How Often to Clean Solar Panels: A Los Angeles Homeowner's Guide (2026)

Do solar panels need to be cleaned? Yes. Rain cannot remove bird droppings, smog film, pollen, or wildfire ash, and in Los Angeles, panels can go five to seven months without a meaningful rinse. Most LA homes need a professional cleaning one to two times a year, plus an extra visit within days of any wildfire ash event.

That said, the right schedule for your home is not a fixed number. It depends on your panel tilt, your distance from freeways and the coast, the trees and birds around your roof, and how much your monitoring app shows output slipping between cleanings. This guide breaks down what the research actually says about dirty panels, gives you an LA-specific cleaning schedule, and shows you how to calculate whether a cleaning is paying for itself.

How Often Should You Clean Solar Panels?

For most residential systems, the general rule is once or twice a year. National guidance ranges from one to four cleanings a year depending on climate, and homes in dry, dusty, or polluted areas sit at the higher end.

Here is how that translates across Los Angeles:

Coastal homes get some natural rinsing from the marine layer, but salt spray still leaves mineral deposits. Valley and inland homes see less moisture and more dust, so soiling builds faster. Homes beside major freeways collect a greasy particulate film from vehicle exhaust that rain does not lift.

What the Research Says About Dirty Solar Panels

Soiling is the industry term for dust, pollen, soot, droppings, and other material that settles on panel glass and blocks sunlight. It has been studied closely in California for two decades, and the data tells a more nuanced story than most cleaning ads.

Daily soiling rates.

A landmark study of large grid-connected systems across California and the Southwest found that panels lose roughly 0.1% to 0.3% of output per day during dry periods, with an average of about 0.2% per day. Depending on location, annual soiling losses ranged from 1.5% to 6.2%.

The California residential picture.

UC San Diego engineers analyzed 186 residential and commercial sites from the Bay Area to the Mexican border. Over a 145-day summer drought, the average panel lost 7.4% of its efficiency, or about 0.05% per day. For an average, well-tilted home system with ordinary dust, the researchers concluded that a mid-summer wash often would not pay for itself.

Why do the averages hide the real problem?

The same UC San Diego study found that 48 of the 186 sites had much faster soiling, and panels tilted at less than 5 degrees lost about five times more than steeper ones. In other words, the average is skewed by the many systems that stay fairly clean. The homes that need cleaning most are the outliers: flat roofs, low-tilt arrays, homes under trees, and homes near freeways, farms, or construction.

Flat panels can lose far more.

When Google cleaned 1.6 megawatts of nearly horizontal carport panels at its Mountain View campus after 15 months without cleaning, output doubled overnight. A second cleaning eight months later raised output another 36%.

The global cost.

A 2019 study in the journal Joule estimated that soiling cut worldwide solar production by at least 3% to 4% in 2018, costing at least 3 to 5 billion euros in lost revenue, with losses projected to grow as more solar is built in dusty regions.

Wildfire smoke and ash.

During the September 2020 California fires, a National Center for Atmospheric Research study found that smoke cut solar production by 10% to 30% during peak afternoon hours. Smoke clears on its own, but the ash it leaves behind does not.

The takeaway:

Ordinary dust on a well-angled panel causes modest losses. Bird droppings, ash, freeway grime, and flat mounting cause much larger ones. Your cleaning schedule should follow what is actually landing on your panels, not just the calendar.

Why Solar Panels Get Dirtier in Los Angeles

Several local conditions push LA homes toward more frequent cleaning than national averages suggest.

A long dry season.

Downtown Los Angeles averages about 14.25 inches of rain a year, and nearly all of it falls between October and April. From late spring through early fall, nothing rinses the glass, and that dry stretch overlaps with the months your panels produce the most power.

Some of the worst air in the country.

The American Lung Association’s State of the Air report has ranked Los Angeles-Long Beach as the most ozone-polluted metro in the nation in 25 of its 26 years of reporting, and the 2026 report ranked it again for ozone and seventh-worst for year-round particle pollution. That fine particulate settles on panel glass as a thin film that builds week after week.

Santa Ana winds.

Santa Ana wind events carry dust, grit, and ash across the basin for days at a time, sweeping in from inland deserts and burn areas. Panels can lose noticeable output within a day or two as that debris settles, and the dry winds bring no rain to rinse it away.

