Cleaning Solar Panels

How to Clean Solar Panels with Bio-Shield®

Including cleaning of:

  • Solar Photovoltaic Panels
  • Solar Hot Water Panels
  • Solar Pool Heating

Should I water blast clean or use Bio-Shield® to clean a Solar Panels?

Any lichen growth on Solar panels will completely block sunlight from reaching the photovoltaic cells reducing power output, efficiency and extending payback time. Left untreated lichen will eventually cover the entire panel.

Water blasting Solar Panels to remove, moss, algae and lichen may damage the panels with the high pressures required to remove lichens.
Water blast cleaning is a time consuming, expensive, and ultimately futile way to clean solar panels: if they are not sterilised in conjunction with water blasting, the lichen residue and spores on the surface will quickly regrow and block sunlight again. 

The best method for cleaning and maintaining Solar Panel arrays are exterior cleaning solutions like Bio-Shield®.

A simple application of Bio-Shield will kill and remove the growths and keep the surface clean and the panels functioning at peak efficiency for extended periods. 
Regular applications of Bio-Shield at the first sign of re-growths, typically every 2 to 3 years will effect a rapid clean up and keep the panels clean again for an extended period.

Why choose Bio-Shield® for Solar Panel Cleaning?

Bio-Shield® has been developed through 40 years of use in a demanding commercial environment, including extensive use on solar panels, so it works extremely well.

Bio-Shield® is a high quality product, and contains no bleach, salts, acids or phosphates and is safe to use on all types of Solar Panel

The high concentration of active ingredients in Bio-Shield® when compared to other outdoor cleaners such as Wet and Forget and 30 Seconds means it will cost less per diluted litre to cover more area at  lower cost.

Lichen on Solar Panel.jpg__PID:d42ea5fd-77a5-4a58-922d-92d69b88b5ef
Lichen on Solar Panel with Bio-Shield Applied.
Solar Panel Cleaned with Bio-Shield.jpg__PID:9f4b6363-a8b8-493e-bfbf-7472fdec4842

Bio-Shield® Application Instructions


Most falls from roofs are by homeowners working on their own roofs on the weekend. Dirty color coated roofs are slippery when wet so extreme care needs to be taken to prevent a fall.
The support frame on most solar arrays  can be used as a temporary anchor point to attach a safety rope .

Check out the Jet-Stream Applicator - you may be able  to spray the panels on an average sized roof from a ladder. If you have any doubts about your ability to to carry out this work safely then do not attempt it.

Walking on Pressed Metal Tile Roofs

To prevent damage to pressed metal tiles the best place to walk is in the centre of the tile at the bottom edge, in the 'pan' of the tile 
This is the strongest part due to the design and is supported by both the tile and tile batten underneath.

Walking on Longrun Roofs

To prevent damage to longrun sheets avoid walking on the rib unless your foot is placed directly on the screw head.  Walk in the pan of the sheet where its supported by the timer batten underneath.    


The sheltered area of  a steel roof directly under the panel is considered an Unwashed Area and many steel roof manufacturers are now excluding these areas from the Warranty due to the corrosion that will form here.
This corrosion is formed when slightly corrosive atmospheric dirt builds up in areas protected from rain.
We strongly recommend that these unwashed Areas are kept free of any debris and hosed out regularly in addition to Bio-Shield application to the topside of the panels


For a successful DIY job, preparation is the key. Following these simple steps will ensure a professional looking finish and long lasting protection against regrowth blocking sunlight from the panel..

Place your ladder on firm ground at the point preferably where the distance between roof and ground is smallest. For every four metres in height the ladder base should be placed 1 metre out from the spouting. The top of the ladder should extend at least 1 metre above the edge of the roof to make entering and exiting the roof as safe as possible.
Placing the ladder against the spouting brackets will reduce the possibility of breaking PVC spouting or deforming metal spoutings.
The first trip up the ladder should be to tie it to the spouting, ideally with a bungee cord or luggage tie to prevent the ladder from slipping. Coloursteel or painted spoutings should have some protection placed between the spouting and ladder to stop scratching of the coating.

Remove any loose debris, tree leaves etc, from under the panels.  Hose out the area with clean fresh water and allow to dry.

Check local governing body regulations for discharge of wash water into the storm water system.
If you are on tank water disconnect the tank from the roof. It will need to stay disconnected for 2 to 4 weeks, and until the roof is flushed by enough rain to remove all traces of the Bio-Shield from the run off water. Do not reconnect the tank until the water is free of frothing or odour.

Check the weather forecast, or rain radar - no rain for 3 to 4 hours
Air temperature above 10 degrees C° will help to accelerate biocidal action.
Premix the Bio-Shield® 1 part to 20 parts water in a pressure sprayer.

If using the Jet-Stream Applicator, follow the instruction on the back label.

Bio-Shield® Mixing Ratios - for Pressure Sprayers

Clean WaterBio-Shield ConcentrateDiluted Bio-Shield
1 Litre50 ml1.05 Litres
10 Litres500 ml10.5 Litres
15 Litres750 ml15.75 Litres
20 Litres1 Litre21 Litres


If you have a respirator, now is the time to put it on, along with a pair of gloves and soft soled shoes and/or a pair of long pants. If you don't have a respirator, try to stay upwind during application. Evaporation of the solution on a warmer day will generate vapor that should be avoided where possible.

Application is best done on an overcast day at any time of the year, or early morning and late afternoon in summer if a warm sunny day is forecast. This slows evaporation and speeds the treatment process.

Saturation, then keeping the surface wet for 10 to 15 minutes is the Key to Success

Fill your sprayer with the premixed Bio-Shield® solution and pump it up to pressure.

Ensure the lichen growths are saturated, with penetration of the solution to the substrate.

Apply a second lighter coat after 10 to 15 minutes to any areas with black algae. 

This second coat is essential to ensure a good clean up of these algae.

Clean Up

Over the next few days the lichens will begin to change color as they  die off.

For the initial clean up, it may take 3 to 6 months for the panels to fully clean up as rain progressively washes the dead growths away.

Clean up times are dependent on how much growth is on the panel and the amount of rain that falls.


Once your panels are clean, Bio-Shield will give optimal protection with regular treatments.

Best practice is to reapply Bio-Shield at the first signs of re-growth. Typically this will be every 2 to 3 years. 

The two or three yearly applications will be easier, faster and with a spread rate up to 8m2 per diluted litre, will use less solution. Any light new growths will die off and the panels will clean up quickly.