A window-cleaning robot fixes itself to the glass by suction, drags a damp pad across the pane in a set pattern, then beeps to be lifted off again. That is the whole trick, and it is worth understanding before you spend anything. Across a test of 30 machines, the blunt conclusion was that these robots earn their place only in a narrow set of homes. This guide covers how they work, what none of them can do, the two that are worth considering, and the rest of the field.
What follows is recorded testing, translated. Nobody at Truthful Reviews has run one of these up a window.
How they stay on the glass
The mechanism is negative pressure. A fan pulls air out from underneath the machine so that it clamps itself to a smooth vertical pane, and it stays there only for as long as it has power. The fan is not doing the cleaning — that happens through movement, as the robot draws the cleaning pad on its underside across the glass. Because the fan is doing a vacuum cleaner's job, these machines sound like one: around 80 dB in use, with the field spread across 70 to 80 dB.
Almost every model has a battery, but in most cases it is a reserve rather than a power source. It holds the machine on the pane for roughly 15 minutes if mains power is interrupted, and the robot emits a loud, high-pitched beep throughout. Only a couple of designs on the market run their normal cleaning work from a battery at all; everything else needs a live connection.
A tether is part of every machine in the test. Each one anchors either by carabiner clip or by suction pad, and it stays attached for the whole cycle, alongside the mains lead on the models that need one. That is the reason the category never feels tidy in use.
The newer idea, borrowed from robot vacuums, is the station: a portable box weighing several kilograms that holds a battery, stores the robot and its accessories, and frees the machine from needing a socket near the window being cleaned. Two of the machines here work that way.
Once the robot is on the glass it runs an N or Z pattern — the letters describe the shape of the route rather than standing for anything. N suits tall windows, Z suits wide runs of glazing.
What none of them can do
They cannot change pane. When a robot finishes, it returns to its starting position and beeps to be taken down. It cannot move to the next window, and no model cleans the frame. So the cycle repeats by hand every time: lift the robot off, rinse and re-wet the pad, carry it to the next pane, rearrange the line, choose a programme. Nothing about this is fully automatic.
They leave a strip at the edge. The contact sensors at the corners project further out than the cleaning pad does, so the textile never quite reaches the frame. A narrow unswept strip beside the frame is the normal outcome, and it is worse on the models built around two circular pads, which cannot reach into corners at all by design.
They cannot work overhead. The suction is tuned so that weight and grip balance on a more or less vertical pane, which is precisely what lets the robot move at all. On shallower angles that balance fails and the machines simply go nowhere. Not one of the models tested can work upside down, so conservatory and lean-to roofs are outside the category.
They leave streaks. Every machine does, on every pass. You often only see them when the sun comes through, but they are always there, and the result is a long way from a careful hand wash. That is the state of the art rather than a fault of any one model.
They struggle with real dirt. Dust, pollen and fresh fingerprints come off. Anything dried on gets smeared on the first pass and needs two or three more, or finishing by hand. On badly soiled glass, some machines stop and report an error.
They wander. During testing several robots lost their bearings mid-run — stopping dead, turning in unhelpful circles, or driving into the frame again and again. Frameless glass makes this worse, because the contact sensors have nothing to hit and the drop sensors have to do the work instead.
The picks
Top pick — Ecovacs Winbot W2S Omni
The box holds the robot, the Omni station, a power adapter, a safety line with carabiner, two microfibre pads, a bottle of cleaning solution and printed documentation. There is no remote: you drive it from buttons on the robot, buttons on the station, or the Ecovacs Home app.
The robot measures about 27 × 27 cm and stands 7.6 cm tall, weighing roughly 2 kg. The plastic housing on robot and station feels solid and cleanly finished, though the robot itself only reads as moderately premium. The imitation-leather carrying strap is useful, if standard across the category. Pads attach by hook-and-loop and come off quickly for washing. The station is built as a case with a handle, swallows the robot and its accessories, and at over 5 kg is heavy but still portable.
It grips at up to 8,000 Pa and monitors that pressure continuously. Station and robot are joined by a combined power and safety cable that the station reels back in at the touch of a button, and the station holds itself down by suction pad on any reasonably smooth floor.
