Solar panel cleaning has a low barrier to entry. A truck, a ladder, and a brush is enough to start advertising, which means quality across Arizona providers varies more than you would expect for a service involving your roof and a live electrical system. What follows are the questions worth asking anyone, ourselves included.
Insurance comes before anything else
Ask about two policies: general liability and workers' compensation. Ask to see the certificate rather than accepting a verbal yes, and check the dates on it.
The reasoning is unglamorous. If someone falls off your roof and the company employing them carries no workers' compensation, that injured person's path to being made whole runs through your homeowner's policy. Property damage works the same way. Cracked roof tiles, a broken panel, water forced into a junction box: liability coverage is what stands between an accident and an argument.
A company that gets uncomfortable with this question has already answered it.
Method and water: ask what touches your glass
How a crew cleans matters more than how long they spend doing it.
- What water do you use? Straight tap water in the valley carries enough dissolved mineral to dry into scale on hot glass. Deionized or purified water dries without spotting, which is why it has become the standard for solar work.
- What is in the water? The answer should be nothing. Detergents leave a film that attracts dust, and some panel warranties name cleaning agents as an exclusion.
- Do you pressure wash? The answer should be no. Pressure can force water past frame seals into wiring and can break the bond between glass and frame.
- What contacts the panel? Soft brushes on water-fed poles. Not scouring pads, not scrapers, not stiff bristles that scratch the anti-reflective coating.
- When do you clean? Early, on cool glass. Cold water on glass that has been baking since sunrise is thermal shock nobody needs.
- Do you walk on the panels? Never acceptable. Foot pressure creates microcracks in cells that surface as output loss years down the line.
Local experience shows up in the details
Arizona conditions are specific, and a crew that has worked here a while will raise them without being prompted.
- They know summer storms deposit dust rather than washing it off, so they schedule around monsoon season instead of assuming the rain did the work.
- They handle tile roofs carefully, because valley tile cracks under careless footing and the leak shows up in July.
- They have an opinion about foam and flat roofs, which mark and puncture differently than shingle.
- They can describe what bird activity looks like here, where pigeons nest year-round rather than seasonally.
- They know shallow-tilt arrays hold soiling far longer than steeply pitched ones, and they price the interval accordingly.
Bird proofing, paperwork, and red flags
If birds are part of your problem, a company that only cleans is selling you a recurring appointment. Ask whether they install exclusion mesh, what it is made from, whether anything gets drilled into panel frames or through the roof, and whether the area gets cleared and cleaned before it is closed up.
On documentation, expect a written scope and price before work starts, before and after photos, and a note describing anything they found up there. That record is what supports a warranty claim later.
Things that should slow you down:
- A specific percentage gain promised before anyone has looked at your array
- Door-to-door pressure and same-day-only pricing
- No written quote, or a price that changes once they are on the roof
- A free inspection that discovers an urgent and expensive problem
- Reluctance to name their water source and method
- Long contracts with cancellation penalties, for a service that should earn the next visit
Most good local companies answer all of this comfortably, because it describes how they already work. Two Bits Solar Cleaning runs deionized water systems and soft water-fed equipment, and installs bird proofing with no roof or frame penetrations. Our services page lays out the specifics, the FAQ covers the questions we hear most, and you are welcome to put these same questions to us before deciding.