8 Signs Your Solar Panels Need Cleaning
Most property owners look up at their roof and think their panels look fine. They usually don't — and the loss in energy output proves it. Here's how to know.
If even one of these applies to your property, your system is almost certainly producing less than it should be. Most are easy to spot from the ground — no ladder required.
Reason 01
Spring Pollen Blanket
Wisconsin's oak and birch pollen creates a sticky biofilm that bonds to glass. Light rain redistributes it; it doesn't wash away. By late May most untreated systems are operating at 75–85% of their rated capacity.
Reason 02
Hard Water Spots
Wisconsin averages 18–20 grains of hardness. When sprinklers, dew, or rain dries on your panels, calcium and magnesium minerals etch into the glass and refract sunlight away from the cells. Standard hose water makes this worse.
Reason 03
You Live Near Farms or Open Fields
Southern WI and Northern IL are heavy ag country. Tilling dust, fertilizer aerosol, and crop residue ride the wind for miles and settle on south-facing roofs. If you can see a corn or bean field, your panels are in the drift zone.
Reason 04
Visible Bird Droppings
A single dropping doesn't just block light — it creates a "hot spot" where the cell underneath overheats. Long-term, this can permanently damage cells and shorten panel lifespan. Spot-cleaning is not enough; the surrounding film matters too.
Reason 05
Your App Shows Lower kWh Than Usual
Compare this week's daily production to the same week last year. If it's down more than 5–10% with similar weather, soiling is the most likely cause. (Natural panel degradation is only ~0.5% per year — anything more sudden than that is dirt.)
Reason 06
Wildfire Smoke Reached Your Area
The 2023–2025 Canadian wildfire seasons deposited fine ash across the Midwest. The particles are too small to see and too sticky to rinse off. If you remember orange skies or air quality alerts, your panels are coated.
Reason 07
Near a Busy Road or Recent Construction
Road salt spray, diesel particulate, roofing dust, and concrete dust all bond chemically to panel glass. Even neighborhood construction half a block away can leave a measurable film on your system within days.
Reason 08
It's Been 12+ Months Since the Last Cleaning
NREL recommends professional cleaning at least once a year for U.S. systems, and twice a year in pollen-heavy or agricultural regions. If you can't remember the last time, you're overdue.
Important
Thinking of doing it yourself? Read this first.
Cleaning a solar panel sounds simple. It isn't. Pressure washers crack micro-cells. Tap water leaves mineral spots that permanently etch the glass. The wrong soap strips the anti-reflective coating that took the manufacturer years to engineer.
Improper cleaning can void your warranty — on a system that often costs $20,000 to $40,000+.
If you're going to do it yourself, please know what you're doing first. Read the manufacturer's official cleaning guidelines for your panels (Tesla, SunPower, LG, LONGi, JinkoSolar — we've compiled all of them on one page).
How a professional cleaning works
Every clean follows the same protocol the manufacturers themselves recommend — no shortcuts.
Soft rotary brushes
No abrasion, no micro-scratches
100% deionized water
Zero mineral residue, no spots
Biodegradable soap
Manufacturer-approved formula
Cool-panel timing
Cleaned in the early morning or evening
Fully insured
Roof, panels, and inverter all covered
Before & after photos
You see exactly what we did