Search for this and you will find a per-panel rate quoted with great confidence and no conditions. It is not useful. The same 200 kW array can be legitimately quoted at rates that differ by a factor of three, and in most cases both suppliers are being honest about different jobs.
Why we won't print a rate card
Because a number without the site attached is how people end up comparing a full seven-stage clean with demineralised water against two men and a bucket. We would rather explain what moves the price, so that when you have three quotes in front of you, you can see which of them is actually for the work you want done.
The seven things that move the price
1. Access
The largest single variable, and the one owners consistently underestimate. Ground-mount with vehicle access is cheap. A fourth-floor terrace with no service lift, reached by a ladder through a hatch, is not — because everything, including water, goes up by hand.
2. Water, and where it comes from
If there is a tap on the roof, water is nearly free. If it arrives by tanker, it is a line item. If the local supply is hard — much of Maharashtra — then cleaning properly means treated or demineralised water, which costs more and is the difference between a clean panel and a panel with a permanent mineral haze.
3. Array geometry
Long uniform rows suit mechanised cleaning and the rate drops. Mixed tilts, staggered blocks, walkways in odd places and rooftop obstructions all push the job back towards manual work, and manual work is priced in hours.
4. How dirty it is
First cleans on a neglected array cost more than routine cycles, sometimes substantially. Bonded soiling, lichen, cement splatter and bird deposits that have baked on for a season need treatment, not rinsing. Any supplier quoting a routine rate for a first clean has not looked at the array.
5. Frequency and contract length
A one-off clean carries the full mobilisation cost. The same site on a scheduled annual contract spreads that across visits and lets the crew plan routes, which is why AMC rates are meaningfully lower per visit than call-out rates. This is real, not a discount trick.
6. What else is in scope
Cleaning plus a visual module inspection plus an inverter check plus a structural look is a different service from cleaning. It should cost more. It usually saves more, because the expensive failures are not on the glass.
7. Who is actually doing it
Trained crews with insurance, safety equipment and a defined method cost more than two people hired for the morning. That gap is the whole argument, and it shows up on your roof long before it shows up on the invoice.
Comparing two quotes properly
Put them side by side and check that both state:
- The cleaning method, in words — not “professional cleaning”
- The water source and whether it is treated
- Whether the price includes water, or it is your tap and your tanker
- What inspection, if any, happens during the visit
- What you receive afterwards
- Who carries the insurance if a module is damaged
- Whether the rate is for a first clean or a routine cycle
Two quotes that differ by 40% usually differ on three of those lines. Once they are filled in, the cheaper quote is sometimes still the right one — and now you know why.
What the cheapest quote is leaving out
Not always something bad. Sometimes a local operator with low overheads and a site ten minutes away is genuinely the efficient answer for a small rooftop, and we will say so.
But the recurring pattern in the lowest quotes we see is: untreated hard water, no inspection, no record, no insurance, and people walking on the modules to reach the far rows. The first three cost you information. The last two can cost you a module, and micro-cracks from foot traffic do not appear on the day they are created.
Working out what it is worth
The useful calculation is not the invoice. It is the invoice against the generation you recover. Take the units your plant produced in the fortnight before a clean and the fortnight after, adjust roughly for sunshine hours, and price the difference at your tariff. Do this twice and you will know what cleaning is worth on your specific roof — which is a far better basis for negotiation than any rate card.
If your generation data is not in a shape where you can do that, that is itself the finding. It is also where a screening or a site visit is worth more than another quote.
Related: What an O&M contract should include · AMC options