The main battery sits in the station and powers the robot as it works. The claim is 110 minutes of running; measurement put it nearer 70 minutes. Extrapolated, that covered around 15 m² of glass in the thorough mode, although the cleaning-fluid tank needs refilling along the way. Plugged in, it can clean and charge at the same time, which effectively removes the limit. A full charge takes just under three hours. There are no published figures for charge cycles or battery life.
In use, the pad is dampened, the small tank filled, and the robot set against the pane, where it grips and then works methodically in lanes. Depending on the mode it took 2.5 to a little over 6 minutes per square metre to clear ordinary marks — fingerprints, pollen, dust — reliably. Heavier stains want several passes or a hand finish. The Tru-Edge system, which drops small scrubbers at the sides, visibly improves edge cleaning compared with older Winbot models, though finishing by hand is usually still needed.
Set-up help is good: a short guide sits inside the station lid, and the app walks through the first cycles with an assistant and illustrated prompts. The structure is clear and jargon is mostly explained, with the odd clumsy translation that does not get in the way.
For a household with a handful of small windows this is hard to justify. For large panes, especially awkward ones, the comfort it buys is more defensible — provided you accept that the glass will not come up as clean as it would by hand.
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The luxury pick — Ecovacs Winbot W3 Omni
This takes the robot-vacuum station idea one step further: the station washes the pad. That is what the large porthole on the front is for, and it does make it look like a small washing machine.
Before the first run the clean-water tank is filled, the pad carrier prepared and the robot paired with the app. The pad is fixed to a removable plastic frame, and preparing it means letting the station clean it for a minute and then removing the excess water — slower than holding a cloth under the tap and wringing it out, if considerably more entertaining. Two hands are needed to take the frame off, and it sits a little loose going back in, so the front flap wants closing firmly.
A 5 m cable links station to robot and serves as both power supply and safety line. The station weighs about 10 kg, stands firmly on the floor and grips smooth surfaces by suction as well, which is what lets the robot work higher windows without the station being anchored to anything. Carrying that weight between floors, or putting it away afterwards, is the other side of the bargain. The station battery gives around two hours of running, and the system can stay on mains indefinitely. Surfaces up to 45 degrees of incline are within range.
The cable retracts on a button press. Oddly for its size, the station offers no enclosed storage for the robot: it clips to a fold-out bracket on the outside, which looks improvised, takes up more room in transit and protects nothing.
Navigation, badged WIN SLAM 5.0, plans a route and recognises frames and smaller obstacles — a bird-protection sticker was picked up and partly driven around during testing. After that the robot works its lanes calmly and evenly. A pane of about 1.5 m² took a little over five minutes on a single interior clean, and six minutes on the intensive setting meant for outside faces.
Six physical spray nozzles wet the glass, three of them working as a wide-angle system depending on the direction of travel. Dust, pollen and limescale came off very thoroughly, and greasy fingerprints left only slight residue. In raking light the result was largely even, without obvious clouding or heavy smearing — although light streaks still show in direct sun, and dried-on dirt still needs several passes or hand work. No window robot has the concentrated force of scrubbing by hand.
Edge cleaning is better than on its predecessors. Small TruEdge brushes at the sides drop against the frame and spin at up to 200 rpm along the edge, loosening dirt and pushing it towards the main cloth. It is still not edge-to-edge: depending on the window and the thickness of the seal, a strip several millimetres wide stays untouched, and corners are never fully cleaned because the brushes are round. Compared with machines that have no edge brushes at all, though, the missed area is smaller.
The headline feature is Vortex Wash. After a run the cloth frame is taken off the robot and dropped into a separate compartment in the station, where 16 jets rinse the pad, four rotating discs work the fibres mechanically, and a scraper strips the dirty water away. It takes about a minute, a little longer on the intensive setting. Clean and dirty water are collected separately and the compartment can run its own self-clean cycle. The result is good: on normally soiled glass the cloths come back visually clean, which saves a trip to the sink or a run through the washing machine. The TruEdge brushes still want cleaning by hand, and taking the pad carrier off and refitting it remains the user's job.
Control is by a single button on the robot, a display and buttons on the station, or the app, with quick, deep, edge, spot, zone and intensive modes among the options, plus manual driving from the phone. The range of modes makes it easy to match the setting to the dirt, and a straightforward clean does not need the app at all. The station's nested menus could be clearer, though they become second nature.