Wildfire ash.

Ash is alkaline. When morning dew or light rain wets it, the ash bonds to the glass and becomes much harder to remove than ordinary dust. Left for more than a few days, it can begin to damage the anti-reflective coating that helps your panels capture sunlight.

Coastal salt and hard water.

Salt spray in beach communities like Santa Monica, Venice, and Malibu, along with sprinkler overspray and hard tap water inland, leaves calcium, magnesium, and salt deposits that dry onto the glass. Those mineral spots scatter incoming light, bond tighter over time, and resist being washed off by rain alone.

Birds and trees.

Bird droppings are one of the most damaging forms of soiling because they block light completely over one spot. On older panels, that localized shading can create hot spots that stress the cells over time. Pigeons also like to nest under rooftop arrays, and nearby eucalyptus, jacaranda, and pine trees add sap, pollen, and leaf litter.

Does Rain Clean Solar Panels?

Only partly. Rain washes away loose surface dust, but it does not remove bonded grime, droppings, mineral spots, or sap. In one rooftop experiment on low-slope panels, a hand cleaning with water and a soft cloth raised energy output by about 3.5%, while a heavy rainstorm on the same dirty panels raised it by only 1.9%.

Rain also brings its own problems. Rainwater carries dust and pollen, and on low-tilt panels it can pool along the lower frame edge, then evaporate and leave a muddy line behind. In Los Angeles, the bigger issue is simply timing: months of buildup sit on the glass before the first storm arrives, and light early-season showers often turn dry dust into a streaky film instead of washing it away.

Signs Your Solar Panels Need Cleaning Now

You do not have to wait for a scheduled visit if any of these show up:

• Production is down compared with the same month last year on similar sunny days, and your inverter shows no errors.
• Bird droppings or nesting debris are visible on the glass or around the array edges.
• A Santa Ana wind event or nearby wildfire has left ash or grit on cars, patios, and windowsills.
• Construction, roadwork, or demolition is happening nearby.
• Your panels sit nearly flat and you can see a dirt line along the bottom edge.
• Panel-level monitoring (common with microinverters) shows some panels producing noticeably less than others in full sun.

Monitoring is the most reliable test. A sudden drop usually points to equipment issues, while a slow, steady decline across all panels usually points to soiling.

How to Tell Whether Cleaning Pays for Itself

You can estimate what soiling costs you with a simple formula:

Annual solar production (kWh) × soiling loss (%) × your electricity rate ($ per kWh) = yearly cost of dirty panels

Your annual production is listed in your monitoring app or your installer’s original proposal. Southern California Edison residential rates average roughly 34 to 35 cents per kWh in 2026, while LADWP customers pay closer to 22 cents.

Here is a worked example for a typical 7 kW system in Los Angeles producing about 10,500 kWh a year:

A standard residential cleaning in Los Angeles typically costs $120 to $350, depending on system size and roof access. For lightly soiled, well-tilted panels on LADWP rates, one cleaning a year usually makes the most sense. For SCE customers, low-tilt arrays, or homes facing ash, droppings, or freeway grime, two cleanings a year often pay for themselves.

One more factor: under California’s current net billing rules, power you use at home is worth more than power you export to the grid. If your household uses most of its solar production directly, each recovered kWh is worth closer to your full retail rate.

The Best Time of Year to Clean Solar Panels in Los Angeles

If you clean twice a year, timing matters as much as frequency.

• Late spring (May to June):

  Clean before your highest-production months. Your panels start the long dry season at full output, right when every kWh counts most.

• Early fall (September to October):

  Clear the buildup from the dry season, smog peak, and early Santa Ana events before winter.

• Any time after a wildfire:

  Schedule as soon as conditions are safe. Ash should not sit through dew cycles or a light first rain.

On the day itself, early morning or evening is best. Manufacturers warn against spraying cool water on sun-heated glass because the sudden temperature change can stress the panel, and cleaning a hot panel also causes water to evaporate before it can rinse properly.

How Solar Panels Should Be Cleaned

Panel manufacturers are specific about cleaning because the wrong method can damage the glass and void the warranty.

• Use pure water.

