What a robot vacuum dock does, job by job

How each job works

Charging is the one thing every dock does. The robot drives itself home when the battery runs low or the cleaning is finished. A dock that only charges is small enough to sit against the skirting board and be forgotten. A bigger dock can take on up to five jobs as well.

Emptying the bin is the first of them. A robot is a low, flat thing, so the bin inside it is small, and on its own it needs tipping out often. A self-emptying dock has a second fan and a much bigger container. When the robot parks, the dock pulls the dust out of the robot’s bin through a port and into its own, which makes it, more or less, a vacuum for the vacuum. On many docks the container is a disposable bag, and on others it’s a bagless bin that you tip into the rubbish yourself.

Washing the mop is the second. In our list, every dock that does it belongs to a robot with spinning pads or a roller. The robot parks over a tray, the dock runs water across the mop while it turns against a ribbed plate or a scraper, and the dirty water is pumped up into a tank. Many robots go back for a rinse partway through a clean, so the lounge isn’t mopped with what came off the kitchen floor.

Drying is the third, and it comes straight after washing. The dock blows air over the mop, often warm air, for a few hours. It matters, because a wet mop shut inside a dock is how a robot comes to smell like a forgotten dishcloth.

Refilling is the fourth. The dock has a large clean-water tank and tops up the robot from it, so the robot can mop the whole house without you filling anything in the middle.

Adding detergent is the fifth. Some docks hold their own supply of it and add it to the mop water for you.

What the name on the box does and doesn’t tell you

Docks have grand names. You’ll see “Omni”, “Ultra”, “all-in-one” and “station”, and none of these has a fixed meaning. Read past the name and tick the five jobs off one by one: emptying, washing, drying, refilling and detergent. Every robot page on this site lists them that way.

Even a full tick-sheet leaves some things out. It doesn’t say whether the mop is washed in hot water or cold, or dried with warm air or air at room temperature. Those details change how well a greasy mop comes clean and how quickly it dries. It doesn’t say how big the two water tanks are, which sets how often you’ll be carrying them to the laundry. And it doesn’t say how big the dock itself is.

“Self-emptying” needs a careful reading too. The dust still has to leave the house eventually, and what the dock really does is turn a small job you do often into a slightly bigger one you do far less often.

What’s left for you

With a full dock, the remaining chores are short and fairly regular:

• Fill the clean-water tank and tip out the dirty one. The dirty one is better done promptly, since old mop water smells.
• Change the dust bag, or empty the bagless bin, when it’s full.
• Rinse the tray the mop is washed in, which collects sludge over time.

With a dock that only charges, you empty the robot’s bin yourself and wash the mop pad by hand. That suits plenty of people, and it only becomes a nuisance when you’d hoped to leave the robot alone for a fortnight.

How it plays out in a real house

Start with where the thing will live. A full dock is closer to a small piece of furniture than to a charger. It wants a spot against a wall, within reach of a power point, with clear floor in front for the robot to drive in and out. Many have a ramp at the front that adds to the depth. A hard floor is the sensible place for it, given that water is going in and out. Measure the spot before you buy.

Then there’s the noise. Emptying the bin is usually the loudest thing the whole machine does. It’s a short roar that lasts some seconds, and it happens when the robot gets home, which may be while you’re on a call in the next room. Many apps have a do-not-disturb setting that makes the dock hold off.

Pets are a good reason to pay for self-emptying. A dog that sheds can fill a robot’s small bin in a single run, and a robot with a full bin picks up less and less. With a bigger container at the dock, the robot can keep going out every day through the worst of the shedding.

In a small flat there’s less floor, so the little bin lasts longer between empties, and less wall to give up to a station. A charging dock tucked beside a bookshelf can be the better fit.

Which jobs to pay for

Start with what would annoy you. If you know you’d forget to empty a small bin, pay for self-emptying, and that goes double if you have pets. If the robot is going to mop, a dock that washes and dries the mop is what keeps you using the mop at all. The alternative is handling a wet, dirty pad after every run. If the robot only vacuums, the washing jobs are money spent on nothing.

Then check the fit: the size of the dock against the spot you measured, and the water tanks against how far you’re prepared to carry them. The “In our list” box on this page counts how many docks do each job. The Robot Matcher also asks how much of the work you want to do yourself.