Can You Pressure Wash Solar Panels? 7 Mistakes That Void Warranties

Q: Can I use a pressure washer to clean my solar panels?

No. Most manufacturers (like LG, Jinko, and REC) explicitly forbid high-pressure cleaning in their warranty manuals. Using a pressure washer can breach the IP65 seals of the junction box, cause water ingress, and create invisible micro-cracks in the silicon cells.

Q: Can I use Windex or vinegar on solar panels?

It is not recommended. Windex contains ammonia, which can strip the delicate Anti-Reflective Coating (ARC) on the glass. Vinegar is acidic and can corrode the aluminum frame and grounding clips over time. The safest cleaner is de-ionized water or a specific pH-neutral solar detergent.

Q: What happens if I wash solar panels on a hot day?

Washing hot panels with cold water causes thermal shock . The rapid temperature difference (often >60°C) can cause the tempered glass to shatter instantly or develop micro-cracks that permanently reduce the panel's energy output. Always clean in the early morning or late evening.

Table of Contents

Thinking of Grabbing the Karcher? Stop.

If you are standing in your driveway right now, staring up at your roof with a 2,500 PSI pressure washer in one hand and a bottle of Windex in the other, put them down. You are about to make a mistake that could cost you upwards of $10,000.

I am a Solar Technical Engineer based here in Australia. I spend my days inspecting residential and commercial PV systems that have failed, underperformed, or simply died on the roof. I have seen systems destroyed by hail, fried by lightning, and eaten by cockatoos. But the most frustrating failures I see aren’t acts of God. They are acts of enthusiastic, well-meaning homeowners who treat their precision electrical equipment like a dirty driveway.

You want to clean your panels. That is a good instinct. Dirty panels lose efficiency. A layer of dust, bird droppings, or that sticky eucalyptus sap we all know and love can drop your system’s output by 5% to 30% depending on the severity and the location.¹ You want to protect your investment. You want to see those kilowatt-hour numbers climb on your inverter app. But by blasting your delicate photovoltaic array with a high-pressure jet, you are not maintaining it; you are assaulting it.

The question “Can you pressure wash solar panels?” has a very short, very blunt answer: No.

The longer answer involves fluid dynamics, the chemical sensitivity of anti-reflective glass coatings, the thermodynamics of tempered glass under thermal load, and the strict, unforgiving legal text found in the fine print of your manufacturer’s warranty. This guide is that long answer. It is a comprehensive, myth-busting report designed to save you from the solar panel cleaning mistakes that will void solar warranty protections and leave you with a rooftop full of expensive, inert glass.

In this guide, we are going to dismantle the seven most common ways DIY cleaners destroy their systems. We will look at the engineering ratings of your junction boxes, the chemistry of your glass, and the strict 2025 safety standards that govern working at heights in Australia. We will treat your solar array not as a slab of indestructible roof tile, but as what it actually is: a sophisticated, fragile piece of electronic power generation equipment that happens to live outside.

The Australian Solar Context: A High-Stakes Game

Australia leads the world in rooftop solar uptake. We have gigawatts of capacity sitting on suburban roofs from Brisbane to Perth. But as our fleet of solar systems ages, the issue of maintenance is becoming critical. Early adopters are now seeing efficiency drops. The “set and forget” mentality is fading, replaced by a desire to clean and optimize.

However, the equipment on your roof today is not the same as the equipment from 2010. Modern panels are larger, the glass is thinner, the coatings are more advanced, and the cell technologies (like PERC and N-type) are more sensitive to micro-damage. A mistake that might have been survivable on an old polycrystalline panel can be fatal to a modern high-efficiency monocrystalline module.³

Furthermore, the Australian consumer law and manufacturer warranty landscape has tightened. Manufacturers are looking for reasons to deny claims. They have forensic teams that can tell if a panel failed due to a manufacturing defect or because someone blasted water into the junction box at 2,000 PSI. If you provide them with that evidence, you are essentially tearing up your warranty contract.

Let’s look at the specific mistakes that will land you in that position.

Mistake #1: The Pressure Washer (The Warranty Killer)

This is the big one. It is the most common error, the most logical-seeming error, and the most catastrophic. The logic seems sound to the uninitiated: “My car is dirty, I pressure wash it. My driveway is dirty, I pressure wash it. My solar panels are dirty, surely I should pressure wash them to get that baked-on bat poop off?”

