Dirty solar panels lose 15–25% of their efficiency, yet many homeowners don't know what questions to ask when hiring a cleaner. A good solar panel cleaning provider should be transparent about methods, insurance, and guarantees—not just quote a price and show up. Here's how to vet providers before signing anything.
What Cleaning Method Do They Use?
This is the first technical question that separates competent providers from amateurs. Ask whether they use deionized water systems, soft brushes, or pure water fed poles. Avoid anyone who suggests high-pressure washing—it can damage panel seals and coating. Most reputable cleaners use pure water fed poles (DI systems) that leave no mineral residue and don't require climbing directly on your roof, which reduces risk.
Ask specifically about their cleaning solution: is it pure water only, or do they add detergents? If they add products, request the safety data sheet to ensure nothing corrosive touches your panels or runs into your soil.
Are They Insured and Licensed?
This question protects you financially if something goes wrong. Request proof of general liability insurance (minimum $1 million coverage) and workers' compensation if they're sending employees onto your roof. Don't accept verbal assurances—ask for a certificate of insurance naming you as an additional insured.
Check whether they're licensed in your state or municipality. Licensing requirements vary widely, but some states now require certifications for solar work. A provider who can't produce documentation is a red flag.
How Often Should I Schedule Cleanings?
There's no one-size-fits-all answer, but the provider should give you realistic guidance based on your location. Dusty, dry climates need more frequent cleanings (every 3–4 months), while rainy regions might only need annual service. Ask them to explain the reasoning—if they automatically recommend monthly cleanings without knowing your environment, they're selling you more service than you need.
Request a seasonal assessment: do leaves, pollen, or bird droppings accumulate on your roof in certain months? A thoughtful provider will tailor a schedule to your actual conditions, not their commission target.
What's Your Pricing Model?
Get a detailed quote that breaks down labor, materials, and travel charges. Solar panel cleaning typically ranges from $150–$400 for residential systems (depending on size, accessibility, and region), though some providers charge per panel or per kWh of system capacity.
Ask these specifics:
- Do prices change if panels are angled steeply or hard to access?
- Is there a travel fee if you're outside their service area?
- Do they offer package discounts for quarterly or annual contracts?
- What happens if they damage a panel during cleaning—do they cover repairs?
Compare at least three quotes. If one is drastically lower, ask why. They may be cutting corners on insurance, water quality, or equipment.
Do You Offer Performance Guarantees?
A solid provider should guarantee their work for a set period. Ask: if efficiency doesn't improve after cleaning, will they return for free? How do they measure improvement—visual inspection, or actual energy output data? Some will even monitor your system's production before and after cleaning using your inverter data.
Clarify the timeframe. A typical guarantee covers 30–90 days of service, accounting for weather and normal dust accumulation.
What's Your Cancellation and Rescheduling Policy?
Ask about flexibility before you book. What happens if weather forces postponement? Can you reschedule with 24 hours' notice without penalty? If there's a cancellation fee, it should be reasonable (typically no more than 10–15% of the quoted price).
Some providers offer seasonal contracts with automatic scheduling, which is convenient but make sure you can pause or cancel without excessive fees.
Do You Have References or Reviews?
Request at least two local references from customers with systems similar to yours. Ask those references specifically: Did the provider show up on time? Did panels look noticeably cleaner afterward? Any issues with their invoicing or follow-up?
Check Google, Trustpilot, or solar-specific review sites for patterns. One negative review isn't alarming; multiple complaints about damage or bait-and-switch pricing are.
Frequently Asked Questions
Q: How do I know if my solar panels actually need cleaning? Check your energy production via your inverter's app or monitoring system; a sudden 10–15% dip suggests dirt buildup. You can also visually inspect panels for visible dust, bird droppings, or pollen film.
Q: Can I clean my panels myself to save money? DIY cleaning risks personal injury, voiding warranties if you damage seals, and suboptimal results using tap water (which leaves mineral deposits). Professional equipment and deionized water justify the $200–400 cost every 6–12 months.
Q: Will cleaning void my solar panel warranty? Not if done correctly by a reputable provider. Improper cleaning (high-pressure washers, abrasive materials, harsh chemicals) can void coverage, so always confirm the provider uses approved methods.
Find and compare trusted solar panel cleaning providers in your area on Mercoly to get vetted quotes and make an informed decision.