Solar Panel Cleaning: Maintaining Solar Panels

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If your solar panels aren't kept clean, the amount of electricity they'll be able to generate can fall by as much as 30%.

Your solar panels will need cleaning once or twice a year, when they look visibly dirty or when your electricity generation starts to fall.

You can buy a solar panel cleaning kit and clean your solar panels yourself, or hire a specialist solar panel cleaning company to do it for you.

One of the many advantages of solar panels is their reliability. Their power source – sunlight – is available every day. As long as your panels are good quality and have been properly installed, there should be nothing to stop them working well for decades.

To work at their maximum efficiency, however, solar panels need to be kept clean. If you experience a decline in the amount of electricity your solar panels are producing, it’s probably due to a build-up of dirt and debris on their surface, such as dust, plant sap, lichen and bird droppings.

This guide to solar panel cleaning will give you advice on what you need to do, how often you need to do it and how to ensure it involves as little effort as possible.

solar panel cleaning

Why You Should Clean Solar Panels

Solar panels use the sun’s energy to create electricity. They will work whenever the sun is out, but the sunlight needs to be able to reach the photovoltaic cells inside the panels. This is why you should not install solar panels in the shade - anything which blocks light from getting to part (or all) of the photovoltaic cells will massively reduce a solar panel’s efficiency (and how much electricity it can generate).

Because solar panels are installed on your home’s roof, they will get covered over time in debris like dust, sap, leaves, soot and yes, bird droppings. These will all obstruct the sunlight from reaching the photovoltaic cells inside the panels, and could have a big effect on their output.

With some types of solar panel, even a tiny obstruction can cause a large drop in electricity production, as the few cells that are in shadow can hugely drain the power that the rest of the cells are producing.

So, if you don’t keep your solar panels clean, they could end up generating a lot less electricity than they’re capable of. Plus, if your solar panels are registered with the Government Feed-in Tariff, this means you’ll end up receiving less money from the electricity you generate and sell back to the National Grid.

In fact, it’s been estimated that not cleaning your solar panels can reduce their performance by as much as 10% to 30%. This translates into a loss of around £40 to £110 annually from the Feed-in Tariff, for a home which has installed a 4kW solar system.

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Solar Panel Cleaning: When to Do It

The obvious answer is when they look dirty. But how often is that likely to be? Manufacturers often recommend cleaning your solar panels once or twice a year, but your installer should be able to give you guidance when they fit your panels. However, if you do notice that your solar panels have become less efficient, this might be a sign that they need a good clean.

If you live near a busy road or on a farm, you’re likely to need to clean your panels more regularly than if you live somewhere where there’s less pollution or dirt. The same may be true if you live by the coast, as salt from the sea can build-up on the surface of your panels.

Although the UK gets a lot of rain, we don’t recommend relying on it to keep your solar panels clean. You will need to invest some time and elbow grease into cleaning your panels, but make sure not to overdo it. After all, you don’t want to cause any unnecessary damage to your solar panels, so only clean them when they really need it.

How to Know When Your Solar Panels Have Become Less Efficient

Make sure to keep track of how much electricity your panels are generating. If you keep a record of the figures on your generation meter each week, you can see if power generation has dropped beyond what would be attributable to variations in the weather. You can get apps and monitors to help you keep track of your system’s performance. You should also compare your output with your manufacturer’s estimate of how much electricity your system should generate. Even if you don’t think your panels need cleaning, these measures are important aspects of maintaining your solar panels.

To find out more about how much electricity solar panels generate, visit our guide on solar panel output.

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How to Clean Solar Panels

Given the amount of money you will have spent on your solar panels, the last thing you want to do is damage them by cleaning them incorrectly.

You can buy special solar panel cleaning kits that are designed to help you clean them safely and effectively. A typical solar panel cleaning kit will contain a non-scratch brush, a long or telescopic pole, and a squeegee, sponge or cloth. It may also contain equipment to purify your mains water so you don’t have to worry about leaving any mineral deposits on your panels’ surface when you clean them.

Here are our tips to help you scrub up your solar panels and leave them looking sparkling clean:

  1. Turn them off before you start cleaning. Don't get electrocuted. Make sure you turn the whole system off – but remember that the cables will still be live. Damaged or exposed cables must be repaired by an electrician before you do any cleaning.

  2. If you can, clean them from the ground. Don’t, whatever you do, climb onto the roof unless you have the appropriate safety equipment and training. If you are using a ladder, make sure it’s secure – get someone to hold it.

  3. Use a soft brush. Or a squeegee with a plastic blade on one side and a cloth-covered sponge on the other. Attach it to a long pole and a hose with a nozzle so you can aim the water properly. If the panels are dry, brush off any loose dirt before you get them wet. Use a lint-free cloth to dry the panels.

  4. Warm soapy water is all you need. Don’t use metal objects or abrasive products, or scrub excessively hard, or you might scratch and damage your panels. You may need isopropyl alcohol to get rid of oily stains.

  5. If you are in a hard water area, use rainwater or distilled water to rinse the panels. Or if you do use hard water, make sure you dry them well as the minerals in hard water can form deposits on the glass as it dries.

  6. Clean your panels when it’s not too hot and sunny. So early in the morning, in the evening, or on an overcast day is ideal. If it’s very sunny, the water will evaporate more quickly and might leave smears; cold water on very hot panels might also damage the glass. Early morning can be a particularly good time as dew may have settled on the panels overnight and softened the dirt.

  7. Check your warranty to find out what it says about how you should clean your solar panels to make sure you don’t do anything that invalidates it – for example, your manufacturer may say you should not use pressure washers or chemical cleaners.

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Professional Solar Panel Cleaners

You can also hire professional solar panel cleaners to clean your solar panels, as again, they will know how to do it safely and effectively. This will be more expensive, but might be a good option if your panels are difficult for you to get to.

Your installer is the best person to ask for a cleaning company recommendation and an estimate of how much it should cost. Ask to see their certificate of insurance, in case they have an accident while working on your home, and also their certificate of training. If they are going to be working on an elevated platform, they should have a PAL card issued by the IPAF.

Professional solar panel cleaners may include other checks and maintenance as part of their service, like checking for damage to the glass and frames.

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