This logic fails because solar panels are not driveways. They are laminates of glass, silicon, EVA (Ethylene Vinyl Acetate), and polymer backsheets, held together by chemical adhesives and surrounded by sensitive rubber seals. They are designed to shed rain, which falls at terminal velocity (low pressure). They are not designed to withstand a focused jet of water moving at supersonic speeds from a nozzle two inches away.

The Physics of Water Ingress and IP Ratings

To understand why a pressure wash solar panels attempt is disastrous, you must understand the Ingress Protection (IP) rating system. You will see these numbers on the datasheet of every solar panel: IP65, IP67, or IP68.

Every solar panel has a Junction Box (J-Box) on the back. This is where the bypass diodes live and where the cables connect to the panel. The J-Box is the heart of the panel’s electrical safety. It prevents the high-voltage DC electricity generated by the cells from arcing to the frame or the roof.

Let’s break down what those IP numbers mean technically, and why your pressure washer violates their engineering limits.

IP65: The ‘6’ stands for dust tightness. The ‘5’ stands for protection against “low-pressure water jets” from any direction.⁴ The testing standard for IP65 involves a 6.3mm nozzle spraying 12.5 liters per minute at a pressure of roughly 30 kPa (4.3 PSI) at a distance of 3 meters.⁵
IP67: The ‘7’ stands for protection against immersion in water up to 1 meter for 30 minutes.⁶ It does not imply protection against high-pressure jets.
IP68: The ‘8’ indicates protection against continuous immersion under conditions specified by the manufacturer.⁷ It creates a hermetic seal against standing water.

Now, let’s look at your pressure washer.

Your standard domestic pressure washer (like a Karcher, Gerni, or Ryobi) operates between 1,500 and 2,800 PSI. Even a “weak” battery-powered unit outputs 600-1,000 PSI.1

Do the math. An IP65 seal is rated for roughly 4.3 PSI of dynamic water pressure. Your pressure washer delivers 1,500+ PSI.

You are subjecting the rubber gaskets, silicone sealants, and cable glands of your solar panel to a force 300 to 500 times higher than they were engineered to withstand. It is the equivalent of taking a submarine designed for 100 meters depth and dragging it down to the bottom of the Mariana Trench. The seals will fail. It is not a matter of if; it is a matter of when.

The Mechanism of Failure: How the Seal Blows

When you hit a solar panel with 2,000 PSI, particularly around the edges or the junction box, two distinct failure modes occur:

Elastomer Deformation (Seal Blowout): The seals on a J-Box or the frame are made of elastomers like EPDM or silicone. These materials are elastic; they compress to create a seal. However, like any material, they have a limit. The high-velocity water stream exerts a dynamic pressure that exceeds the compressive modulus of the seal. The rubber deforms, momentarily lifting away from the mating surface. In that split second, a gap opens.
Hydraulic Injection: Water is forced through that gap at high speed. It enters the laminate structure or the J-Box housing.¹

Once water is inside the panel, the game is over. It does not simply dry out. It gets trapped.

In the Laminate (Edge Delamination): If water is forced between the glass and the aluminum frame, it can wick into the laminate layers. This moisture reacts with the EVA encapsulant (the glue holding the cells). Hydrolysis occurs, creating acetic acid. This acid then corrodes the silver fingers on the solar cells and the transparent conductive oxide (TCO) layers.¹⁰ You will see this years later as a milky discoloration creeping in from the edges of your panels.
In the Junction Box: Water pools in the J-Box. It bridges the positive and negative terminals.

Corrosion: The copper connections corrode, increasing resistance and heat.¹⁰
Arc Faults: Water conducts electricity. In a high-voltage DC system (up to 600V or 1000V), moisture can create a short circuit. A DC arc is hot—hot enough to melt plastic and start a roof fire.¹¹
ISO Faults: Your inverter constantly monitors the insulation resistance of the DC lines. When water gets in, that resistance drops. The inverter detects a ground fault and shuts down to prevent you from getting electrocuted. You wake up to a red light on your inverter and a system generating zero power.¹²

The Manufacturer’s Verdict: Read the Fine Print

You do not have to take my word for it. The manufacturers are explicitly, legally clear on this subject. Using high-pressure cleaning equipment is an automatic warranty voiding event for almost every major brand sold in Australia.

