How to clean solar panels properly

Keeping your solar panels clean is essential for maintaining peak efficiency and maximising your investment. Dirty panels can lose 15-25% of their power output, directly impacting your electricity savings. This guide provides a safe, warranty-friendly cleaning method that protects your panels whilst restoring optimal performance.

When to clean your solar panels

Visual inspection signs:

• Visible dirt, dust, or debris accumulation
• Bird droppings on panel surfaces
• Pollen coating (common in spring)
• Significant performance drop without other causes

Frequency guidelines:

• Desert areas: Every 3-4 months
• Urban/suburban: Every 6-8 months
• Rural areas: Every 8-12 months
• Coastal regions: Every 6 months (salt spray)

What you'll need

Essential equipment:

• Garden hose with adjustable nozzle
• Soft-bristle brush or sponge
• Squeegee (optional but recommended)
• Mild washing-up liquid
• Clean water bucket
• Non-abrasive cloth or microfibre towel

Safety equipment:

• Non-slip shoes
• Ladder (if needed)
• Safety harness (for roof work)

Avoid these items:

• Pressure washers (can damage seals)
• Abrasive cleaners or scrubbers
• Metal brushes or scouring pads
• Harsh chemicals like bleach

Step-by-step cleaning process

Step 1: Safety first

Turn off your solar system at the DC isolator switch before cleaning. This prevents electrical hazards and protects the system during maintenance.

Step 2: Choose the right time

Clean panels early morning or evening when they're cool. Hot panels can cause water to evaporate quickly, leaving streaks and potentially cracking from thermal shock.

Step 3: Initial rinse

Spray panels with clean water to remove loose dirt and debris. Start from the top and work downward, allowing gravity to help carry away particles.

Step 4: Prepare cleaning solution

Mix a small amount of mild washing-up liquid with water in your bucket. The solution should be barely soapy - too much soap creates residue.

Step 5: Gentle scrubbing

Using a soft brush or sponge, gently clean the panel surface in circular motions. Pay special attention to stubborn spots like bird droppings or tree sap.

For stubborn stains:

• Soak the area with soapy water for several minutes
• Use a plastic scraper for hardened debris
• Never use metal tools that could scratch the glass

Step 6: Thorough rinse

Rinse all soap residue with clean water. Soap left on panels can attract more dirt and reduce efficiency.

Step 7: Squeegee and dry

Use a squeegee to remove excess water, working from top to bottom. Finish with a clean, lint-free cloth to prevent water spots.

What not to do

Never use pressure washers: High pressure can damage panel seals, frames, and electrical connections.

Avoid walking on panels: Even tempered glass can crack under concentrated weight.

Don't clean hot panels: Thermal shock from cold water on hot glass can cause cracking.

Skip harsh chemicals: Bleach, ammonia, and abrasive cleaners can damage anti-reflective coatings.

Don't ignore safety: Roof work requires proper safety equipment and technique.

Professional cleaning vs DIY

When to DIY

• Ground-mounted systems
• Single-story installations with safe access
• Comfortable working at height
• Regular maintenance cleaning

When to hire professionals

• Multi-story roof installations
• Steep or complex roof designs
• Heavy soiling requiring specialised equipment
• Safety concerns or physical limitations

Professional cleaning typically costs £100-£300 depending on system size and access difficulty.

Maintaining efficiency between cleanings

Monitor performance: Track your system's output through monitoring apps or monthly bills. Sudden drops may indicate cleaning needs.

Trim nearby vegetation: Overhanging branches drop leaves and provide bird perches above panels.

Install bird deterrents: Mesh guards can prevent birds from nesting under panels without harming wildlife.

Consider coating options: Some anti-soiling treatments can reduce cleaning frequency, though they require professional application.

Regional considerations

Coastal areas

Salt spray requires more frequent cleaning and thorough rinsing to prevent corrosion of metal components.

Agricultural regions

Dust from farming operations and pollen can accumulate quickly during growing seasons.

Urban environments

Air pollution and particulates may require more frequent cleaning in heavily trafficked areas.

Desert climates

Dust storms and minimal rainfall mean more frequent cleaning but less organic growth.

Warranty considerations

Most solar panel warranties remain valid with proper cleaning, but verify your specific terms. Key points:

• Use only manufacturer-approved cleaning methods
• Document cleaning activities and dates
• Report any damage immediately
• Follow installer guidelines for roof access

Signs your panels need professional attention

Contact a qualified technician if you notice:

• Cracks in panel glass or frames
• Loose or damaged mounting hardware
• Burn marks or discoloration
• Persistent performance issues after cleaning
• Water intrusion or condensation inside panels

Maximising cleaning effectiveness

Time cleaning with weather: Clean before expected rain to take advantage of natural rinsing.

Check inverter alerts: Many systems alert you to performance issues that cleaning might resolve.

Combine with inspection: Use cleaning time to inspect mounting hardware and connections.

Keep records: Document cleaning dates and any issues discovered for warranty and maintenance purposes.

Regular cleaning is a small investment that protects your larger solar investment. With proper technique and safety precautions, most homeowners can maintain their panels effectively whilst avoiding damage and preserving warranties.