What are the downsides of robot vacuums?

A robot vacuum is one of those quality-of-life improvements that, on paper, should save you time. You're able to set it up and, once it's mapped your floor space, it can be left to do the job for you. Some robot vacuum cleaners can even empty their own dustbin and, if you've got hard floors, mop it clean of any built-in grime, too.

That all sounds great: who can argue with less chores for themselves? The only problem is that a robot vacuum isn't a like-for-like replacement for a human cleaner. There are plenty of disadvantages to using a robot vacuum, from obstacles to missed spots it can't quite reach. Buying an upgraded model isn't a catch-all solution, either.

There's plenty to love about robot vacuums, but these are some of the points you'll need to consider before you hang your upright for good.

A human cleaner has a really big advantage over a vacuum: it can move things out of the way. That doesn't seem like a huge problem, but the vast majority of robot vacuums lack arms. It can't just move a chair or get a hoover nozzle into a tight spot to clean up dust. There's also the unknowns to think about that it won't have mapped on its route, like toys, charging cables left trailing across the floor or even pet messes that can be spread around the house.

That's not to say that robot vacuums can't overcome some of the issues. By design, even basic robot vacuum cleaners will change direction or move aside if they encounter an obstacle, rather than just following their pre-planned route. The cheapest models will use bump sensors, so it'll need to physically collide with something. That can leave it going over the same patch again and again when it runs into a barrier. The best robot vacuum cleaners may use infrared sensors to try and bypass this, with the most expensive relying on LiDAR sensors and AI cameras to work out its surroundings better.

Yes, more expensive models will have more freedom to navigate as they can identify more problems to work around. That said, even the most complex models can't deal with some obstacles, at least very well. Loose cables are a good example: they can wrap around brushes or wheels and stop the vacuum in its tracks before it completes a run. Socks are another problem that can get sucked in, as can lightweight rugs, unless you have a model like the Roborock Saros Z70 that can move things out of the way. While robot vacuum cleaners are more independent, you're still going to need to check your floors beforehand, just to make sure that it won't run into a problem that it can't ride around.

What type of dirt are you expecting to clear up? A robot vacuum is versatile, but it's not infallible, and it's not the ideal tool for some environments. Picking up crumbs from a wooden floor is certainly in its wheelhouse, but pulling out dirt from a thick carpet is a much harder job. Cleaning up surface debris is where you'll see the best results.

You'll notice, if you use a traditional vacuum cleaner, that the best models feature a powered floorhead that can agitate and lift up dirt that's been engrained in carpet fibres. You're able to move back and forth to get the dirt out. How well a robot vacuum is able to do this itself will depend on its brush design, but the advertised suction figure won't give you a clear idea of how well it cleans.