Solar panels are a long-term investment in reducing your power bills, but their efficiency can be impacted by soiling from dirt, dust, and other debris. Whether or not solar panels need cleaning depends on several factors, including location, tilt angle, and weather conditions.
This article examines the impact of soiling on energy output, the cost of energy compared to the cost of cleaning, and manufacturers’ guidelines for optimal maintenance.
The Impact of Soiling on Solar Panel Efficiency
Soiling refers to the accumulation of dust, bird droppings, pollen, and other debris on the surface of solar panels. This layer can block sunlight and reduce the efficiency of the panels, leading to energy production losses.
Studies indicate that on average energy output losses from soiling can be expected to be around 2-5% per year. Although this varies depending on environmental conditions and panel tilt. In extreme cases, such as areas with high dust accumulation or heavy pollution and limited rainfall efficiency losses can reach up to 20-30% if left uncleaned for long periods.
Cost of Energy Loss vs. Cost of Cleaning
To determine whether solar panel cleaning is worthwhile, you really should compare the potential energy loss from soiling against the cost of cleaning services. In doing so, all of the following factors play a role:
- Electricity Cost: If the cost of daytime electricity is high, even a small soiling loss could translate to a financial loss worth addressing.
- System Size: Larger solar systems lose more absolute energy when soiling occurs, making cleaning more beneficial.
- Cleaning Costs: Professional cleaning services typically charge between $100-$300 for a 5kW solar system, per cleaning session. While DIY cleaning may require an initial investment in cleaning supplies and safety equipment.
For a typical 5kW residential Sydney or Newcastle solar installation, generating around 7,300 kWh per year, a 5% soiling loss results in an energy loss of approximately 365 kWh annually. If electricity costs you $0.25 per kWh, this equates to a loss of around $91 per year. Even if professional cleaning costs $150 per session and is needed only once a year, the cost of cleaning clearly outweigh the benefits unless significant soiling occurs.
Location Factors Affecting Cleaning Frequency
Different locations experience varying levels of soiling, influencing how often solar panels should be cleaned for example:
- Industrial areas are more prone to pollution and airborne particulates and so panels may suffer increased soiling loss. If you’re property is anywhere near the coal terminals in Newcastle, the power stations on the Central Coast, or the open cut mines in the Hunter Valley you’ll already know how much dust these industries create.
- Rural areas generally have much less airborne pollution, but increased dust can be generated on panels from unsealed roads, particularly in periods of drought.
- Panels in coastal areas can see a build up of salt deposits from ocean spray which can accumulate affecting performance. Although this is generally less impactful than other types of soiling as it tends to block less light. Panels in coastal areas can however, experience soiling from large sea birds, such as pelicans, which can can dramatically affect energy output!
- Frequent rainfall naturally cleans panels in climates with higher precipitation such as Coastal Queensland, Byron Bay and the Northern Rivers, which really reduces the need for manual cleaning.
- Arid and desert regions, such as in Central Australia, north western Victoria and western NSW generally have much lower rain and much higher dust accumulation, so panels in these locations are the most likely to have soiling that justifies panel cleaning.
The image below shows a heavily soiled panel next to an unsealed road in an arid area of Victoria. The soiling losses were found to be above 10%.
Solar Panel Tilt Angle and Self-Cleaning Effect
The tilt angle of solar panels plays a crucial role in reducing soiling. Panels installed at a steeper angle more than 10 degrees are better at shedding dust and debris when it rains. Flat or low-tilt panels are more susceptible to dirt accumulation as water can pool on the surface, requiring manual intervention.
Manufacturers’ Guidelines on Cleaning Frequency
While some modern panels come with hydrophobic coatings that repel dirt and require minimal maintenance, most solar panel manufacturers provide recommendations for cleaning, with common guidance including:
- The allowable water pressure to be used in cleaning a panel. Necessary to check if you are using a high pressure cleaner.
- The types of chemicals that can be used to clean a solar panel.
- The types of brushes that can be used to clean their solar panels. Some materials are more abrasive and have the potential to scratch the surface of the glass.
Whether you decide to clean your solar panels yourself or hire a professional cleaning service, you should always make sure that the manufacturer’s guidelines for cleaning are being followed. This will ensure that your solar panel warranty is preserved. For larger industrial customers there are now also solar cleaning solutions specially developed to keep soiling lower between cleans.
Conclusions on Solar Panel Cleaning
While solar panel cleaning can improve efficiency, whether it will be beneficial depends on location, tilt angle, and soiling levels. Cleaning is not always financially justified unless energy losses are substantial or you are able to safely clean your panels according to the manufacturer’s guidelines. Regular inspections, reliance on natural rainfall, and following manufacturer recommendations can help optimize maintenance while keeping costs low. Consider the following as a a guide to whether your solar panels need cleaning:
- In areas with regular rainfall and panels tilted above 10 degrees cleaning may only be needed once every 6-12 months if at all, and the cost of professional cleaning may not be justified.
- For panels installed at tilt angles below 10 degrees or experiencing lower rainfall, periodic visual inspections can help determine when cleaning is necessary rather than following a rigid schedule.
- For larger systems in dry climates or industrial areas, cleaning may be required every 3-6 months depending on the latest rainfall and tilt angle. Although the effects of cleaning should be observed and compared against the cost to establish the required frequency.
Ultimately the question of whether solar panels need cleaning does not have a one size fits all answer, some installations in some locations will benefit from regular cleaning, while for others it would rarely be financially justified. Its important to consider the factors outlined above and take a “horses for courses” approach.
