Clean solar panels make more electricity—full stop. Different factors such as dust, pollen, bird droppings, salt from coastal regions, ash from wildfires, and overspray from sprinklers can create a film that makes less light to your modules into electricity. For many homes, rainfall keeps panels reasonably clear. With a routine clean-up, the remaining area can also generate a meaningful output for others. This guide tells you when and how to clean them safely, which tools to use, which mistakes to avoid and more importantly, how to know you are worth the effort.
Safety first. Working at height is risky. If your roof has a steep slope, slippery surface, or high elevation that makes it unsafe, do not attempt to go up on it. Instead, use a long water-fed pole from the ground or hire a professional to do the job. When required, always employ stable ladders, non-slip shoes and fall protections. Never step on panels.
Electricity awareness. Panels generate power whenever they see light. Sealed electrical equipment shouldn't be opened, wired disconnected or sprayed with water. Keep connectors dry and intact.
Warranty check. Some manufacturers tell you what not to do (e.g., don’t use abrasive pads, harsh chemicals, pressure washers). Using prohibited methods can void warranties. If in doubt, follow the module maker’s care instructions.
Pick the right moment. A cool, cloudy day in the early morning or late evening. If you clean hot glass with cool water, it results in thermal shock and may cause micro-cracking or warping. The low sun gives less risk of generation while you work and less streaks as water evaporates slowly.
Most panels only need water. If grime is oily or sticky, use one of these gentle mixes.
Add a little dish soap to every gallon or liter of water.
To clean off the film of mineral deposits use white vinegar to water.
Don’t use ammonia, bleach, solvents abrasive powders, or anything “heavy duty.”
Do you actually need to clean? A quick decision check.
Look from the ground. Are there visible droppings, pollen trails, ash, or dust haze?
Check performance. You should compare your current output to months with similar weather and to nearby arrays (many monitoring apps have a performance vs expected view).
Consider environment and tilt. Areas with low-tilt arrays like below 10-15 degrees, dusty areas and areas near the trees often get neglected. Steeper roofs and rainy climates may need far less.
If you don’t see heavy soiling and production looks normal for the season, you can likely wait. Cleaning too much can waste as much as cleaning too little.
Power-down area, not the system. Unless your installer directs you otherwise for servicing, do not turn off your solar. Instead, make the work area safe by securing the ladder, cordoning off the ground below, and wearing gloves and eye protection.
Dry debris removal (optional). If it is safe, hold a leaf blower two inches away from the ground and blow off dust (not soil). This reduces smearing later.
Pre-rinse. Lightly rinse panels to float off grit. Use the gentlest spray pattern. Do not spray water under panel frames and roof penetrations.
Apply cleaning solution. Gently brush or rub the glass with the solution. You can use a soft brush or microfiber pad for this.step. To remove film from glass, you want to think “dusting.” Circular or long overlapping strokes both work. Your goal is to loosen the film, not polish the glass.
Dwell briefly, then rinse. Allow the solution to soften stubborn spots for 30 to 60 seconds before scrubbing. Rinse thoroughly with DI/distilled water if you have it. If you are using tap water, thoroughly rinse and continue with the next step right away.
Squeegee to finish. Using your rubber blade, draw a clean swipe from top to bottom (or side to side if safer), overlapping each swipe to avoid streaks. Wipe the blade with a microfiber cloth between pulls.
Spot cleanup. To clean off any baked-on droppings or sap, cover the area with a wet microfibre cloth for a minute to soften it. Then, use the cloth or the very edge of a plastic scraper wrapped in microfibre. Don’t use metal, steel wool, melamine sponges or gritty pads
Final check. Inspect from the ground. If you spot a milky sheen, it means there is something leftover. In most cases, a quick rinse and squeegee will clear away the residue.
Hard water. Water with minerals causes spots as the light scatters. Wipe it down really well before the drops dry, or do a final rinse with DI.
Wildfire ash and soot. Ash can be mildly alkaline and clingy. Use a generous spray of water, soap solution, and rinse carefully. The first rinse will probably go grey. Continue rinsing until the rinse water is clear.
Bird droppings. These can cause “hot spots” by shading cells. If you want to treat an area between the full cleanings, a squeeze bottle of DI water and a microfiber pad on a pole is great solution.
Pollen season. Pollen often forms a waxy film when mixed with dew. A little vinegar in your water helps cut it. Plan a post-season clean for best results.
Coastal salt. Salt spray can leave conductive residue and dull the glass. Once a quarter cleaning if you are near the coast and feel free to DI rinse.
Snow and ice. Don’t pour hot water on cold glass. If you must, use a soft foam snow rake designed for solar. Oftentimes, when the sun and the panel heat the snow, it clears relatively quickly once the surface warms up. After things begin to melt, what’s most important is cleanliness.
There is no one answer, but it changes with where, when and what strikes your roof. As a starting point.
