A mid-range skylight cleaning robot covers 150 to 250 m² an hour in 2026. The real limits are the water tank, which handles roughly 400 to 700 m² of glass, and battery runtime, typically 3 to 5 hours. Plan a window around those two numbers, not around peak speed.
Manufacturers quote the best square-metre rate. On a real roof, edge work, repositioning and refills cut that figure. Knowing where the time goes is what turns a spec sheet into a schedule you can actually run.
How many square metres per hour is realistic?
On a flat or low-pitch glass roof with clean edges, 200 to 250 m² an hour is achievable. Add a steep pitch, frequent panel joints or obstacles and the same machine drops to 120 to 160 m². The difference is not the cleaning itself; it is the repositioning between zones and the slower pace needed on a slope.
How much glass does one tank cover?
Tank size ranges from about 8 litres on compact frames to 30 litres on industrial units. At a typical consumption of roughly 40 to 60 ml per m² of glass, that works out to 400 to 700 m² per fill for the larger machines. A 20-litre tank on a 600 m² roof likely means one refill mid-job, so plan a water point at roof level.
| Machine class | Tank | Glass per fill | Runtime |
|---|---|---|---|
| Compact (Lingfeng S1) | ~8-12 L | 200-300 m² | 2-3 h |
| Mid (Lingyun Y3) | ~15-20 L | 350-500 m² | 3-4 h |
| Industrial (Lingkong K3) | ~25-30 L | 550-700 m² | 4-5 h |
What runtime should you expect per charge?
Battery runtime lands between 2 and 5 hours depending on class and load. Cold weather cuts that noticeably; expect a 15 to 30 percent drop when the glass itself is under 5 degrees Celsius. A spare pack effectively doubles your window without a long charge break, and on a big roof it is worth the extra cost.
How do you plan a cleaning window?
- Measure the glass area and divide by the conservative rate for your pitch.
- Count refills: area divided by glass-per-fill tells you how many water stops.
- Check runtime against the window length; add a spare pack if it is tight.
- Leave 20 percent slack for repositioning and weather.
A 900 m² atrium roof at 200 m² an hour is roughly 4.5 hours of cleaning. With a mid-range machine that is two tanks and one battery swap. If your window is only three hours, you need either a bigger class or two visits.
Which roof shapes waste the most time?
Curved vaults and heavily segmented roofs are the worst offenders. Every panel joint forces a slow-down, and steep sections cut effective speed. A flat 600 m² roof might finish in three hours; the same area split into forty curved glass segments can take five. Layout matters as much as machine class.
If you share your roof area, pitch and window length, the team can recommend a class and water plan. Start from the contact page.
Does glass angle change water consumption?
Yes, noticeably. On a steep pane, water runs off faster and less of it clings to the surface, so a first pass uses more to wet the glass. Site studies suggest a steep glazed face can consume 10 to 20 percent more water per square metre than a flat one. On a big sloped roof, that changes how many tanks you need.
How does dirt level affect the numbers?
A heavy first clean after construction or a long idle period can take two or three passes. That triples water use and roughly halves the coverage per hour. Budget the first clean separately from the routine cycle, because mixing the two makes the routine numbers look worse than they are.
When should you add a second machine instead of a bigger one?
If the roof is split into separate zones with no easy route between them, two compact machines often beat one large one. They cover more area in the same window and can work in parallel. One large machine wins when the roof is a single continuous run.
How do you keep coverage high across a long run?
Work in long uninterrupted passes and minimise turns. Every stop and reposition costs seconds that add up over a 200 m roof. A machine that holds a straight line and returns to a dock covers more than one that wanders. Route planning, not top speed, is what raises the real hourly figure.
What does a realistic cleaning window look like?
For a 900 m² low-pitch roof with a mid-range machine: about 30 minutes of setup and water staging, four to five hours of cleaning across two tanks and one battery swap, then 20 minutes to pack and recharge. That is a full shift for one operator, and it fits a single day if the weather holds.
Winter changes the plan again. Cold glass cuts battery runtime by 15 to 30 percent, so add a spare pack or shorten the window. Water behaves differently too, and some solutions need a warmer mix to work on chilled glass. Adjust the schedule seasonally rather than running the summer plan all year.
What is the single number to watch?
Square metres cleaned per hour, measured on your roof, in your weather. Track it monthly. If it drifts down, something changed: a worn blade, a clogged filter or a new obstacle. That one number catches most problems before they become visible on the glass.
Key Takeaways
- Realistic coverage is 150-250 m² an hour; steep or segmented roofs drop toward 120.
- One tank covers about 400-700 m² on larger machines at 40-60 ml per m².
- Runtime is 2-5 hours and falls 15-30 percent in cold conditions.
- Plan windows from tank and battery limits, with 20 percent slack.