Cleaning anti-reflective coating (ARC) on solar panels can be done safely, but only if you skip wet-contact scrubbing and unverified chemical cleaners. Laboratory testing has found that some cleaning agents can cut module performance by up to 5.6%, which is reason enough to treat cleaning as a controlled operation rather than routine housekeeping. Start with water-first methods, and before you scale any robotic or chemical cleaning program across a fleet, run a small field trial first.
TL;DR:
- Using chemical cleaners, especially strong acids and solvents, can permanently damage ARC coatings and reduce panel performance by up to 5.6 percent.
- Wet-contact scrubbing and abrasive tools are prohibited by most manufacturers, with water quality, pressure limits, and chemical approval strictly enforced.
- Robotic cleaning can cause ARC damage depending on robot design and coating type, so on-site testing with pilot trials is essential before scaling.
- Routine cleaning should rely on rain and dry methods within the manufacturer’s specified frequency, escalating only for heavy soiling or bird droppings.
- Conducting controlled pilots on specific module and robot pairs provides the best safety assurance for ARC protection and performance preservation.
Table of Contents
- Why anti-reflective coatings are vulnerable to damage
- What do manufacturers actually prohibit?
- Can robots damage anti-reflective coatings?
- What water and chemicals are safe for ARC cleaning?
- How do you decide when a panel needs cleaning?
- How do you catch ARC damage before it spreads?
- BrightView’s take on protecting ARC while cleaning at scale
- Run a pilot before you commit a fleet to any cleaning method
- Sources
- FAQ
Why anti-reflective coatings are vulnerable to damage
ARC layers are thin. That’s the whole problem. A coating measured in nanometres has almost no margin for chemical attack or physical abrasion, and both degrade it in different ways. Chemical damage happens when a cleaning agent reacts with the coating material itself, etching or stripping it at a molecular level. Abrasion is more straightforward: a brush, squeegee, or grit-laden cloth physically wears the surface down, pass after pass.
Not every mark on a panel means the coating is failing. Rainbow-tinted patches and brown pollen staining often clear up on their own once sunlight and heat do their work, so jumping straight to an aggressive clean over a cosmetic mark can cause more harm than the mark itself.
Statistic to watch: Fraunhofer CSP’s lab testing found some commercially available cleaning agents permanently damaged ARC and reduced power output by up to 5.6% in the worst cases tested. That’s a meaningful chunk of a module’s output lost to the wrong bottle of cleaner.
What do manufacturers actually prohibit?
First Solar and JA Solar both publish cleaning guidance, and the two documents agree on the fundamentals even though the wording differs.
- Wet-contact scrubbing is out. First Solar’s application note prohibits simultaneous water contact and scrubbing or wiping on ARC glass. Squeegees and sponges under wet conditions are named risks.
- Abrasive tools and hard scraping are banned. JA Solar’s cleaning manual rules out abrasive cleaners and hard tools outright, and specifies that the hard side of a two-sided sponge must never touch the glass.
- Water quality and pressure have limits. Both manufacturers set boundaries on water pressure, and JA Solar’s document flags hard water as a source of mineral deposits that dull the surface over time.
- Strong acids, alkalis and solvents need explicit sign-off. Nothing in either manufacturer’s guidance permits aggressive chemical families unless the product has been specifically cleared for that panel range.
- Soft tools and low-pressure water are the approved middle ground. Non-woven soft cloths, low-pressure water spraying, and dry cleaning up to a stated frequency limit sit inside both manufacturers’ rules.
Pro Tip: Keep the manufacturer’s cleaning document on file for every module range on site. Warranty claims get complicated fast when a cleaning contractor can’t show which method was used against which specification.
Can robots damage anti-reflective coatings?
Yes, and the risk isn’t uniform. Robotic cleaning introduces mechanical contact at scale, and how much damage that contact does depends on the brush material, contact pressure, and the specific ARC formulation on your modules. Field research on robotic cleaning tracked multiple module types over 18 months and found some lost more power as cleaning frequency increased, while others showed no measurable change. Same schedule, different outcomes, purely because the coatings and robots involved varied.
That’s why industry guidance from PV‑Tech is blunt about the fix: test the pairing, don’t assume it. A practical trial looks like this:
- Select a representative sample of modules covering each ARC type and mounting configuration on site.
- Set the robot’s brush type, contact pressure and pass count to the settings you intend to use fleet-wide.
- Record baseline photos and electrical output before the first cleaning cycle.
- Run the trial for a defined period, typically several weeks or a set number of cycles.
- Compare post-trial photos and output readings against baseline, watching for hazing, micro-scratching or output drift.
Softer brush materials, lower contact pressure, reduced speed, and longer intervals between cleans all lower abrasion risk. None of those settings are universal, which is exactly why the trial step can’t be skipped.
Pro Tip: Log the trial data against module serial numbers, not just site names. If a coating issue shows up eighteen months later, you’ll want to trace it back to a specific robot configuration, not a guess.
