Cordless window cleaning robots in 2026 run 40-90 minutes per charge depending on suction level. The honest figure for a real facade pass is closer to the low end, because high suction drains cells fast.
Battery claims deserve the same scepticism as vacuum-cleaner runtime claims. Here is how the numbers break down and when corded still wins.
How long does a cordless window cleaning robot really last?
| Suction mode | Typical runtime | Clean area per charge |
|---|---|---|
| Low (light dust) | 70-90 min | 60-90 m2 |
| Medium | 50-70 min | 45-60 m2 |
| High (dirty glass) | 35-45 min | 25-40 m2 |
The trap is quoting low-mode numbers as the headline. On dirty glass you will run high suction, and the runtime drops by roughly half. Plan around the high-mode figure if your glass is anything but lightly dusty.
Is cordless worth the trade-off?
It depends on your tether setup. A cordless machine removes one snag risk and speeds rigging, which matters on complex facades and skylights. But it adds battery management: spare packs, charge cycles and a hard stop mid-run. On a big, simple curtain wall, a corded machine with a managed cable is often faster on balance because it never stops to swap. For obstacle-heavy glass roofs, cordless usually wins. Our Lingyun Y3 review shows a cordless unit on a stepped glass run.
What drains the battery fastest?
- High suction on hot glass, which forces the fan to work harder
- Frequent slope climbing and obstacle crossing
- Cold weather, which cuts lithium capacity noticeably below 10 C
- Heavy spray volume, which adds pump load
How should you plan a shift around battery life?
Match the machine to the run length, not the whole building. A 40-minute high-mode window covers about 30 square metres of dirty glass, so a large facade needs either spare packs rotating or a corded unit. Buy one extra battery per machine and keep it on charge; the swap is faster than waiting for a full cycle. Compare runtime behaviour across units in our all skylight robot reviews.
Who should not go cordless?
Buildings with long, uninterrupted glass runs and a fixed rigging point are better served by corded machines. Cordless shines where cables snag, where setup is fiddly, or where glass is broken into small panes with frames. If your facade is one big clean rectangle, cordless is a compromise you do not need.
Should you keep a spare battery or a spare machine?
A spare battery first. It is cheap relative to the machine and removes the biggest cordless risk, the mid-run stop. One extra pack per unit, kept on charge, turns a 40-minute window into a continuous shift. A spare machine only makes sense once you run two crews.
Charge discipline matters too. Lithium packs last longest when kept between 20 and 80 percent and stored cool. Charging to full and leaving a unit in a hot van cuts pack life noticeably, which is a real cost on sites where the machine lives in a vehicle.
How do you decide between corded and cordless in practice?
Count the snag points on your facade. Every corner, ledge and box that a cable could catch is an argument for cordless. Every long, straight run with a fixed anchor is an argument for corded. Buildings rarely fall fully into one camp, so many teams keep one of each: cordless for complex glass, corded for the long repetitive faces.
How do cold and heat change runtime?
Lithium packs lose capacity below about 10 degrees Celsius, sometimes by a third, so a winter facade run can end sooner than the summer figure. Heat is a different problem: on glass above 45 degrees the fan works harder to hold suction, which drains the pack faster even though the battery itself stays warm. Plan winter runs with a spare pack and summer runs earlier in the day. Neither is a defect, but both surprise owners who only tested in mild weather.
What does a real shift plan look like?
- Arrive early, when glass is cool and wind is low
- Rig once, run the longest face first
- Keep one pack on charge for the switch
- Reserve the last hour for edges and frames
- Log the run so the next shift can plan
Cordless machines reward planning and punish improvisation. A pack that runs flat mid-face means a pause, a climb and a restart, which erases the setup advantage cordless was meant to deliver in the first place.
Can you run a cordless machine from a power bank?
Some models accept a top-up from a portable station, which can extend a shift without a wall socket. The catch is weight and charging time: a large station is itself a thing to carry, and topping up a pack mid-shift takes longer than swapping to a spare. For most sites, a second battery is simpler and lighter than a power station. Reserve the station for remote roofs where no socket exists and the run is short.
If your site has no power at all, treat runtime as the hard limit and plan the cycle around it, rather than hoping a top-up will rescue a badly sized plan.
Key Takeaways
- Real runtime is 35-45 min on high suction, not the 90-minute headline.
- High mode covers roughly 25-40 m2 of dirty glass per charge.
- Cold weather and slope climbing drain cells fastest.
- Corded still wins on long, simple facade runs; cordless wins on complex glass.