Solar Panel Maintenance in the Pacific Northwest: Rain, Moss & More

Solar panels are a great investment in the Pacific Northwest, but our unique climate—rain, moss, and towering evergreens—means maintenance is a little different here than in sunnier states. The good news? With the right care, your solar panels can last 25+ years and keep producing clean energy, even in Oregon and Washington’s famously wet weather.

Here’s what you need to know about solar panel maintenance in the PNW.

Do Solar Panels Work in the Rain?

Yes! Solar panels still generate electricity on cloudy or rainy days, just at a reduced rate. In fact, the Pacific Northwest gets enough sunlight to make solar a smart choice—especially with our long summer days.

Rain can help: Light rain rinses off dust and pollen, keeping panels clean.
Heavy rain or snow: Can temporarily reduce output, but panels are designed to handle it.
Myth busted: Rain does not replace the need for occasional cleaning, especially in the PNW.

The Moss Problem: What You Need to Know

Moss thrives in the PNW’s damp, shady conditions—and it loves to grow on roofs and solar panels. Moss on solar panels can reduce efficiency by 10–30% by blocking sunlight and trapping moisture.

How to Prevent Moss on Solar Panels

| Method | How It Works | Cost | Effectiveness | |--------|-------------|------|---------------| | Zinc or Copper Strips | Metal strips release ions that inhibit moss growth | $50–$200 | High (lasts 5+ years) | | Regular Cleaning | Removes moss before it takes hold | $150–$300/year | High (if done 1–2x/year) | | Anti-Moss Spray | Biodegradable sprays prevent regrowth | $20–$50/year | Medium (needs reapplication) | | Tree Trimming | Reduces shade and moisture | $200–$800 | High (also improves sunlight) |

Pro Tip: If your roof is mossy, clean it before installing solar panels. Moss can damage roof shingles and reduce panel lifespan.

Cleaning Your Solar Panels: DIY vs. Professional

When to Clean Your Panels

1–2 times per year (spring and fall).
After heavy pollen season (spring).
If you notice a drop in output (check your monitoring app).

DIY Cleaning (Safe for Most Homeowners)

Use a soft brush or squeegee with a long handle.
Only use water (no soap or abrasive cleaners).
Avoid high pressure (can damage panels).
Never walk on panels (they’re strong but not designed for foot traffic).

When to Call a Professional

Panels are on a steep or high roof.
Moss or grime is stubborn.
You’re not comfortable on a ladder.

Cost: $150–$300 per cleaning (varies by system size and roof access).

Tree Trimming: The Overlooked Maintenance Task

Trees provide shade, but too much shade = less solar power. In the PNW, evergreens like Douglas firs and cedars can grow quickly and cast shadows over your panels.

When to Trim Trees

If branches are touching or shading panels.
If trees block sunlight for more than 2–3 hours/day.
If leaves or needles pile up on panels.

Cost: $200–$800 (depends on tree size and number of trees).

Bonus: Trimming trees also reduces fire risk and prevents roof damage from falling branches.

Does Rain Really Clean Solar Panels?

Myth: “Rain will keep my panels clean.” Reality: Rain helps, but it’s not enough—especially in the PNW.

Light rain rinses off dust and pollen.
Heavy rain can leave mineral deposits (hard water spots).
Moss and bird droppings won’t wash away with rain alone.

Solution: A quick rinse with a hose 2–3 times per year keeps panels performing at their best.

Other PNW-Specific Maintenance Tips

Check for Snow Buildup (Yes, Even in the PNW!)

Light snow usually slides off on its own.
Heavy snow: Use a soft roof rake to gently remove snow (don’t scrape panels!).
Never use hot water (can crack panels).

Monitor Your System

Most solar systems come with monitoring apps (like Enphase or Tesla).
Check for dips in production—could signal dirt, shade, or a system issue.

Inspect for Damage After Storms

Wind: Check for loose panels or wiring.
Hail: Look for cracks or dents (rare in the PNW, but possible).
Falling branches: Trim trees to prevent damage.

Bottom Line

Solar panels in the PNW need a little extra care—especially for moss and tree shade.
Clean panels 1–2 times per year (DIY or hire a pro).
Trim trees to maximize sunlight and prevent damage.
Rain helps, but it’s not enough—occasional rinsing keeps panels efficient.
Monitor your system to catch issues early.

With the right maintenance, your solar panels will keep powering your home for decades—rain or shine.

Need help with solar panel cleaning or maintenance? Contact us for professional service in Oregon and Washington!