In places where it rains or the temperature is moderate, once a year, or even ‘as needed.’
Dusty or agricultural areas: Once in 1-3 months in dry seasons.
Coastal zones: Quarterly.
Check under trees and around heavy birds each month; spot-clean droppings.
Low tilt arrays (<10°): Common; water doesn’t shed as well.
Figure it out based on data: record your system’s day kWh each clear day and season. If you notice a consistent decrease (after accounting for temperature and sun angle), it may be time.
Pick a comparable day. Pick a day before cleaning and another day to try the wash, same temperature and clouds.
Log output. To complete this task, you need to extract the midday power (kW) and daily energy (kWh) from your inverter/app. If you see “Expected” vs. “Actual” on the app, take a screenshot.
Normalize for system size. To monitor kWh/kW, divide kWh by your system’s kW (e.g., 7.2kW), which makes it easier to compare year-over-year.
Look for durable gains. If we only see a bump for a day, it’s more rubbish.
If you only see a slight bump your site may not need cleaning that frequently, or the performance issue lies elsewhere (shading from new growth, inverter/optimizer faults, tripped breaker on a string).
Critter guards and bird deterrents. Mesh guards around the array perimeter keep pigeons from nesting and reduce droppings.
Trim overhanging branches. Less sap, pollen, shade, and leaf litter.
Avoid sprinkler overspray. Re-position irrigation heads to avoid the roof to lessen hard water stains.
Ground cleanliness. If you gravel or clean near the eaves you can reduce a splash-back.
Consider coatings cautiously. There are coatings that are “anti-soiling” or hydrophobic that can create warranty complications and won’t eliminate the necessity for cleaning. Consider cost, any impact on warranty and proven performance over time before applying.
Water use. Be mindful during drought. Often a light rinse plus squeegee is enough. A pole that is fed with water can be useful as it reduces spotting and reworks.
Runoff. Keep harsh chemicals out of storm drains. Use soap at low concentrations or just simple water.
Roof integrity. While you are up there in those places, check for cracked tiles/shingles, loose flashing, as well as signs of nesting. Early fixes prevent leaks and rodent damage.
Personal safety. If the wind picks up or surfaces get slippery, stop. A small output gain isn’t worth a big fall risk.
The water which spot less and rinses better is purer. A usable reference is TDS < 30 mg/L (ideally < 10 mg/L) or equivalent conductivity < 20 μS/cm (ideally < 10 μS/cm) for spot-free drying. If you must use tap water, always follow with a DI rinse or squeegee before the water spots dry. Otherwise, the minerals will bake under the sunlight and etch the glass permanently. This can also affect light transmission.
It is beneficial to lightly brush and low-pressure rinse the rear side of ground-mounts, carports, and other accessible sites. This helps to preserve back-side gains. As rear access is mostly constrained in rooftop systems, forcing brushes in risks damage to cables and junction-boxes. Avoid letting water pool around frame gaps or cable glands. Following the cleaning, also check the ground or reflective surface on which the array is placed. Cleaning or brightening this area may increase back-side yield more than cleaning the rear glass.
Yes. Always choose neutral (pH ~6–8), low-residue formulations. Stay away from strong acids and strong bases, toothpaste with fluoride, ammonia, solvents, or abrasive particles.
Test any new chemical on a small area only, limit the dwell time to not greater than 1 minute and rinse well with clean water (preferably DI). Unless the manufacturer permits it, always use only a diluted solution (≤10-20%) of isopropyl alcohol (IPA) for spot-cleaning of sticky deposits, and never spray it broadly. Do not use solvents around sealants and other parts.
Begin with quantifying soiling losses against annual costs.
Yearly Generation × The Average Rate Of Soiling = Annual Energy Loss in kWh.
The total loss of revenue will depend on the tariff/rate. If the loss in revenues every year is greater than the annualized cost of the cleaning system (depreciation of equipment + maintenance + water/power + labour) then it may be worth investing in equipment. It is considered most valuable in low tilt arrays, dusty/coastal climates or large utility scale plants where labour costs are high.
Keep an eye out for issues such as the buildup of minerals in spray systems, the wearing-down of brushes, and battery maintenance in robots as well as rail systems that can withstand storms and heavy snowfall. The load tolerance of modules and racking should always be confirmed before deploying machines.
If there’s alkaline dust on your surface like cement, lime or ash then firstly pre-soak. After that use a neutral or mildly acidic water lightly with a soft brush. Rinse and squeegee dry.
Oil/asphalt/paint dots may be removed mechanically. If deemed acceptable, no more than spot clean with diluted IPA or citrus cleaner followed by water rinse. Avoid harsh solvents.
To make the impression of moss and lichen, soak them in cool water. Next, use a soft brush, or you can also use a mild biocide that’s approved and then rinse thoroughly.
If the stain doesn't go away or the AR coating appears to be wearing off, stop and call the manufacturer or one of the professional O&M teams.
