Window cleaning robots are supposed to take the drudgery and effort out of window cleaning. Overall, that is correct, but we found some exceptions to that supposition.

It is a reasonably self-contained device that attaches to indoor and external windows and methodically cleans the glass pane before being manually moved to the next. It

In a previous retch review life, I had exposure to Window cleaning robots and have been using one for the past two years. Given that these parameters are tempered by actual use, we convened our user panel to see what they expected.

The panel concluded that robot window cleaners might do a reasonable job. Still, they are by no means unattended cleaning as there is a constant need to move the device to the inside/outside and new glass panels.

There are two main shapes of window cleaning robots. We will call these WCRs for now (as ECOVACS has trademarked WINBOT).

Both have a fluid reservoir that uses window cleaning fluid and water to cut through grime. Regardless of which one, you must add the human touch by moving it to new panels and touching up any streaks.

Effectiveness means 100% coverage (corners etc.) and streak-free cleaning. The experience here is that they don’t do corners, and it may be necessary for multiple passes, for example, a dry run to remove dust and a wet run to clean – effectively doubling the time.

Winner: Both types do a similar job

As we found with robomops, the critical issue is changing microfibre pads frequently to avoid dirty pads leaving streaks on the glass.

Our experience with the dual rotating Hobot 388 is about 15m2 of wet cleaning before you change pads.

We can only assume fixed flat pads will need more frequent changes as the leading edge tends to do much of the work and gets dirty faster.

Winner: Dual rotating pads appear better and offer some ‘elbow’ grease. We are not aware of the effects of any vibrating pad yet.

The jury is out on what produces the best results. The answer is that rotating pads are better for marine and dusty environments as they better cut through the salt/dust grime. The overall finish is not as good as square pads.

Square pads are for suburban use where windows are in better condition and leave glass cleaner.

Water is only 40% effective at removing salt spray and environmental grime. A good window cleaner has cutting power and will remove this type of scum.

Don’t use other cleaners as they may block the 15um nano-sprays.

Winner: Use the recommended cleaner

Our experience with two Hobot WCRs is that they use a 15um (microns) nano-spray to wet a portion of the window below the bottom pad. It reduces the potential to leave water marks or streaks as there is insufficient volume.

Some WCRs have centre-wetting vents that appear to use a lot more liquid. Less is best.

But also remember that fine spray is subject to the wind blowing it off course. Clean on a still day.

Winner: nano-spray spray over pad wetting.

The square type often has triangle cuts at the four edge points, meaning it cannot clean corners. The twin rotating pads cannot reach corners. You will need to clean these areas manually.

Vacuum style creates a vacuum to adhere to glass. These come with a safety rope to stop death dives – great idea but not always convenient.

Magnet mounts are safer because you place a rubberised magnetic pad on the opposite side of the glass, and the magnets hold the device in place. But there are a few downsides. You may be unable to access the other side of the glass. Magnets strong enough to go through thick glass are heavy. They do not work on thicker glass and are not good on curved glass. The magnet pad can scratch the glass.

Avoid those with larger tractor wheels (generally the magnetic type), as the wheels can leave marks if wet.

Neither type can handle negative slopes (like inside sloping skylights) over about 45° as the weight and slip factor vectors cross over, leading to the death dive.

The Hobot are both mains powered. The onboard battery acts as an uninterruptable power supply (UPS), giving up to 20 minutes of vacuum adherence in case of a power failure. That means you need a 240V power point nearby.

Battery-operated WCRs are heavier and have shorter run times.

The Hobot has a 5m DC cord. The battery is small and light, safeguarding against losing mains power. This means it can clean all day without a charging break.

But if you use an AC extension cord, remember that all WCRs can only carry their weight and a few metres of a lightweight DC power cable and safety rope. They cannot hold an AC cord weight, especially if it is lifting it off at an angle to the ground.

Some vacuum models can break the thinner 3mm glass. Thicker glass can impact magnetic models. Standard 4-10mm glass is fine.

Winner: Lighter devices are better for thin glass.

You must remove screens before cleaning the window surface. Most flyscreens have twist clips, some slip into window frames, and some use magnets. If your home is older, then plan on breaking a few clips.

If you have permanently affixed security screens, the only way to clean the window is to remove it.

Take care if anything protrudes into the glass area. Most WCRs will get stuck (except those with some AI to recognise this).

Winner: See if AI handles this

WCRs make a noise – up to 70dB at 1m, and that is fine. Magnetic WCRs are quieter.

All need dry glass, meaning no rain, snow, or high humidity. Don’t use it on windy or overly hot days.

These prevent a death dive after sudden detachment. No WCR can withstand a few metre fall without breaking something.

The real question is where to attach the safety rope, especially for indoor windows when there is only a ceiling overhead.

The answer will only come from experience and confidence with your WCR. If it has had no death-wish issues, perhaps trust it. Why not place a pillow at the window’s base to break its fall?

Winner: Use safety rope where possible, especially outdoors.

The panel said that WCRs should be faster than doing it with a squeegee.

The Hobot 388 takes about 4 minutes per 1m2, and you have two sides and two passes (dry and wet). We have no experience with other brands, but 4 minutes per m2 overall seems reasonable.

By definition, a robot (be it a vacuum, mop, lawnmower etc.) should be able to be left unattended to do its job. In our experience, no amount of AI or clever navigation means you can leave a WCR unattended.

After every window pass, you need to turn it off, remove the safety rope, move it to the next window and repeat. All types have this issue, and your peaceful time doing other things will suffer regular interruptions.

Winner: Draw, but faster clean times are better

Most WCRs boast AI, but it is just simple pattern cleaning. Place it at the window’s top corner and let it logically clean in a u-pattern as it descends the glass. Odd-shaped glass should not worry these as most use the frame edge to trigger a change in direction.

Frameless glass needs AI detection or a vacuum variance sensor.

 But remember that it cannot clean in corners, so you may have to do that manually.

Most Apps are just remote controls adding little if any, functionality to the WCR. A remote control helps stop and move the WCR.

Look for models with replaceable water tanks, flat plates, pads, and the sprayer nozzle. Most will have washable microfibre pads.

Winner: Look at better-known brands with good support.

Most should be fine on vertical framed or frameless glass, shower screens, tiles etc. But remember that the window cleaner solution probably will not cut through soap, shampoo and conditioner scum. As a rule, if you can easily remove the scum with a damp cloth and the WCR will work.

The cost-benefit is more about being prepared to live with any compromises.

We have experience with the Hobot 388 rotating pad type, and it is best on dirty windows. The Hobot 2S flat vibrating pad is best for windows in good condition. Both are about $500, so you need to use them a few times a year to get any ROI.

This guide will be updated with actual reviews of different brands and models over time.

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