How to Clean Solar Panels: The Right Way
- Dirty panels lose 5–15% of output — cleaning is one of the highest-return maintenance tasks.
- Clean in the early morning or evening — never in full midday sun (thermal shock risk).
- Use water and a soft brush or sponge — never abrasive materials or harsh chemicals.
- Never use a pressure washer — it can penetrate the frame seal and destroy the junction box.
- In most locations, 1–2 cleanings per year is sufficient. Dusty and pollen-heavy areas may need more.
How much does soiling affect output?
| Soiling type | Typical output loss | Cleaning frequency needed |
|---|---|---|
| Light dust (normal accumulation) | 2–5% | 1–2× per year |
| Heavy dust (desert, road proximity) | 10–25% | Monthly |
| Pollen (spring season) | 5–10% | After pollen season |
| Bird droppings (partial shading effect) | 10–30% per affected cell | As soon as noticed |
| Wildfire ash | 15–40% | Immediately after ash fall |
| Snow (complete coverage) | Up to 100% | Clear when safe to do so |
When to clean — and when not to
- Clean when: You notice sustained output reduction on sunny days, after bird activity, after pollen season, after dust storms or ash events, and as part of your annual maintenance.
- Don't clean when: Rain is forecast in the next day or two (let rain do the work), during high wind (wet panels + high wind = panels acting as sails), when panels are hot in full midday sun.
What you need
- Garden hose with gentle spray nozzle (no jet or pressure washer)
- Soft-bristle brush or sponge on an extension pole (for roof panels)
- Bucket of clean water — add a few drops of mild dish soap for heavy soiling
- Soft squeegee (optional) for streak-free finish
- Safety harness if cleaning roof-mounted panels
Step-by-step cleaning process
- Choose the right timeClean in the early morning before the sun heats the panels, or in the evening after they've cooled. Avoid cleaning in full sun — cold water on hot glass can cause thermal shock and micro-cracks. Early morning is ideal as the panels are cool and any remaining water evaporates quickly.
- Rinse with water firstSpray the panels with water to loosen and remove loose dust and debris. This prevents the dry particles from scratching the glass when you wipe. A gentle spray from a garden hose is sufficient — do not use a jet setting or pressure washer.
- Wash with soft brush or spongeUsing a soft-bristle brush or non-abrasive sponge with clean water (or mild soap solution for heavy soiling), gently scrub the panel surface. Work in straight lines from top to bottom. Use an extension pole for roof panels to avoid climbing.
- Pay special attention to edges and cornersDust and pollen tend to accumulate at the lower edge of the panel frame. Use the brush edge to clean along the frame border where the glass meets the aluminium.
- Rinse thoroughlyRinse with clean water to remove all soap residue. Soap residue left on the panel surface dries as a film that attracts more dirt — defeating the purpose of cleaning.
- Allow to air dry or squeegeeLet panels air dry or use a clean soft squeegee for a streak-free finish. In hard water areas, squeegee or use deionised water for the final rinse to prevent mineral deposits.
Removing stubborn deposits
Bird droppings
Dried bird droppings are difficult to remove with water alone. Soak with a wet cloth for 5–10 minutes to rehydrate, then gently wipe away. Do not scrape with anything hard. A few drops of white vinegar on the cloth helps dissolve the deposit without damaging the glass.
Tree sap
Isopropyl alcohol (rubbing alcohol) on a soft cloth dissolves tree sap effectively. Apply, let sit for 30 seconds, then wipe gently. Follow with a water rinse to remove any residue.
Mineral deposits (hard water spots)
Hard water leaves white mineral deposits after evaporation. A diluted white vinegar solution (1 part vinegar, 3 parts water) dissolves calcium and magnesium deposits. Apply, wait 2 minutes, scrub gently, rinse thoroughly. Use deionised water for the final rinse to prevent re-deposit.
Cleaning ground-mounted and RV panels
Ground-mounted panels are the easiest to clean — no heights involved. The same process applies. Tilt the panels to a steeper angle during cleaning if possible to help water and debris run off. After cleaning, return to optimal angle.
For RV and van roof panels: clean from a step stool or low ladder if possible. If panels are on a high roof, use an extension-pole brush from ground level. Do not climb on the RV roof unless it's rated for walking — many fibreglass roofs are not.
Snow removal
Snow-covered panels produce zero output. Removing snow is worthwhile if panels will be covered for more than a day and sunshine is forecast:
- Use a soft snow rake or foam-head squeegee — never metal tools or ice scrapers
- Work from the bottom of the panel upward to pull snow off, not push it across the glass
- On steeply tilted ground mounts, snow slides off naturally when sun hits the panel — often no intervention needed
- Don't stress about a thin snow layer — it often slides off quickly once the panel warms slightly
Does rain clean panels?
Light rain does rinse loose dust from panel surfaces. However, rain often leaves mineral deposits and bird dropping residue — it doesn't replace manual cleaning. In areas with regular rainfall (Pacific Northwest, Northeast), panels stay cleaner and may only need one manual cleaning per year. In dry climates (Southwest, California), rainfall is too infrequent to substitute for cleaning.
Frequently asked questions
Can I use a car wash brush or household mop on solar panels?
Only if the brush is genuinely soft-bristle and designed for delicate surfaces. Many car wash brushes are stiffer than they look and can scratch the anti-reflective coating. When in doubt, use a dedicated solar panel cleaning brush — they're inexpensive and specifically designed for the task.
Will cleaning solar panels void the warranty?
Not if done correctly. All major manufacturers allow and recommend regular cleaning. Using abrasive materials, pressure washers or harsh chemicals can void the warranty if physical damage results. Follow the manufacturer's cleaning guidelines in your panel documentation.
How do I know if my panels need cleaning?
The best indicator is output data. If your charge controller shows significantly lower output on a sunny day compared to previous sunny days under similar conditions, soiling is a likely cause. If you have remote monitoring, output trends are easy to track. See our remote monitoring guide.