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How to Clean Solar Panels | An Expert Guide

Rooftop solar panels have changed the game for homeowners looking to power their homes with clean, affordable energy. But to make the most of the investment and keep your solar panels in top working order regular maintenance is essential. After all, solar panels take a beating in the elements day in and day-out.

In this guide on how to clean solar panels, we cover everything you need to know about cleaning solar panels, from the best techniques (and what to avoid) to when you need to call in a professional.

Why is cleaning solar panels important?

To understand why cleaning solar panels is so important, it’s helpful to understand how they work. Put simply, solar panels house photovoltaic (PV) cells, which produce electricity when they’re exposed to sunlight. To protect them from the elements, but still allow light to filter through, these PV cells are covered by a clear glass casing.

Over time, this glass casing gets dirty. It accumulates dust, bird droppings and dirt that won’t simply wash off in the rain. Over time, this layer of grime reduces the amount of sunlight that reaches the PV cells, reducing the solar panels’ output. According to the National Renewable Energy Laboratory, solar panel ‘soiling’ as it’s called, can reduce solar output by as much as 50 per cent in some countries.

How to clean solar panels – five simple steps

Now you know why cleaning solar panels is important, here’s how to clean solar panels in five simple steps. And spoiler alert – you don’t need any special equipment!

1. Assemble your equipment

To clean your solar panels you will need:

a ladder to gain access to the solar panels
a bucket full of a gentle cleaning solution, such as dishwashing detergent. If you’d prefer, you can also purchase a specialised solar panel cleaning product.
a soft cloth (such as a sponge, rag, or Chux) or squeegee to apply the cleaning solution. A long handled soft broom can also be handy for solar panels that are hard to reach.
a soft-bristled brush to help remove more stubborn spots, like bird droppings
clean water to rinse the panel
a soft, clean cloth for drying the panels.

2. Rinse the panels

Before applying any cleaning solution it’s a good idea to rinse the panels to remove any loose dust from the surface. This will also help to soften up any more stubborn pieces. If your garden hose reaches the panels, you can try using it on a gentle setting, otherwise simply pouring water from a bucket onto the panel will do the trick. The trick is to be gentle with solar panels, so avoid the temptation to use a pressure washer.

3. Apply the cleaning solution

Once the panels are damp, apply your cleaning solution with a soft cloth or squeegee, and wipe the panels. If you have stubborn debris it can be a good idea to leave the solution to work its magic for a few minutes, but do note that cleaning solution can dry out quickly on solar panels. If you’re still having trouble removing tough spots, it’s ok to use a soft-bristled brush to scrub at them, but avoid using anything abrasive like metal scourers or wire brushes that could damage the panels.

If your solar panels are out of reach, a soft broom can help you with this step. That said, you should always be as close to the panels as you can be and should avoid reaching unsafely as it can increase your risk of falling.

4. Rinse and repeat

Once you’ve finished wiping the panels, rinse them with clean water to remove the cleaning solution and grime. Depending on how long it’s been since you cleaned them, you may need to apply some more cleaning solution to remove any remaining dirt.

5. Dry the panels

Use a soft cloth to gently wipe the panels dry and remove any cleaning residue. A car chamois works really well for this if you’ve got one. While it can tempting to leave the panels to dry out in the sun, it’s better to wipe them dry to avoid any residue being left on the panels which might impair their function.

Safety considerations when cleaning solar panels

If you choose to clean your panels yourself, it’s essential to consider your personal safety. Specifically:

Hire a professional solar panel cleaner if you’re not confident on the roof, or if your solar panels are in a hard-to-reach place.
Always ensure the ladder you use to access the roof is in good condition, and placed on stable ground. For extra security, have someone hold the ladder while you’re on it.
Wear appropriate footwear. It’s easy to slip on roofs—particularly if they’re sloped, or they get wet from the cleaning solution.
Clean solar panels on a cool day. Metal roofs get hot in the sun, and you don’t want to get sunburnt or dehydrated.
Wear a hardhat or helmet just in case. 9/10 times you probably won’t need it, but it’s much better to be on the safe side.

How to clean solar panels – what to avoid

When it comes to how to clean solar panels, the motto of ‘gently does it’ is the ticket. Treat them like you would windows. With that in mind, here are some things to avoid when cleaning solar panels:

Don’t step on the panels, or apply too much pressure. Solar panels aren’t designed to be walked on, and may break under this type of force, voiding their warranty and reducing their efficiency. Similarly, avoid using pressure washers or other high pressure hoses as the force can cause damage to the solar panel seals, which in turn can reduce their efficiency or allow water to seep into the panel, potentially damaging the electrical components.
Avoid using abrasive cleaning products. Metal sponges, hard-bristle brushes or cleaning products with abrasive material in them (like Gumption) can scratch the glass on the solar panel, reducing the amount of light that gets into the PV cells. While it can be tempting to use these to speed up the process—particularly if your panels have a lot of tough residue on them—patience is the key. It’s also best to avoid harsh cleaning products that can similarly damage the panels.
Clean the panels on a cool, overcast day. Not only will this make for a more pleasant experience for you, but it will make cleaning the panels a lot easier, because the water you’re using won’t evaporate as quickly.

How often do you need to clean solar panels?

Just like it’s a good idea to clean your gutters twice a year, most experts recommend cleaning your solar panels roughly twice a year. Semi-regular cleaning is important to keep the surface of the solar panels free of dust and grime that can reduce the amount of sunlight that makes it to the PV cells.

But as with all roof maintenance, this is a rough guide, and you should keep in mind your location when considering how often to clean your solar panels. For example, if you live in an outback area of Australia where there’s more dust, you might need to clean your panels more frequently than twice a year. By comparison, if you live in an alpine or coastal region where you get more frequent snow or rain that helps to wash away dirt before it can accumulate, you might only need to clean them once a year.

The proximity of your solar panels to trees on your property will also influence how dirty they get. If you have trees around your house, chances are your panels will accumulate more bird droppings. Depending on the type of tree you have, they may also be more exposed to tree sap, or deciduous leaves that can leave marks on your solar panels over time.

How do you know when to clean solar panels?

Generally speaking, time is your best guide to when your solar panels are due for a clean. If it’s been longer than six months, it’s a good idea to clean them—or book in a professional solar panel cleaner. In some cases though, particularly if you’ve never cleaned your solar panels, system performance might give you an indication that it’s time to clean the panels. As we mentioned above, dirt and dust accumulation can reduce the efficiency of your system by up to 50 per cent, so if you’ve been observing a steady decline in power output, it’s a good idea to inspect your panels.

When should you call in an expert?

While it’s possible to clean solar panels yourself, it’s often a good idea to call in an expert. Cleaning solar panels isn’t difficult, but it can be unsafe. Often, solar panels are mounted on sloped sections of the roof, and may be quite high up making them challenging to reach from a safe position. The risk of slipping on a metal roof is also increased because of the water you’ll be splashing around to clean the panels.

Specifically, it’s a good idea to call an expert if:

Your solar panels aren’t easily or safely accessible.
Your solar panels are extremely dirty and you want a professional clean.
You aren’t comfortable working at heights, or have limited experience being on a roof.

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