LG Solar: LG was a premium player in the market (and their warranties are still active). Their cleaning guide explicitly states: “Avoid using high-pressure water, as it can damage the panels or the wiring underneath.”.¹³ Their warranty document excludes damage resulting from “improper maintenance”.¹⁵ If you pressure wash, you have performed improper maintenance.
Jinko Solar: One of the most common brands in Australia. Their manual is precise: “If using pressurized water… pressure do not exceed 3500 kPa (35 bar)… nozzle distance at least 0.5 meters.”.¹⁷ However, they strongly recommend “Wet Manual Cleaning” and warn that high pressure can force water past IP68 junction boxes.³ Note the limit: 500 PSI. Most domestic pressure washers start at 1,500 PSI. You cannot buy a standard pressure washer weak enough to be compliant with Jinko’s warranty.
REC Solar: A premium European brand. They are blunt: “The use of high pressure hoses for cleaning is not permitted… and will invalidate the warranty.”.¹⁸ They cite the risk of frame bonding damage and forcing water between the glass and frame. There is no ambiguity here.
Trina Solar: Another massive player. “Pressurised power washers should not be used directly on the laminates.”.¹⁹ They explicitly list “Avoid jet washing/high pressure cleaning” in their O&M manuals.²⁰
SunPower (Maxeon): Known for the highest quality panels. Their stance? “DO NOT use a pressure sprayer to wet the modules… High-pressure water can damage the solar cells.”.²¹ “Never use a high pressure cleaner. You will also retain the manufacturer’s warranty as a result of this measure.”.²²
Canadian Solar: “Canadian Solar recommends a maximum water pressure of 4 MPa (40 bar)… Damages induced by inappropriate cleaning procedures will void Canadian Solar warranty.”.²³ Again, while they give a higher limit (40 bar is ~580 PSI), your average Karcher K3 produces 1,800 PSI. You are still 3x over the limit.

The Takeaway: If a technician inspects your failed system and sees the tell-tale signs of pressure washing—shredded sealant, clean patches on the frame where oxidation was blasted away, or water marks inside the J-Box—your 25-year warranty is void. You are on the hook for the full replacement cost.

Mistake #2: Thermal Shock (The Glass Breaker)

It is a scorching Australian summer day in January. The ambient temperature is 38°C. You decide it’s the perfect time to cool down the house and clean the panels. You grab the hose (or worse, the pressure washer) and spray cold tap water onto the roof.

You might hear a sound like a pistol shot. Or maybe just a series of sickening crackling pops. You have just destroyed the structural integrity of your solar array through thermal shock.

The Physics of Thermal Stress

Solar panels are dark objects. They are designed to absorb light. This means they get hot—significantly hotter than the ambient air. On a 35°C day, the surface temperature of a solar panel can easily reach 65°C to 85°C.³

Groundwater or tap water usually comes out of the pipe at around 15°C to 20°C. In winter, it can be even colder.

When you hit an 85°C glass sheet with 15°C water, you create a sudden temperature differential ($\Delta T$) of 70°C.

Tempered glass is strong, but it is brittle. It has a specific Coefficient of Thermal Expansion. When the water hits the hot glass, the area in contact contracts instantly. The surrounding glass, still hot, remains expanded. This creates immense tensile stress at the boundary between the wet and dry zones.²⁵

We can model this stress using the equation:

$$\sigma = \frac{E \cdot \alpha \cdot \Delta T}{1 – \nu}$$

Where:

$\sigma$ is the thermal stress.
$E$ is Young’s Modulus of glass (stiffness).
$\alpha$ is the Coefficient of Thermal Expansion.
$\Delta T$ is the temperature difference.

While pristine tempered glass can withstand significant stress, solar glass sitting on a roof is rarely pristine. It has micro-abrasions from dust, tiny chips from hail, and stress risers from the manufacturing process.

Fracture Mechanics: If the tensile stress generated by the cold water exceeds the tensile strength of the glass at any flaw point, the glass shatters. In tempered glass, this results in the entire sheet crumbling into small cubes.²⁶ This is catastrophic failure. The panel is dead.
Micro-cracks in Silicon: Even if the glass doesn’t shatter catastrophically, the silicon cells underneath are even more fragile. Silicon cells are less than 0.2mm thick. The rapid contraction of the glass and the aluminum frame compresses the silicon wafers. This causes “micro-cracks”—tiny fissures in the cell that are invisible to the naked eye but sever the electrical pathways.³

The 20°C Rule

Manufacturers are acutely aware of this phenomenon.

