in solar panel cleaning equipment or hire a professional cleaning service.

Google did a study on the need to clean solar panels. They found that tilted panels don’t require cleaning as much as flat panels. This was confirmed by another study by engineers at the University of California, San Diego, which found that a minimum five-degree angle helped debris to slide off the panels.

The UCSD study also found that normal debris such as dust, dirt, and pollen have a minimal effect on efficiency. Less than 0.05 percent efficiency is lost on average. For a homeowner, that adds up to saving about $20 a year by cleaning their solar panels halfway through the summer.

Essentially, under normal circumstances you’ll likely pay more to have your panels cleaned than you’ll earn back in solar efficiency.

When you might need to clean solar panels

Some exceptions might be if you notice excessive bird droppings, after heavy dust storms in places like Arizona or when you live directly next to or downwind from major highways, factories or agricultural fields. In these instances, it's possible to generate enough grime to call for cleaning.

Leaves in the fall and heavy snow in the winter can also require action, but you can easily remove these with a long roof rake like this.

Most snow will melt fairly quickly as the dark solar panels attract heat and sunlight. And snow actually cleans your panels as it melts, taking any dust and dirt with it as it slides off the slick module surface. Read more about solar and snow here.

Some of the sunniest places also don’t get much rain, which does a good job cleaning panels. If you can see a thick film accumulated on your panels or notice significant a dip in efficiency, it might be time for a wash.

How to clean those dusty, dirty solar panels

1. Be sure to check your panel manufacturer instructions for shutting down the system before cleaning, if necessary. Try not to go on the roof to clean your system. It’s risky both for you and your panels.

2. Brushing any loose dirt off before spraying them with water will make the squeegeeing process quicker and easier.

3. A good nozzle attachment on your garden hose might work just fine. If a lot of dust and dirt has accumulated, you might need to clean more thoroughly. Try to clean with squeegee extension like this one. If you’re interested in the whole kit and kaboodle for home solar cleaning equipment, Mr. LongArm is one of the most popular.

4. Don’t use metal objects, abrasive products or detergents. Scratches on a solar panel can create shadows and affect efficiency. Simply use clean water and a cloth-covered sponge or soft plastic brush.

5. Rainwater is low in mineral content, but some people have “hard water” or mineral-rich water from the tap. If this is the case for you, just be sure to squeegee the panels dry to avoid mineral deposits and streaking.

When and How Often to Clean Your Solar Panels

Early morning or in the evening (ideally on an overcast day) is best. Too much sun on wet panels can cause them to dry too quickly and smudge.

Note: If you can’t clean your panels from the ground, hire a company. They have the appropriate safety equipment for navigating the roof.

But remember...

Generally, cleaning your solar panels isn’t something you need to bother with. The best way to figure out if your panels need cleaning is to assess the above conditions. For the most part, solar panels are self-cleaning.

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