Kärcher RVC 3 Comfort Extra

A brush that guides hair to the side instead of letting it wind around the shaft. It saves the cutting work in homes with long hair or pets.

How the mop is built: flat pads, two spinning discs or a roller. Discs press harder on dried-on dirt, a roller rinses itself while it works.

How much clean water the robot carries. It sets how long it mops before a refill, which a dock does by itself.

The dock empties the robot’s dust bin, usually after every run. You only empty the dock’s bag or bin.

The dock collects dust in a bin instead of a disposable bag. No bags to buy, but you empty it yourself.

The height of the dock. Mind a shelf or a window sill above it.

How the robot maps your home and follows that map. Lidar measures with a laser and works in the dark, a camera looks along and recognizes more.

The highest threshold the robot takes, as the maker states it. Measure your own: the step into a bathroom or onto a balcony is often higher.

How tall the robot is. It decides whether it fits under your sofa, bed or cabinet.

What the robot weighs. It counts most if you carry it up a staircase every day.

How much dust the robot holds before you empty it. It matters less with a self-emptying dock, which empties the bin after every run.

The noise in decibels, in the setting its source names: makers mostly give the standard setting, stores often the highest. 65 dB is like a vacuum at half power, 55 dB like a conversation.

The capacity of the battery. It hints at the runtime, but how much the robot draws counts just as much.

How long the robot cleans on one charge, at its quietest setting. After that it recharges and carries on where it stopped.