  REC’s cleaning guide names deionized water as the ideal choice, because it carries no dissolved minerals that dry into spots and leave a hazy film across the glass.

• Use soft tools only.

  Manufacturers recommend soft brushes, sponges, or microfiber cloths, and they warn against scrubbing dry dirt off the panel, which can leave micro-scratches across the glass surface.

• Skip pressure washers.

  REC does not permit pressure washers, steam cleaners, or high-pressure hoses on its panels and says they invalidate the warranty, while Trina Solar voids coverage for inappropriate cleaning damage.

• Avoid harsh chemicals.

  Ammonia, abrasive cleaners, and solvents can damage the anti-reflective coating on the glass and leave behind a residue that attracts new dirt faster after cleaning.

• Never walk on the panels.

  Standing, kneeling, or leaning on modules, or resting tools and buckets on them, can crack the cells underneath in ways you cannot see from the surface.

Our solar panel cleaning service follows these guidelines: water filtered through sediment, carbon, reverse osmosis, and deionization stages down to 0 TDS, soft-bristle brushes on a water-fed pole, zero pressure, and zero chemicals.

DIY or Professional Cleaning?

Ground-mounted panels that you can reach safely from the ground are a reasonable DIY job with a garden hose, a soft brush, and filtered water. Rooftop arrays are a different story. Ladder work, sloped and tile roofs, and wet glass create real fall risk, and stepping on the array or using the wrong tools can cause more damage than any amount of dust.

A professional visit also adds an inspection. Technicians can spot cracked glass, loose mounting hardware, nesting birds, or chewed wiring before those problems cost you production. If you lease your system, check your agreement first, since some leases include periodic cleaning or specify who must do it.

Solar Panel Cleaning Costs in Los Angeles

The easiest way to stay on schedule is a recurring plan. Our six-month memberships schedule two panel cleanings a year with reminders and priority rebooking. Many homeowners also pair panel care with exterior window cleaning because the same smog, dust, and sprinkler spray coats both surfaces, and the Complete Exterior package adds gutter cleaning so the roofline is handled in one visit.

Not sure how often your system needs service? We serve Los Angeles and cities within about 30 miles, and we will recommend a schedule after seeing your panels firsthand. Call (818) 714-4721 or request a complimentary quote with your ZIP code and panel count.

Frequently Asked Questions

How often should solar panels be cleaned in Los Angeles?

Most LA homes need cleaning one to two times a year. Coastal homes can often go once a year, while Valley, inland, and freeway-adjacent homes do better with two cleanings. After any wildfire ash event, clean within days instead of waiting for your next scheduled visit.

What happens if I never clean my solar panels?

Your system keeps working, but output slowly declines as dust, film, and droppings build up. California research shows typical losses of about 0.05% to 0.2% per day during dry periods, and flat or heavily soiled panels can lose far more. Bird droppings left in place can also create hot spots on older panels.

How much power do dirty solar panels lose?

It depends on the type of soiling. Ordinary dust on tilted panels usually costs a few percent per year, while a 145-day California dry spell averaged a 7.4% loss across 186 sites. Flat panels, ash, and droppings can push losses well above 10%.

Is cleaning solar panels worth the money?

It is when soiling losses are higher than the cleaning cost. Multiply your annual production by your estimated loss and your electricity rate. SCE customers, low-tilt systems, and homes facing ash or freeway grime usually come out ahead with regular cleaning.

Can I use a garden hose to clean my solar panels?

A gentle rinse with a regular garden hose is generally acceptable for ground-level panels. Tap water can leave mineral spots, though, which is why manufacturers prefer deionized water. Never use a pressure washer, and avoid climbing onto the roof yourself.

What is the best time of day to clean solar panels?

Early morning or evening, when the glass is cool. Spraying cool water on hot panels can cause thermal stress, and water evaporates too fast on hot glass to rinse properly.

Will cleaning my solar panels void the warranty?

Proper cleaning will not. Manufacturers specifically recommend soft tools and low-pressure, low-mineral water. Pressure washers, steam cleaners, abrasive tools, and harsh chemicals are what can void coverage.

Should I clean my solar panels after a wildfire?

Yes, as soon as it is safe. Wildfire ash is alkaline and bonds to the glass when it gets wet. Cleaning within days helps prevent coating damage and restores lost output quickly.