Tongwei Solar, a major cell manufacturer, has released research indicating that a temperature delta >20°C creates a high risk of damage. Spraying 15°C water on a 75°C module (Delta 60°C) carries a “12% chance of immediate microcracks“.³
Jinko Solar: “Do not clean the module when the surface is hot… The temperature difference between water and module cannot exceed 10°C.”.¹⁷
REC Solar: “Cleaning of panels should only be carried out when the panels are cool to avoid thermal shock… early morning.”.¹⁸

The Takeaway: Never, ever clean solar panels in the middle of the day. The only safe times are early morning (before the sun heats the array) or late evening (after they have cooled). A good rule of thumb used by pros: If you can’t touch the panel with the back of your hand comfortably for 10 seconds, it is too hot to wash.

Mistake #3: Chemical Burns (The Efficiency Thief)

In the DIY spirit, many homeowners turn to pantry staples or garage chemicals to clean their panels. “Vinegar cleans windows,” they think. “Windex makes glass shine.” “Dish soap cuts grease.”

Solar panel glass is not window glass. It is high-transmission, low-iron tempered glass, almost always treated with a specialized Anti-Reflective Coating (ARC). This coating is nanoscopically thin and porous, designed to trap light and direct it into the cell. It is extremely sensitive to pH extremes.

The Problem with Windex (Ammonia)

Windex and many standard glass cleaners rely on Ammonia. Ammonia is alkaline (high pH).

ARC Stripping: Harsh alkalis attack the porous silica network of the Anti-Reflective Coating. The chemical reaction ($SiO_2 + 2NaOH \rightarrow Na_2SiO_3 + H_2O$) essentially dissolves the coating.
Etching: Over time, this causes the ARC to cloud over or strip away entirely. Once the ARC is damaged, the glass reflects more sunlight rather than absorbing it. This directly lowers the amperage the panel can produce.²⁸
Voiding Warranty: Most manuals explicitly forbid “harsh chemicals,” “alkali,” “strong acid,” or “industrial alcohol.”.²² Using Windex is a breach of these conditions.

The Problem with Vinegar (Acetic Acid)

Vinegar is a popular “natural” cleaner. It is dilute acetic acid.

Frame Corrosion: While weak vinegar might not instantly destroy the glass, it is acidic. It attacks the anodized aluminum frame and the stainless steel grounding clips. Over time, it promotes oxidation and galvanic corrosion between dissimilar metals.³¹
Warranty Risks: While some DIY blogs suggest dilute vinegar is acceptable for hard water spots ³¹, manufacturers like Jinko list “strong acidic” agents as prohibited.¹⁷ Why risk your warranty on a definition of “strong”?

The Problem with Dish Soap

Dish soap (like Morning Fresh or Palmolive) seems safe. It is roughly pH neutral. The problem here is not corrosion; it is residue.

The Soap Film: Dish soaps contain surfactants and perfumes. Unless you rinse with absolute perfection (which is hard to do with a garden hose on a slanted roof), dish soap leaves a microscopic sticky film.
The Dirt Magnet: This film changes the surface energy of the glass. It becomes sticky. It attracts dust, pollen, and diesel particulates. Within a week, your “clean” panels will be dirtier than they were before you washed them. The sticky residue bonds with dirt to create a grime layer that is harder to remove than the original dust.³²

The Takeaway: Avoid the pantry. If you must use a surfactant, use a specialized solar cleaning fluid (which is low-residue and pH balanced) or a tiny amount of mild, pH-neutral soap, and rinse until you are certain no residue remains. But as we will see in Mistake #4, rinsing with tap water introduces its own nightmare.

Mistake #4: The ‘Garden Hose’ Trap (Hard Water Cement)

You decide to be safe. No pressure washer. No Windex. Just a gentle hose down with tap water.

In many parts of Australia, this is a slow-motion disaster. Australian tap water, particularly in regional areas (like Adelaide, parts of Queensland, and WA), is “hard.” It contains high levels of dissolved minerals, specifically Calcium (Ca) and Magnesium (Mg).

Chemistry of Hard Water Deposits

When you spray hard water on a panel and let it air dry (which you almost always do on a roof), the water evaporates. The minerals do not. They precipitate out of solution and remain on the glass.

