Dreame D20 Air Plus

Suction in pascal, as the maker measures it. More pascal helps on carpet, but it says little about how well the robot picks grit off a hard floor.

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.

The side brush swings out in a corner or along a baseboard, so the dust there is swept in too. On this model: the maker names this feature nowhere on the product page, so we take it as no.

The robot notices when it drives onto a carpet. Most then raise their suction, and a mopping robot lifts its mop or leaves it at the dock.

Whether the robot copes with pet hair: a brush that hair does not wind around and a dock that empties the bin for you. Where the maker does not say so itself, we read it from those two.

A sensor notices where more dirt lies, at the doormat for example, and the robot cleans that patch longer or a second time.

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.

The pad slides out along a wall or a baseboard, so the last few inches are mopped as well.

The robot leaves the mop at the dock before it vacuums a carpet, so the carpet never gets wet. On this model: the maker names this feature nowhere on the product page, so we take it as no.

The robot returns to the dock during a run to rinse the mop, instead of pushing dirty water around.

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. On this model: the bag sits in the station.

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

How much the dust bag in the dock holds.

How long the maker says a dust bag lasts with daily use. With pets or a lot of carpet it is shorter.

The dock mixes detergent into the water itself, from its own bottle. On this model: the maker names this feature nowhere on the product page, so we take it as no.

The dock can be connected to the tap and the drain, so you never fill or empty a tank. It does need a connection nearby. On this model: the maker names this feature nowhere on the product page, so we take it as no.

The clean water tank in the dock, which wets the mop. On this model: from the maker's product text, not from a specification table.

The width of the dock.

The depth of the dock, measured from the wall.

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. On this model: from the maker's product text, not from a specification table.

How the robot sees loose things on the floor, such as cables, socks or a pet accident. A camera with depth sensing sees more than a bumper that reacts on contact.

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.

An extending leg or wheel that carries the robot over a high threshold. Without one it usually stops at about 0.8 in (2 cm). On this model: the maker names this feature nowhere on the product page, so we take it as no.

How you keep the robot out of a place: a zone you draw in the app, a virtual wall or a magnetic strip on the floor.

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

How wide the robot is. Narrower gets between chair legs more easily, wider usually means a bigger dust bin.

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 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. On this model: from the maker's product text, not from a specification table.

How long an empty battery takes to charge fully in the dock.

Matter is the standard that lets devices from different makers work together. With it you can run the robot outside the maker’s own app. On this model: the maker names this feature nowhere on the product page, so we take it as no.

Which voice assistants the robot works with, such as Google Assistant or Alexa. On this model: from the maker's product text, not from a specification table.

The warranty the maker gives in the United States.