What water and chemicals are safe for ARC cleaning?
Deionised or low-total-dissolved-solids water is the safer default. Hard water leaves mineral deposits behind as it dries, and those deposits sit on the surface degrading light transmission in exactly the way the coating is meant to prevent.
On chemicals, the rule is narrower than most sites assume:
- Avoid strong acids, D-limonene-based degreasers, and aggressive solvents; these have been linked to measurable ARC damage in testing.
- Mild alcohol solutions can work for small, targeted spot cleaning, but only where the manufacturer has confirmed compatibility.
- Never trust a “material compatible” label at face value. Compatibility claims are sometimes tested against standards that don’t reflect your specific ARC formulation, so seek written manufacturer confirmation or run a sacrificial-panel test before deploying any commercial cleaner across a fleet.
How do you decide when a panel needs cleaning?
Rain handles a surprising amount of general dust on its own, and relying on it is often the safer default over reactive cleaning. Heavy soiling and bird droppings sitting on active strings are the exceptions worth acting on, since droppings can create hot spots that outlast any coating concern.
- Check whether rainfall in the past two to four weeks has been adequate for the site’s dust profile before scheduling a clean.
- Stick to dry cleaning within the manufacturer’s stated frequency limit for routine soiling.
- Escalate to wet or robotic cleaning only for soiling that dry methods and rain clearly haven’t shifted.
- Record module ID, soiling type, method used, water specification, robot settings if applicable, and output checks before and after.
How do you catch ARC damage before it spreads?
Electrical checks are your earliest warning system. Take Pmax and Isc readings on trial modules before and after each cleaning pass, and keep that data next to dated photographs, not filed separately where nobody cross-references them.
A single reading tells you little; the trend across cycles tells you everything. Fraunhofer CSP’s testing put worst-case damage at 5.6% power loss, so a drop anywhere near that range after a cleaning cycle is not noise, it’s a signal. If output falls beyond your normal soiling-and-recovery pattern, stop cleaning that pairing immediately and get manufacturer or independent lab input before running another pass.
BrightView’s take on protecting ARC while cleaning at scale
Chemical shortcuts are the fastest way to trade a dusty panel for a permanently degraded one, and that trade rarely gets noticed until the output data is already down. Brightview Solar & Groundskeeping runs water-first cleaning as the default, precisely because it sidesteps the chemical compatibility guesswork altogether. Where robotic cleaning is warranted, pilot testing against real module and ARC combinations, not assumptions from a spec sheet, is what sets fleet-wide policy. That combination gives asset managers a documented, measured basis for scaling cleaning operations instead of a hope that the cleaner label was accurate.
— BrightView
Run a pilot before you commit a fleet to any cleaning method
There are other paths to a cleaner solar fleet, dry-brush contractors, generic wash-down crews, chemical spray services, but none of them give you trial data on your specific ARC and robot pairing before you’re locked into a program. On-site robot and module pilots pair a defined cleaning protocol with post-trial performance reporting, so you see the Pmax and Isc numbers before deciding whether to scale.
The engagement model follows the same logic as the trial protocol above: a pilot first, then a recommended cleaning regime built from your own site’s data, then an ongoing maintenance contract if the numbers support it. No fleet-wide commitment happens before the evidence does. If you manage solar assets across multiple sites, the fastest way to know whether your current cleaning approach is safe for your ARC is to see the pilot options for robotic solar panel cleaning and request a trial scoped to your modules.
Sources
- Fraunhofer CSP warns some cleaning agents may reduce PV module performance by up to 5.6% – pv magazine Global
- Module cleaning guidelines – First Solar (application note PDF)
- Cleaning Method of ARC glass of photovoltaic modules – JA Solar (manual PDF)
- PV cleaning robots: new test methods for a new technology – PV‑Tech
FAQ
Can you clean anti-reflective coating on solar panels without damaging it?
Yes, provided you avoid wet-contact scrubbing, abrasive tools, and unverified chemical cleaners, and stick to manufacturer-approved low-pressure water or soft dry-cleaning methods.
What cleaning agents damage ARC the most?
Strong acids, D-limonene-based degreasers, and aggressive solvents carry the highest risk; Fraunhofer CSP testing linked some commercial agents to power losses of up to 5.6%.
Are robotic cleaners safe for ARC-coated panels?
Not automatically. Abrasion risk varies by robot design and coating type, so a field test on your specific robot and module pairing is needed before fleet-wide use.
How often should ARC-coated solar panels be cleaned?
Frequency should follow the manufacturer’s stated dry-cleaning limit, escalating to wet or robotic cleaning only when rainfall and routine dry cleaning haven’t cleared heavy soiling.
Does Brightview Solar & Groundskeeping clean anti-reflective coated panels safely?
Brightview Solar & Groundskeeping uses water-first methods and runs pilot trials on robot and module pairings before recommending a cleaning regime, which limits chemical exposure and abrasion risk.