Calcium Carbonate ($CaCO_3$): This is limescale. It forms the familiar white spots on the glass. These spots shade the cells. Unlike dust, rain does not wash them off. They are chemically bonded to the surface.³³
Silica ($SiO_2$): This is the real enemy. Silica scale is extremely difficult to remove. Unlike calcium, which can be dissolved with mild acids, silica bonds covalently with the glass (which is also silica). It essentially becomes part of the glass surface through a process called epitaxial growth.³⁴

The “Etching” Effect

If these mineral deposits are left to bake in the sun, they undergo a process called etching. The alkaline minerals react with the glass surface, physically pitting it. This is permanent physical damage.

Shading & Hot Spots: These mineral spots create permanent shading. In a PV cell, shading causes resistance. Resistance generates heat. This leads to “Hot Spots“—localized areas of the panel that overheat. A severe hot spot can burn through the backsheet, melt the encapsulant, or even shatter the glass.⁹
Removal Difficulty: Removing silica scale is a nightmare. It often requires harsh hydrofluoric acid-based cleaners (which are dangerous and void warranties) or mechanical polishing (which destroys the ARC).³⁶

The Takeaway: Do not spray tap water on hot panels and let it dry. If your water is hard (TDS > 100ppm), you are essentially spraying liquid rock onto your energy generator.

Mistake #5: Physical Damage (The Walking Dead)

This mistake is born of convenience. “I can’t reach that middle panel,” you think. “I’ll just step on the edge of this one to reach it. It feels solid.”

The Myth of Walkable Panels

You might have seen marketing photos of people walking on panels. You might know that panels are rated for “snow load” (often 5400 Pascals). This creates a false sense of security.

Distributed vs. Point Load: A snow load is a distributed load. The weight is spread evenly across the entire face of the panel (1.7 square meters). A human foot is a point load. It concentrates 80kg+ into an area the size of a boot heel.
Flexing: When you step on a panel, the glass flexes. It might not break. Tempered glass is flexible. But the silicon cells underneath are brittle wafers. They are ceramics. They do not flex; they crack.³⁷

Micro-Cracks: The Invisible Killer

Walking on panels causes micro-cracks. You cannot see them. The panel looks perfect. But if we were to take an Electroluminescence (EL) image (an X-ray for solar panels), the cells under your footprints would look like shattered windshields.

Degradation: These cracks sever the microscopic fingers that collect electricity. Over time, thermal cycling (expansion/contraction day and night) causes these cracks to widen. Parts of the cell become electrically isolated (dead zones). The panel’s output drops significantly.³⁸
Warranty: Walking on panels is universally excluded from warranties. If a manufacturer tests a returned panel and finds the characteristic spider-web fracture patterns of foot traffic, your claim is denied.³⁹

The Takeaway: Never, ever walk on a solar panel. Not on the frame, not on the glass. If you cannot reach a panel from a safe vantage point or with an extension pole, you need professional equipment or scaffolding.

Mistake #6: Abrasive Scrubbing (The Sandpaper Effect)

Using the wrong brush is a classic rookie error. Using a broom, a stiff floor scrubbing brush, or a scouring pad (like Scotch-Brite) is disastrous.

Scratching the ARC: We mentioned the Anti-Reflective Coating earlier. It is soft. Abrasive bristles scratch this coating off.
Scratching the Glass: Even worse, stiff bristles can micro-scratch the glass itself.

The Tribology of Cleaning: When you scrub a dirty panel, you are moving dust particles across the surface. Dust contains silica (sand). Sand is harder than glass. If you use a heavy hand and a stiff brush, you are essentially sandpapering your panels with the dirt you are trying to remove.
The Result: Scratched glass catches more dirt. It becomes “sticky” to grime. It also scatters light (diffuse reflection) rather than transmitting it, reducing efficiency.¹²

The “Self-Cleaning” Myth:

Some people believe panels are fully self-cleaning. While rain helps, it does not remove bird droppings, lichen, or sticky pollen. Agitation is needed, but it must be soft agitation using a brush specifically designed for the task.

Mistake #7: Ignoring Safety (The Gravity Factor)

This mistake doesn’t void your warranty; it voids your life insurance.

2025 Australian Safety Standards

In 2025, the regulations surrounding “Working at Heights” in Australia are stricter than ever.

