How often should you clean solar panels?
Updated July 2026
Rinse residential solar panels every 6 to 12 months, and lean toward twice a year if you live somewhere dusty, pollen-heavy, or dry enough that rain rarely does the job for you. Soiling on the glass blocks light before it reaches the cells, and the array you paid five figures for quietly gives back 5–20% of its output the dirtier it gets. In rainy regions the weather handles most of it; in the desert Southwest and farm country, it does not.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Rainy climate (Pacific NW, Northeast) | Once a year | Regular rain rinses most dust before it builds up |
| Desert Southwest (dust, little rain) | Every 3–6 months | Dust settles and bakes on with no rain to clear it |
| Near farms, dirt roads, or construction | Every 3–6 months | Airborne soil and pollen coat the glass fast |
| Heavy tree cover (pollen, droppings, sap) | Every 6 months | Organic soiling shades cells and can etch the glass |
| Low-tilt or flat-mounted arrays | Every 6 months | Shallow angles let water pool and dirt stay put |
| Steep roof pitch, clean-air suburb | Every 12 months | Rain runoff on a steep slope self-cleans well |
The cost of skipping it
What skipping it costs: a soiled array loses 5–20% of its production, and in dust-belt regions researchers have measured worse. On an 8 kW system that can mean 500–1,500 kWh a year of electricity you paid for but never harvested, roughly $75–300 depending on your rate, every year the film stays. Ground-in droppings and sap can create permanent hot spots that shorten a panel's 25–30 year life. A DIY hose-and-brush cleaning is free; a pro visit runs $150–350.
How to do it (20–40 minutes · DIY from the ground, or $150–350 pro)
- Do it early morning or on a cool, overcast day; cold water on hot glass can crack panels, and you want to work in shade.
- Shut the system down at the inverter or disconnect if your installer recommends it for your equipment.
- Rinse the panels with a plain garden hose to float off loose dust first.
- For stuck-on grime, use a soft brush or squeegee on a pole with a little dish soap or a solar-panel cleaner; never abrasive pads or pressure washers.
- Rinse again with clean water and let the panels air-dry to avoid spotting.
- Check your monitoring app afterward; a jump in production confirms the clean paid off, and flags any panel that stays low.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing solar panel cleanings schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
Can I just let the rain clean my solar panels?
In a wet climate, mostly yes: frequent rain rinses off the loose dust that causes the bulk of soiling losses, which is why annual cleaning is plenty in the Pacific Northwest or Northeast. Rain fails you in two situations: long dry spells, where the Southwest can go months and dust bakes on, and sticky soiling like pollen, tree sap, and bird droppings that water alone will not lift. Those need a hands-on cleaning to recover the lost 5–20% of output.
Is it safe to clean solar panels myself, or should I hire someone?
From the ground with a hose and a soft-bristle pole brush, DIY is safe and free. The moment you would need to be on the roof, hire a pro: wet panels and wet roofing are slick, and a fall outweighs any cleaning benefit. Pro cleanings run $150–350 for a typical home array and often include a quick visual check of the racking and wiring. Never walk on the panels themselves, and never use a pressure washer, which can force water past the seals.
Do dirty solar panels really lower my electric bill savings that much?
Yes, quietly. A film you can barely see can trim 5–10% off output, and heavy soiling in dusty regions has been measured at 20% or more. On a five-figure rooftop system that difference stretches the payback period by months to a couple of years, because every kilowatt-hour the panels miss is one you buy back from the utility at full retail. Cleaning is the cheapest way to protect the return on the biggest home-energy purchase most owners make.