Learning how to remove lichen from solar panels is critical because lichen is not just dirt—it is a living, symbiotic organism… Unlike dust, simple water and scrubbing are not enough to remove it. Lichen causes severe “hard shading,” which kills system output. Safe removal requires a specialised biocide treatment to chemically sever the root system without damaging the panel’s delicate anti-reflective coating.
If you have noticed crusty, pale green or white spots spreading across your solar array, you are dealing with one of the most stubborn threats to solar efficiency in Australia: Lichen.
As a Senior Solar Maintenance Specialist, I have inspected thousands of systems from Queensland to Victoria. The most common cause of permanent panel damage I see isn’t hail or debris—it is well-meaning homeowners trying to scrape lichen off their panels with the wrong tools.
Lichen is deceiving. It looks like a surface stain, but it is actually an invasive growth that anchors itself into the microscopic valleys of the glass. This guide explains exactly how to remove lichen from solar panels without destroying the technology that generates your power.
Identification: Is it Dirt, Moss, or Lichen?
Before attempting any cleaning, you must identify what is growing on your roof. Dust and grime rinse off easily. Lichen does not.
Lichen is a composite organism arising from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. In simple terms, the algae provides food (via photosynthesis), and the fungus provides structure and protection.
How to spot Lichen on your panels:
- Appearance: Look for “crusty” circular patches. They are often light green, grey, or yellowish-white. Unlike moss, which is soft and fuzzy, lichen is hard and flat.
- Location: It typically starts at the bottom edge of the panel near the aluminium frame, where water pools and dirt collects, before spreading upwards across the glass surface.
- Texture: If you were to touch it (when the system is off and cool), it would feel rough and gritty, almost like cement spots.
Why is it growing on my roof? Lichen thrives in specific conditions that are common across Australia:
- Shade: Solar panels installed near overhanging gum trees or obstructions are prime targets. Lichen hates direct, scorching heat but loves the cool, damp environment created by partial shade.
- Humidity: Coastal areas or regions with high morning dew provide the moisture the fungi need to establish a colony.
- Bird Droppings: This is the catalyst. Bird poop is rich in nitrogen and phosphorous. When birds perch on your panels, they deposit a nutrient-rich “fertiliser” that accelerates lichen growth rapidly.
The Hidden Danger: ‘Hard Shading’ & Hotspots
Many system owners ignore small spots of lichen, thinking, “It’s only covering 1% of the panel; surely I’m only losing 1% of power?”
This is a dangerous misconception regarding solar physics.
Soft Shading vs. Hard Shading Dust and smog create “soft shading.” They reduce the light intensity generally, leading to a linear drop in power. Lichen, however, creates “hard shading.” It is opaque. It completely blocks sunlight from reaching the silicon cells underneath.
Because standard solar panels are wired in series (like old Christmas lights), when one cell is blocked, it acts as a resistor rather than a generator. The current from the rest of the string struggles to push through this blockage. This doesn’t just reduce power from that single panel; it can drag down the performance of the entire string of panels. To understand exactly how much money this efficiency drop costs you, read our analysis on The Real Cost of Soiling.
The Hotspot Phenomenon The most critical risk of lichen shading loss is the creation of hotspots. When a cell is blocked by a dense patch of lichen, the energy from the unshaded cells is forced into the shaded cell, dissipating as heat.
- Thermal Stress: The blocked cell can reach temperatures exceeding 100°C.
- Component Failure: This heat can burn out the panel’s bypass diodes, melt the backsheet, or even crack the glass.
- Permanent Damage: Once a hotspot burns a cell, that panel is permanently degraded. No amount of cleaning will fix it.
The DIY Mistake: Why You Should Never Scrape It
If you take only one thing from this guide, let it be this: Put the scourer down.
I have seen countless high-end solar systems ruined by homeowners using plastic scrapers, razor blades, or steel wool to remove lichen.
The Micro-Peak Bond Solar glass is not perfectly smooth. Under a microscope, it has peaks and valleys designed to trap light. Lichen roots (rhizines) grow into these valleys and secrete acids that chemically bond to the glass.
When you try to mechanically scrape lichen off solar panels, you are shearing off the top of the organism, but the roots remain embedded.
The Risk of Scratches Scraping requires force. Applying force to tempered glass with an abrasive tool causes micro-scratches.
- Destroying the ARC: Modern panels have an Anti-Reflective Coating (ARC) to boost efficiency. Scraping strips this coating, reducing the panel’s ability to absorb light.
- The Dirt Trap: Micro-scratches create a rough surface. Ironically, these scratches act as new anchor points for dirt, algae, and lichen to grow back faster and stronger than before.
Using abrasive force is a short-term visual fix that guarantees long-term efficiency loss.
The Correct Removal Process (Chemical Treatment)
To safely restore your system, you must move away from mechanical force and utilise chemistry. The goal is to kill the organism so it releases its bond with the glass naturally.
Step 1: Application of Solar-Safe Biocide A professional solar panel lichen removal chemical is required. We do not use standard roof moss killers, as many contain harsh sulphates or caustic ingredients that can corrode the aluminium frames or damage the panel seals. Specialised solar biocides (often based on Quaternary Ammonium Compounds) are sprayed liberally over the affected areas. These agents penetrate the cell walls of the lichen and the algae symbiont.
Step 2: Dwell Time This is the step most DIYers miss. You cannot spray and wipe immediately. The chemical needs “dwell time” (usually 15 to 30 minutes, depending on the severity) to soak into the lichen structure. During this time, the biocide kills the root system. As the organism dies, it loses its structural integrity and its grip on the glass micro-pores softens.
Step 3: Rinse and Soft Agitation Once the lichen is dead and the bond is broken, we use a soft, rotating solar brush and de-ionised water to gently agitate the surface. The lichen should slough off without aggressive scrubbing. If the infestation is severe (years of growth), it may require two treatments. It is better to treat it twice gently than to treat it once aggressively.
WARNING: Do NOT use Vinegar. A common internet myth suggests using vinegar for cleaning. Vinegar is acidic and can damage the chemical composition of the Anti-Reflective Coating and corrode the metal clips holding your panels.
Prevention: Stopping the Regrowth
Once your panels are clean, you need to ensure the lichen doesn’t return in six months. Moss on solar panels in Australia is persistent, but manageable with the right strategy.
1. Environmental Management Look at the trees surrounding your roof. Are branches casting shade on the panels during the morning or late afternoon? Trimming these branches back not only increases your solar production but also reduces the humidity and organic matter (leaves/sap) falling on the panels, starving the lichen of its environment.
2. Install Bird Proofing As mentioned, bird droppings are the super-food for lichen. If you have pigeons or mynas nesting under your array, you have a lichen factory on your roof. Installing high-quality mesh skirting around your system prevents birds from nesting underneath and drastically reduces the amount of droppings on the glass.
3. Regular Maintenance Schedule Lichen grows slowly at first, then explodes. A programmed maintenance clean every 6-12 months ensures that spores are washed away before they can anchor and develop into mature lichen.
Conclusion
Lichen is effectively a “cancer” for your solar system’s efficiency. It eats into your energy production, creates dangerous hotspots, and risks the longevity of your investment.
While it might be tempting to grab a scraper and handle it yourself, the risk of permanently scratching the glass and stripping the coating is too high. This is a biological problem that requires a chemical solution.
Lichen removal is delicate work. Don’t risk scratching your panels.
Lichen removal is delicate work. Don’t risk scratching your panels. Contact Clean Solar Aus today for advice on safe treatment solutions and how to protect your warranty.