The app has real gaps. On first use it does not explain how to use the robot — that the cloth frame needs washing before the first run, for instance. It is also not fully responsive: with enlarged system text, the Next button during Wi-Fi set-up sits off-screen, the page will not scroll, and set-up simply stops there.
Set against that, it delivers one of the best cleaning results in the category, with systematic navigation, comparatively good edge work, long battery running and a washing station nothing else offers. The costs are footprint, weight and price. For a few reachable windows it is far too much machine. For a lot of large glass, or panes a long way from a socket, it buys more comfort than anything simpler — and at about 60 dB it is genuinely quiet for the category.
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Also tested
Dreame C1 Station — the other station-based machine. The station carries spare cloths, cleaning fluid, a battery and a 5.5 m cable with automatic retraction, and anchors the robot twice over, by carabiner and by a suction pad underneath. The square robot worked panes systematically in Z and N patterns, and the Corner Clean brushes at all four corners plus adaptive spray control gave even results on normally dirty glass. Noise is the problem: up to 73 dB(A), and the tone was judged the most irritating in the group. The app is attractive and functional and the glass top plate is a nice touch. The claim is up to 90 m² per charge, which is optimistic in practice. Streaks remained, edges were not quite as clean as the W2S Omni's, and the bigger battery pushes the station to nearly 8 kg, which makes carrying it less pleasant. Search Amazon UK · Search Amazon US
Ecovacs Winbot Mini — a compact machine for small and awkward panes, about 21.5 × 21.5 × 5.5 cm and just over 1.3 kg, running from a mains adapter with a reserve battery. Instead of a conventional nozzle it atomises the fluid through an ultrasonic twin jet. The stated noise level is around 63 dB; measurement put it at about 65 dB. It works the pane in lanes and, thanks to a reshaped edge, cleans close to the frame without a bumper — about as well as the rest of the field. Because it is small it took considerably longer per pane than the W2S Omni or the C1 Station, which is the trade for being the best fit on small glass. Search Amazon UK · Search Amazon US
Kärcher RCW 4 Extra+ — built for large, hard-to-reach and frameless glass. Its big rectangular cloth is fed continuously by six nozzles, and four corner sensors pick up frames, obstacles and the edges of frameless panes. There are four automatic programmes and a manual mode. On the plus side, a 150 ml tank, a light robot at around 1.5 kg, and a high nominal cleaning speed. Against it: no operating battery at all, so it has to stay connected to the mains throughout, and no app or automatic cloth washing. On the glass it did not stand out from the field — tidy across the surface, adequate at corners and edges, with the usual streaks visible in sunlight. Search Amazon UK · Search Amazon US
Kärcher RCW 2 Extra+ — two rotating cleaning discs and two ultrasonic nozzles. In theory the rotation should loosen stubborn dirt better than a cloth that merely glides; in practice it did not, and the oval body with round pads reaches corners poorly by design. On the test window it ran along the frame at top and bottom but only approached it left and right, leaving triangular patches between the two round pads and the frame that were never reached at all. Circular streaks — halos — show up later in sunlight. It is light at around 1.1 kg, offers several automatic programmes and manual control by remote, and comes with a cleaning concentrate. There is no app, it is not designed for frameless panes as the RCW 4 is, it needs a permanent mains connection, and at about 70 dB it is not quiet. Search Amazon UK · Search Amazon US
Ecovacs Winbot W2 — a two-in-one connector combines power supply and safety line, so only one lead leaves the machine. Set-up is easy, with a voice prompting each step, and the app acts as manual, error display and control centre, though it requires an account. Quick, thorough, deep and edge modes are joined by manual driving from the phone. It handles dust and fresh, small marks well; heavier soiling gets smeared on the first pass and needs a second or third run. Faced with large dried-on marks it stopped and sounded an error. Its shape lets it reach into corners and there is a dedicated edge mode, but those areas still do not come up clean. At about 68 dB it is one of the quieter machines. Tilted windows are no obstacle; horizontal surfaces are refused outright. Search Amazon UK · Search Amazon US
Ecovacs Winbot W2 Omni — the same robot supplied with a multifunction station. The station's 4,500 mAh battery is the point: it lets the robot run without a socket nearby, with a claimed 110 minutes of cord-free work. The station doubles as a carrying box holding the adapter, two microfibre cloths and cleaning solution, and it reels the cable in automatically. That cable is again both power lead and safety line, and the station anchors itself to the floor by suction, so no carabiner is needed. Three buttons — power, cable retraction and mode — mean it can be used without the app. The cleaning did not convince: in every mode, streaks were left behind clearly enough to trace the route afterwards, and heavier dirt was smeared rather than lifted. Search Amazon UK · Search Amazon US
