Do solar panels need to be cleaned?

The important factors that determine how,
when (and if) your solar panels should be cleaned.

There are 4 main factors that affect the level of soiling (deposits of foreign matter) that accumulate on a solar panel


In solar installations near the ocean, salt quickly creates a crust on panels. Adding to the issue birds can make quite a mess of the surface, which is very damaging as it is not washed away with rainfall (think of the last time you had bird droppings on your car). PV systems near industrial zones, heavy traffic or where major civil works are being undertaken suffer from above average soiling levels.


Wind can be good or bad with regards to soiling. Studies have found that installing panels in locations with high winds can be beneficial as the wind blows a lot of the dust off the panels. However, if the area is both dusty/sandy and windy, the wind blows material onto the surface of the panels², reducing the panel efficiency and increasing the need for  cleaning.


The degree to which the panels are tilted is one of the biggest contributors to efficiency losses on solar systems through soiling¹. Numerous academic studies have shown the flatter the panels, the higher the level of soiling. Residential homes with solar systems quite often have a roof pitch of 20-30 degrees and as such do not accumulate the same amount of grime as their flat-roofed counterparts in the commercial sector.


Heavy rain can be beneficial in reducing accumulation of large particles (ie pollen) on panels³. However, it is not effective at removing smaller dust particles. The best example of this is looking through the windscreen of your car after light rain. A study concluded that, on panels with a 30-degree tilt, at least 20mm of rainfall is required to clean the surface, whilst a light, drizzly rain actually makes the soiling worse4. The study also found that the lower the tilt of the panels, the less effective rain was in washing away accumulated dirt and grime.

CSM’s efficiency calculator will help you determine how much power you are losing through soiling, so you can make an informed decision on when/if you get your panels cleaned.

So how much efficiency is lost through dirty panels?

As discussed above, there is no generic answer for this. It is totally dependent on the tilt of the panels, the weather conditions and the site location. A comprehensive study5 concluded that panels tilted at 30 degrees showed losses of between 1-8% from soiling. However, on relatively flat modules (such as in most commercial applications) the efficiency losses were between 8-22%. So, if you have a dirty 100kW system, it may only be generating as much as the clean 80kW system next door. Depending on your tariff, system size and level of dirt build up, this can equate to an additional $1,800 per month on your energy bill because your panels aren’t clean!6 Whatever your situation, CSM’s efficiency calculator will help you determine how much power you are losing through soiling, so you can make an informed decision on when (or if) you need to get your solar system cleaned.

How should panels be cleaned?

Solar Panel Manufacturers’ all stipulate how their panels should be cleaned. Generally, the use of harsh scrubbing equipment,pressure hoses and chemicals are not permitted as they may damage the panels and void the warranty. Timing is important too. Manufacturers recommend that panels should be cleaned before or after the system reaches maximum working temperature, as applying cool water over hot panels can cause cracking- reducing the life of the panel. PV Modules should only be cleaned with specifically designed equipment. CSM Australia uses only de-ionised water and soft, water-fed brushes to clean panels in accordance with manufacturer’s instructions. De-ionised systems remove minerals and salts from tap water and are also used to clean large windows (as they leave the glass with a clean, streak-free finish). These units are expensive to purchase and maintain, but provide a far better finish, require no chemicals and are safe for rainwater collection.

If it doesn’t make economic sense to do the job, we’ll tell you. That’s our promise!   

Does it make financial sense to clean my panels?

This is where CSM Australia is different to a lot of other cleaning companies. We have developed a program that uses 30 years of BOM data to model the expected solar generation of a PV system and calculate site-specific degradation losses based on tilt of the panels, the level of soiling and the age of the system.

We then input your current bundled c/kWh energy charges into the model and produce a report that shows when/if you should have the system cleaned and the forecasted Return on Investment (ROI). If the model shows it is uneconomical to clean the panels, then we will advise against it. Believe it or not, CSM Australia values safety, and have a strong and we have turned down work because it did not make economic established Health, Safety and Environmental management sense to perform the clean!

Why choose CSM for your next clean?

The team at Commercial Solar Maintenance have many years of experience in the solar industry and have in-depth knowledge of solar maintenance requirements. We specialise in Commercial Solar, and can quote for a one-off clean, or provide complete O&M plans to large commercial installations and solar farms. Unlike solar retail companies who can use cleaning as a “lead generator” to push additional panels or upgrades onto customers, we will not sell you a solar system or upgrade. If an issue is found during our inspection, we will provide a report and suggestions on what needs to be remedied -but we will not try to sell anything to you.

CSM Australia values safety, and have a strong and established Health, Safety and Environmental management system. We are fully insured and have our own in-house team who are qualified in working at heights and trained in solar cleaning.

Finally, our Solar performance model is unique in the market, allowing you to make a sound financial decision on if or when to get your panels cleaned. If it doesn’t make economic sense to do the job, we’ll tell you. That’s our promise!


CSM Australia services the following locations:

Alice Springs
Sunshine Coast

Coffs Harbour

Wagga Wagga
Mildura- Wentworth

Mount Gambier