The 2-Meter Rule: Under the Model Work Health and Safety Regulations, if there is a risk of falling more than 2 meters (which is almost every roof in Australia), you must have fall protection controls in place.⁴⁰
The Hierarchy of Control: The standards prioritize working from the ground. If you can clean your panels from the ground using an extension pole, you are legally and morally obligated to do so. If you must get on the roof, you need a harness, anchor points, and training.
Ladder Safety: Falls from ladders are a leading cause of injury and death in Australian DIY projects. Standing on the top rung, overreaching with a pressure washer wand, and dealing with slippery wet roof tiles is a recipe for disaster.

Insurance Implications

If you fall off your roof while DIY cleaning:

Personal Injury: You are likely not covered by Workers Comp. Income protection insurance often has exclusions for “reckless” behavior or engaging in hazardous activities without proper safety gear.
Property Damage: If you slip and put your foot through a ceiling tile, or drop the pressure washer through the roof, your Home and Contents insurance may deny the claim. Many policies have exclusions for “illegal acts” (violating WHS laws regarding heights) or damage caused by “poor workmanship” or lack of maintenance skills.⁴²
Liability: If you drop a brush and it hits a neighbor or their car, you are liable.

The ‘Right’ Way: How to Clean Without Destruction

So, how do you clean them? If pressure washers, tap water, and Windex are out, what is left?

The professional industry standard is simple, elegant, and safe. It relies on physics and chemistry rather than brute force.

1. The Equipment: Soft Bristles & Extension Poles

Use a water-fed pole. This is a long, extendable carbon-fiber or aluminum pole with a specialized brush head.

The Brush: It must use soft, flagged bristles (monofilament). “Flagged” means the tips of the bristles are split into tiny hairs. This makes them incredibly soft and able to lift dirt without scratching.⁴⁴
The Pole: Allows you to clean from the ground or the gutter line, eliminating the need to walk on the roof.

2. The Agent: De-ionized (DI) Water

This is the secret weapon. Professionals do not use tap water. They use De-ionized water.

What is it? Water that has passed through a DI resin filter vessel. The resin beads attract and trap dissolved mineral ions (Calcium, Magnesium, etc.), swapping them for Hydrogen and Hydroxyl ions, which form pure water. Ideally, the water has a TDS (Total Dissolved Solids) of 0 ppm (parts per million).⁴⁵
The “Hungry” Water: Because DI water has no ions, it is chemically “hungry.” It aggressively bonds with dirt and minerals on the panel, pulling them off the glass. It acts as a solvent without needing soap.
Spot-Free Rinse: Because there are no minerals in the water, you do not need to squeegee it dry. You can let it air dry, and it will leave zero spots. No calcium, no silica, no shading.⁴⁵

Comparison Table: High Pressure vs. Soft Wash

Feature	High Pressure Wash (DIY)	Soft Wash (Professional/DI Water)
Pressure	1,500 – 3,000 PSI	< 60 PSI (Garden Hose Pressure)
Water Type	Tap Water (High Mineral Content)	De-ionized Water (0 ppm Minerals)
Tool	High-velocity jet nozzle	Soft-bristle flagged brush agitation
Risk to Seals	EXTREME (Water Ingress)	LOW (Safe for IP65/67)
Risk to Glass	HIGH (Thermal Shock/Fracture)	LOW (Ambient Temp Water)
Result	Clean but damaged seals; hard water spots	Spot-free; intact coatings; safe seals
Warranty	VOID	MAINTAINED
Cost	Free (until replacement needed)	$150 – $300 (Professional Service)

Conclusion: Protect Your Warranty, Protect Your System

Solar panels are robust, but they are not invincible. They are designed to withstand hail, wind, and rain—not 2,000 PSI point-blank water jets, chemical baths, or the weight of a boot.

When you pressure wash your panels, you are essentially gambling 25 years of free electricity against 30 minutes of cleaning time. It is a bad bet. The manufacturers—LG, SunPower, Jinko, Trina—have all drawn a line in the sand. Cross it, and you are on your own.

My final advice as an engineer:

Throw away the pressure washer idea. It is never worth the risk.
Buy a proper kit. If you are dead set on DIY, invest $200-$400 in a water-fed pole with a DI resin filter attachment. It connects to your garden hose and makes safe water.
Or, hire a pro. For roughly $10-15 per panel, a professional with the right gear will do it safely, better, and without voiding your warranty.

Don’t let a “clean” system become a dead system.

Can I use a pressure washer to clean my solar panels?