Hutt 10 — combines a rectangular dry cloth with a rotating, continuously dampened round pad, running upright with the dry cloth above and the wet pad below, so it should loosen dirt and then wipe the pane flat. Light soiling — dust, pollen, limescale — came off adequately, it is comparatively quiet, and it runs close to the frame. With more dirt it reaches its limit quickly and picks it up only with visible streaks, and no real advantage from the pad combination was apparent, though the halos are reduced compared with twin-rotating-pad machines. Corners are not fully cleaned, there is no app, and the battery is a power-cut reserve only. Search Amazon UK · Search Amazon US
Klamer Window Robo Pro 3400 — compact and mains-powered, with a reserve battery, an app and a remote, measuring roughly 24 cm on each side. Two water tanks, each with a single nozzle front and rear, mist the glass. Programmes can be set through a Tuya app and the remote, and it is not especially quick. It cleaned vertical glass reliably with the streaking typical of the category: light soiling such as pollen came off well, while older water marks and heavily dirtied areas needed a second pass or hand finishing. It appears to slip slightly to one side at times, running its lanes a little askew, without causing trouble. It was the second-loudest machine in the November 2025 round of testing. Search Amazon UK · Search Amazon US
One thing to check before you buy. The choice on the shelves is smaller than it looks. A great many of these machines are the same hardware sold under different names, which is why the same design keeps reappearing across brands — and identical models can be priced very differently depending on the badge. It is worth comparing specifications rather than names.
Who a window robot actually suits
If you are hoping to be freed from a chore, you will be disappointed. These machines cannot be left to get on with it, they do not clean as thoroughly as a person, and they are nowhere near as quick.
They start to make sense with lots of large panes. Picture windows and long runs of glazing are where a robot's slow, methodical lane pattern is worth having, because it is covering area you would otherwise cross by hand many times over. They also suit tall glazing, where cleaning by hand means setting a ladder, doing a metre, climbing down and moving it along. A robot four metres up removes that repetition entirely; arranging the line is the only part left to think about.
They are poor value on small glazing-bar windows, where they either fail outright or create more work than they save, and they are little fun on small older windows, because you spend the session carrying the robot from one pane to the next.
They are a smaller help than they look for anyone who cannot clean their own windows, since the line still has to be arranged first and the robot still has to be lifted onto each pane and taken off again.
And they are, unapologetically, a gadget. Watching a small box drive itself around a vertical pane is genuinely good fun, and for anyone who cleans their windows once a year and is not chasing perfection into the corners, that may be reason enough.
How they were assessed
Because ordinary test windows are not dirty enough to tell machines apart, a standardised soiling mixture was applied by hand: the panes were sprayed with a solution of pollen, water and oil, and every test was run on that prepared surface.
Each of the 30 robots cleaned a pane measuring about 0.8 × 1.9 metres — roughly 1.5 m². The time taken by each mode was recorded and the noise level measured during the run, and every machine used the same glass cleaner so the comparison stayed fair.
To check how they behave on smooth surfaces with no boundary, the robots were also run on horizontal tabletops, which shows whether a machine can orient itself without a frame to find. Build quality and ease of use were assessed at the end, along with the accessories, special functions and individual quirks of each model.
The short answers
Which is the best window-cleaning robot? The Ecovacs Winbot W2S Omni. It cleans solidly and its station carries a battery, so there does not need to be a socket near the windows you want cleaned.
How long does the battery last? In most machines the battery is purely a reserve for a power cut, holding the robot on the glass for around 15 minutes. Only a couple of models on the market draw their normal working power from a battery; the rest need a mains connection.
Do any of them clean the frames? No. Frames are out of reach for every robot, and even the smallest step up is an impassable obstacle.
How long does one window take? It depends on the model and the size of the pane, but most robots need roughly seven to ten minutes per square metre.
How heavy are they? Most weigh between 1 and 2 kg.
How loud are they? Between 70 and 80 dB in operation, which puts them on a par with an ordinary domestic vacuum cleaner.
