What's the most effective and safest way to clean solar panels?

March 14, 2018

How to clean solar panels


Soft washing solar panels is a great market. Think of the acres of panels that are popping up in farmer's fields all over the country, as well those on the roofs of houses, factories and offices.

All need professional cleaning.

Are solar panels self-cleaning?

Well, it is true that the majority of solar panels are promoted as being self-cleaning, and so should require relatively little additional cleaning.

However, "self-cleaning" is a bit of a misnomer, like "self-cleaning" windows. For sure they don't need cleaning so frequently, but they do need regular cleaning to remain efficient producers of electricity.

Quick tip: Grime, bird poo and heavy dust don't need to cover an entire solar panel to have a negative effect on it's performance.

In certain situations, such as solar panels mounted in a particularly dry area (allowing dust and bird droppings to build up), or where the solar panel's tilt angle is less than five degrees, most manufacturers recommend regular cleaning to ensure the panels continue to work efficient as electricity generators.

What type of water should you use to clean solar panels?

Solar  panel manufacturers suggest that using water devoid of detergents – ideally de-ionised – will be sufficient for cleaning most solar panels, most of the time.

Manufacturers strongly recommend not using detergents that can cause streaking and thus compromise the effectiveness of the panels. 

Quick tip: Window Cleanze does not leave streaks and so is suitable for cleaning solar panels. Just add a few drops of Benz Window Cleanze to your de-ionised water.

A window cleaning WFP (water-fed pole) set-up using de-ionised water is the best way to clean solar panels. And adding a few drops of Window Cleanze to your de-ionised water will help to quickly remove bird droppings and spider poo. 

What is "pure" water? This is a generic term used to describe de-ionised water and distilled water. Both could be called "pure" but are produced through different processes.

Distilled water is usually produced in large industrial settings, while de-ionised water is the water produced on a daily basis by us and by the vast majority of water-fed pole (WFP) window cleaners.

Can you use tap water to clean solar panels? We do not recommend using ordinary tap water because it is mostly anything but pure. It can leave deposits and smears on the solar panels that will reduce their efficiency.

Soft water will not cause as much of a problem, although we do not recommend using even that, and advise against using hard water whenever possible.

Quick tip: In hard water areas* it is crucial to wipe all such water, if used, from the solar panels before they dry, to prevent limescale/calcium building up.

* Ideally, don't use hard water on solar panels at all.

Can a roof be cleaned underneath a solar panel?

Solar panels should have the area beneath them cleaned and treated with Bio Cleanze – ideally at a strong dilution of 20:1 to ensure the longest possible residual protection from re-colonisation – before they are installed.

Attempting to treat the moss and algae under installed panels is fraught with danger. There's the wiring to consider. And the effect of water and a biocide on the underneath of the panel.

We suggest contacting the manufacturers of any given panel and asking them for advice. And, the safest option, if you are at all unsure as to whether you have the necessary skills and experience, sub-contract the job to a specialist solar panel cleaning company.

How to soft wash a roof that has solar panels

When soft washing the roof with Benz Bio Cleanze or Benz Lightning Cleanze it will be important to ensure the solar panels are not splashed or covered with spray drift. It is highly unlikely they would be damaged but it's best to be too safe now than very sorry later.
The solution is simple: Use a brush for applying the biocides to a roof, which will enable you to easily avoid getting biocide onto the solar panels. And of course immediately cleaning the solar panels after soft washing a roof with de-ionised water and Window Cleanze will remove any biocide that may have accidentally got onto them.

Contact the manufacturers of the solar panels

If you are in any doubt about the best way to clean solar panels we suggest contacting the manufacturers of the panels and asking for their advice.

Materials are continually evolving and it would be wise to check that they have not introduced some new substance into the construction of the panels that cleaning could inadvertently compromise.

Quick tip: Get hold of the manufacturer's Product Data Sheets (PDS) and Safety Data Sheets (SDS), which should suggest recommended ways to clean their products.

Is there a danger of electrocution when cleaning solar panels?

The fact is that solar panels are electricity generating machines and should be treated with the same care and respect due to all electrical equipment. Even a small current passing through the heart can be fatal.

If a contractor does not have a good working knowledge of how to safely clean electrical equipment, we suggest sub-contracting the work to a specialist, or getting trained in the required skills and H&S procedures.

How to clean solar panels contaminated with algae?

Benz Bio Cleanze diluted 30-50:1 is a good choice (after checking with the manufacturer of the solar panels that the product will be safe to use).

Simply spray the panel, let Bio Cleanze activate for 30-60 minutes, then agitate with a solar panel WFP brush and de-ionised water (treated with Window Cleanze) to clean the panel.
Use the correct brush: A normal water fed pole window cleaning brush should not be used on solar panels but rather a special soft brush designed for cleaning solar panels.  We use a "flocked" soft brush, which Gardiners recommended in their solar section.

Do not use scrapers on solar panels. Gentleness is the key to safely cleaning solar panels.
As always, with your customer's permission, treat a small test area of one of the panels, then get your customer's agreement that the result is to their satisfaction and obtain their permission to treat all the panels.

We hope this information is helpful and sincerely wish you great success in your soft washing business,

Ben, Leo, Fiona, Stevie & Anthony

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how to" – into our in-site Search Engine (magnifying glass icon on the main menu).

Click here to download our Product Documentation Pack (includes Application & Dilution guides, SDS, PDS, RAMS, PPE & Mask info, COSSH, sample Contract and more)

Order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 

Online: www.benzsoftwash.co.uk

Ireland and other countries

Phone: 00353 214 622 978

Online: www.benzsoftwash.com

Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

PS: Click here to set up your "Clean & Maintain" programme
. After completing an initial soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for you and your customers.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

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