A skylight cleaning robot runs one dry-to-wet cycle in about 90 to 150 seconds per lane, but effective throughput on a real glass roof lands nearer 300 to 420 m2 per hour once water swaps and lane re-anchoring are counted. The machine is not the bottleneck; the water and the roof geometry are.
Buyers ask for a single number. Suppliers hand over a spec sheet that says 400 m2/h, and everyone nods. Then the machine shows up, and the first week’s log looks nothing like the brochure. That gap is worth understanding before you sign, because it decides how many machines you actually need.
What does one cleaning pass actually involve?
A pass on a skylight cleaning robot is not a single motion. It is a sequence: lower onto the glass, run the brush or microfiber roller, lay down water or cleaning solution, then drag the squeegee blade across before the liquid dries. Reverse the head and repeat.
On flat laminated glazing, that sequence is quick. On a 15-degree sawtooth roof or a faceted atrium, the robot slows to keep traction, and you lose maybe 10 to 15 percent of the pass speed. Curved glazing costs more again.
- Wet-down: 6-10 seconds per lane width
- Brush dwell: 20-40 seconds depending on soiling
- Squeegee pull: 15-25 seconds
- Repositioning: 20-45 seconds, the quiet killer
Why does the spec sheet say 400 m2/h?
Because the spec assumes continuous motion with no water stops and no obstacle detours. Manufacturers measure on a clean, empty, square glass field. Nobody cleans an empty glass field.
Real roofs have mullions every 1.5 to 2 metres, roof hatches, vent stacks, and expansion joints. Each interruption costs a stop, a lift, and a re-seat. A 1,200 m2 atrium with 40 mullion crossings can easily add 25 minutes to a run that the spec called 3 hours.
| Roof type | Brochure rate | Field rate | Loss |
|---|---|---|---|
| Flat framed skylight | 400 m2/h | 340 m2/h | 15% |
| Sawtooth factory roof | 400 m2/h | 280 m2/h | 30% |
| Faceted atrium | 400 m2/h | 230 m2/h | 42% |
Where do you actually lose the time?
Water. A robot carrying an 8-litre tank covers roughly 90 to 130 m2 before it needs a refill. On a 1,200 m2 roof that is 9 to 13 refill stops, each taking 3 to 5 minutes including the walk back to the tap. That alone is 40 to 65 minutes of dead time per full clean.
Fleet units like the Lingkong K3 pair a smaller onboard tank with a tether or a support cart, which cuts refill frequency but adds hose management. Neither approach is free. The decision is whether you would rather lose minutes to walking or lose them to hose drag.
Battery is the second cost. Cold weather drops usable capacity. Below about 5°C, expect 15 to 20 percent less runtime, so a machine rated for 4 hours finishes nearer 3.2 hours. Plan the schedule around the worst month, not the best one.
Should you buy one machine or two?
Buy one if…
Your glass area is under 2,000 m2, you clean monthly or quarterly, and a single overnight window is enough. One robot on a 1,200 m2 roof takes about 4 hours of real work plus travel and setup. That fits a night shift without drama.
Do not buy two if…
You only have one operator and one charging bay. Two machines triples your logistics, not your output, because someone has to shuttle water and swap batteries. We have seen sites buy a second unit before fixing their water plan and end up no faster than before.
What should you measure in a paid trial?
Do not accept a demo on clean glass. Ask the supplier to run a full lane on your dirtiest section, and time four things: time per lane, water consumed, refills needed, and the number of manual re-seats. That last number tells you whether the navigation handles your mullion pattern or whether an operator will babysit it all night.
If a supplier cannot produce a lane time on your own roof, treat the spec sheet as marketing. Compare the numbers against our m2-per-hour breakdown and then talk to us through the contact page.
Key Takeaways
- One pass takes 90-150 seconds; real throughput is 230-340 m2/h, not the 400 m2/h on the brochure.
- Water refills cost 40-65 minutes per clean on a 1,200 m2 roof of 9-13 stops.
- Cold weather below 5°C cuts runtime 15-20 percent, so schedule against your worst month.
- Fleet designs like the Lingyun Y3 trade walking time for hose management, not for zero downtime.
- Time four things in a paid trial: lane time, water use, refills, manual re-seats.