Do solar panels need cleaning?

One of the benefits of installing solar panels is that they require little in the way of maintenance and cleaning. However, solar panels will perform better if they are perfectly clean. The questions is: How much better? And, is professional solar panel cleaning worth it?

Solar panels typically don’t need regular cleaning, rainfall is often enough to free the surface of the panels of dirt and grime. The exception is for solar panels that are installed at a tilt of 10° or less, in this situation, it is recommended you clean your panels as rainfall is less effective at cleaning them.

There are circumstances where panels will benefit from a clean. Every install is different and no one environment is the same. Neighbouring households may have very different installs. A really important aspect of solar panel maintenance is physical inspection and monitoring. By monitoring performance and physically inspecting your panels, you can likely gauge if your system will benefit from a clean.

Does cleaning solar panels make a difference?

It is true that the cleaner your panels are, the more efficient they are and the more electricity they will produce. The improvement in efficiency is the cause of some debate, typically though, for good installations, the improvements in efficiency are often very small.

The effect cleaning solar panels has on output varies depending on site-specific conditions and how dirty your panels are! For our solar power calculations, we conservatively estimate the effect of dirt and grime on panels to account for a 5% loss in output. The 5% de-rating is deemed an acceptable figure to use according to the Clean Energy Council.

Study finds that impact of cleaning is minimal

In Australia, a study conducted in Wollongong concluded that the impact of uncleaned panels on solar output was in the order of 1%, and therefore negligible.

You should clean your panels if they have no tilt

If your panels are installed at an angle below 10°, you should consider regular cleaning. A google study found that output improved by 100% after cleaning their panels for the first time in 15 months – these panels were installed flat with no tilt. A second clean eight months later improved output by 36%. Interestingly, the same study concluded that the improvement in output from cleaning the rooftop panels installed on an angle was negligible.

The Wollongong and Google studies both conclude that, cleaning solar panels installed on an angle has very little impact on their efficiency and output.

How much does it cost to clean solar panels?

To have your panels professionally cleaned, expect to pay at least $150. Solar panel cleaning costs are typically calculated on a per panel basis and range from $12 – $18 per module. If you have a large system with lots of panels, you may get a discount. If access to the roof is more difficult, expect to pay a little more.

The table below shows the cleaning cost range for different size solar panel systems:

If you decide to clean the panels yourself, there are only incidental costs for soap, a squeegee and a suitable brush. However, you should consider the risk that you cause damage to the panels and the cost of your time to perform the clean.

Is professional solar panel cleaning worth it?

When evaluating if a professional solar panel clean is worth it, you should weigh up the cost vs the potential savings benefit. If you pay a cleaning professional, is the improvement in output going to pay for the minimum $150 cost to clean the panels? Let’s take a look using the example of a 6.6kW system in Sydney:

System details:

• 6.6kW system
• Location: Sydney
• Electricity bill: $600 / qtr
• Annual production 9,291 kWh
• Annual savings $1,240

If after cleaning production improves by 5% to 9,694 kWh per annum, annual savings increase to $1,279 – a difference of $39. The increase in savings doesn’t go close to paying for the cost of the clean. Solar production would likely need to improve by 25 – 30% to offset the cost of cleaning the panels.

*Assumptions have been made about the property, electricity use and the system.

Even if you clean the panels yourself, is the time and effort and risk to your safety worth the potential savings?

How to tell if your panels need a clean

There are two ways that you can tell if your panels need to be cleaned:

• 1. Physical inspection
• 2. Monitoring your system’s output

The best way to tell if you should clean your panels is to inspect them. If dirt and grime is highly visible, or if you can see leaf litter and animal droppings, then more than likely they could do with a clean.

If you have a smart monitor, you can monitor your system’s solar output to determine if your panels may benefit from cleaning. Below is a list of items that may impact on the output of your solar panels:

• Dust
• Leaf litter
• Pollen
• Bird / animal droppings
• Traffic film
• Salt
• Lichen

Do-it-yourself cleaning

If you want to clean your solar panels yourself, you need to do so with caution. It is not we recommended. You need to ensure your system is switched off, and you can safely access your panels. Be careful not to scratch the surface of the panels and avoid cleaning when the sun is shining brightly on them.

If your panels are installed on a decent tilt, it’s likely you’ll get little benefit from the clean, so please, weigh up the safety risks beforehand.

Solar panel cleaning preventative measures

If you can install your panels on your roof at a tilt greater than 10° and position them where they are free of shading from trees, you will prevent the likelihood that you will need to regularly clean your solar panels.

Not only will the solar shading from trees reduce the output of your panels, but leaf litter and animal droppings are more likely to be an issue from an overhanging tree.

How often do solar panels need cleaning?

How often you need to clean your panels really comes down to how dirty they get. Our analysis of the benefits of cleaning show that for the clean to be worthwhile, the panels need to be seriously underperforming. If your panels are installed on an angle greater than 10°, they will do a pretty good job cleaning themselves. If panels are installed flat, or you are fastidious about maximising efficiency, it is recommended to clean them every 6 months to 2 years.