How to Clean Solar Panels Safely (Without Voiding the Warranty)

Solar panels have no moving parts and are built to sit outside for 25+ years, so they need very little upkeep — but a layer of dust, pollen, bird droppings, or ash does cut how much electricity they make.

The good news: cleaning is simple, you rarely need to do it, and in most cases plain water and a soft brush are all it takes. The trick is doing it without damaging the glass or voiding the warranty.

Do your panels actually need cleaning?

Often, no. Rain does most of the work, and on a roof tilted at a typical angle, water sheets off and carries the dust with it. In rainy climates, the energy you lose to dirt — called soiling loss — is usually only 1–5% a year, which rarely justifies climbing on a roof.

Cleaning is worth it when:

• You live somewhere dry and dusty (desert, near farmland, unpaved roads) where rain is rare.
• Panels sit under trees and collect bird droppings, sap, or pollen, which are sticky and don't rinse off.
• There's been wildfire ash, construction dust, or a long drought.
• Your monitoring app shows production has dropped and the glass looks visibly coated.

A quick way to judge the payoff: a 10% output loss on a system that saves you $1,500 a year is about $150 a year — enough to justify an occasional rinse, but not a monthly deep clean. If you're not sure how much you're losing, the solar panel output calculator shows how production scales, and the solar payback calculator puts a dollar figure on it.

What to use — and what to never use

Scratches on the glass are permanent and scatter light, so the golden rule is soft tools only. Hard water leaves mineral spots as it dries, which is why distilled or deionized water gives a streak-free finish.

How to clean solar panels, step by step

1. Pick the right time. Early morning or a cool, overcast day. Cool glass won't thermally shock when water hits it, and you won't get streaks from fast evaporation.
2. Stay safe — clean from the ground if you can. A soft brush or squeegee on an extension pole lets you reach most roof arrays without climbing. If you must go on the roof, use proper fall protection, or hire a pro. Never touch panels near damaged wiring.
3. Turn the system off if your inverter has a shutdown procedure, and avoid cleaning around any exposed wiring.
4. Rinse first. A normal garden-hose rinse removes loose dust so you don't grind it into the glass.
5. Wash gently. Use a soft brush or sponge with plain water, adding a little dish soap or solar cleaner only for stuck-on grime. Work in light strokes — no scrubbing.
6. Rinse again and squeegee. Rinse off any soap and pull a rubber squeegee across to avoid spots. Let the rest air-dry.
7. Check your output. Over the next sunny day, your monitoring app should show production tick back up.

What actually voids the warranty?

Module warranties are more specific than "don't damage it", and the exclusions catch people out.

• Walking on the panels. This is the big one. Standing on a module flexes the cells and creates microcracks — invisible fractures that permanently reduce output and are generally excluded from coverage. There's no safe way to do it, and it's the single most common way a DIY cleaning ends badly.
• Pressure washing. Forcing water past the edge seals is a classic exclusion, and the damage often shows up months later as moisture ingress rather than immediately.
• Abrasives and unapproved chemicals. Scratches scatter light permanently, and solvents can attack the anti-reflective coating and the frame seals.
• Thermal shock. Cold water on hot glass, or hot water on cold glass. Both are avoidable by cleaning early in the morning.

Some manufacturers also specify approved cleaning methods in the installation manual. If yours does, that document is what a warranty claim will be judged against — worth a two-minute read before you buy a brush.

How do you know the cleaning worked?

Measure it, rather than assuming. The method:

1. Note production on a clear day before cleaning, at a specific time of day.
2. Clean.
3. Compare against the same time of day on a similarly clear day afterwards.

Comparing across different weather or different times is meaningless — irradiance moves output far more than dirt does. If you have panel-level monitoring, it's easier still: a single underperforming module against its neighbours usually means one panel is soiled, shaded or faulty, and cleaning tells you which.

The useful negative result: if output doesn't recover after cleaning, soiling wasn't the problem. That points you at shading, a failed optimizer or inverter, or a fault — see why is my solar production low.

What about snow?

Different problem, and mostly one to leave alone.

Panels are dark glass tilted toward the sun. Once light reaches them they warm, the bottom layer of snow releases, and the sheet slides off — often all at once. On a normal pitched roof this usually resolves itself within a day or two of clear weather.

What not to do:

• Don't climb up to clear it. Snow-covered panels on a roof are as dangerous a surface as exists on a house, and you'd be walking on modules to reach them.
• Don't use a metal or hard-edged tool. The scratch risk is the same as any other abrasive.
• Never use salt or deicer. It's corrosive to the frames, the seals and the roof flashing.
• Never use hot water. Cold glass plus hot water is thermal shock.

If you must, a soft-bladed snow rake used from the ground on a low-slope array is the only reasonable option — and even then, accept leaving a thin layer rather than pressing to the glass. Bear in mind that a sliding snow sheet can be heavy and lands where people walk.

Seasonal loss to snow is genuinely small in most climates because the darkest, shortest days produce little anyway. See do solar panels work in winter.

What about birds and animals under the array?

An overlooked maintenance item that costs more output than dust does in many homes.

The gap between the modules and the roof is sheltered, warm and exactly the right size for pigeons and squirrels. Two problems follow: droppings on the glass above, and nesting material packed under the panels, which blocks the rear ventilation the modules rely on to shed heat. Hotter cells produce less — see solar panel temperature and heat loss.

The standard fix is critter guard — a mesh clipped around the array perimeter to the module frames. It's inexpensive, it's usually retrofittable, and it's much cheaper than repeatedly cleaning droppings off glass you can't safely reach.

Have it installed by someone who won't walk on the modules to do it.

When to call a professional

Hire a pro if your roof is steep or high, your array is large, the panels are badly soiled, or there's any sign of damaged wiring or cracked glass. Many solar installers and window-cleaning companies offer panel cleaning, and it's far cheaper than an injury or a cracked module. Ground-mounted and low-slope arrays, on the other hand, are easy to do yourself.

The bottom line

Most solar panels are self-cleaning enough that rain handles them. Clean only when they're genuinely dirty and your output has dropped — and when you do, use soft tools, plain water, cool panels, and no pressure washer. That keeps the glass (and your warranty) intact while you claw back the few percent of production that dirt was costing you. To see how much that lost output is worth, run the solar output calculator, and check the rest of our solar guides.