With prices for a robot vacuum cleaner ranging from £300 to £800, it's not a product you want to be taking a speculative punt on. From the Dyson 360 Eye to the iRobot Roomba 980, we've tested the very latest models to find out if they are really worth their hefty price tag.
Below we reveal just how far we go to find the best robot vacuum cleaners, including using our specially built robot vacuum cleaner testing room to test how good each robot is at avoiding common household obstacles.
We can answer all of your questions, including:
You can't tell in a shop how well a robot vacuum cleaner will actually clean, which is where our tests come in.
We spread super fine Arizona sand over thick Wilton carpet, and spread chunky lentils over a hard floor to test how effectively each robot can pick up mess from different surfaces. We wait until the robot is finished and returns to its charging station and then measure how much they managed to pick up.
We also comb pet hair into thick carpet and challenge each robot to suck it up.
Even the best robot vacuum cleaners can't clean as thoroughly as a standard vacuum cleaner. For example our best robot vacuum sucks up about 50% of the dust that we embed into carpets, whereas the best standard vacuum cleaner we've tested can suck up 86%. But a good robot will keep your home cleaner so you have to get your main vacuum out less often.
To make sure you don't get left with uncleaned patches of floor, or a helplessly stranded robot, we built a specially designed room complete with tables, chairs, lamps, rugs and low hanging curtains to see how well each robot gets on navigating around a typical room.
We have cameras in the room and sensors in three places on each robot so that we can see exactly what spots the robot covers and the areas it fails to reach. The best robot vacuum cleaners cover 15% more floor surface than the worst.
Some cover the floor systematically and quickly, whereas others randomly bounce around the room and take much longer. The quickest cleaner takes only 23 minutes to clean our room, whereas the worst takes two hours.
As part of our testing we not only find out exactly how high a ridge each robot vacuum can climb over - so you know if your door thresholds will prove a climb too far - we also put a wide array of everyday obstacles in the path of each robot and see how they handle it.
Our robot test room has a tangle of wires, tables and chairs, a domed floor lamp and fold out chairs in it to try and trip up each robot cleaner. The best can navigate all of these obstacles with no trouble and return to their charging base when done. The worst trip up on an obstacle each and every time and need constant human intervention to get back to their base for recharging.
We rate how easy the robot is to get started out of the box, how easy it is to programme and schedule and also how easy or difficult it is to do regular maintenance on your robot, such as emptying the dust container and cleaning any filters.
Some robot vacuums come with a remote control so that you can turn it on and even schedule it without moving from the sofa. Others, such as the Dyson 360 Eye and iRobot Roomba 980, have an app that lets you control the robot through your smartphone or tablet. These apps will often show you exactly where the robot has been while it is cleaning and are a great tool for checking up on your cleaning even when you aren't at home.
All of the tests described above feed into the total test score for each robot cleaner. Certain assessments, such as cleaning ability, are more important than others and so carry more weight. Our overall ratings for robot vacuums ignore price and are based on:
A robot vacuum cleaner needs to score 72% in our tests to earn our Best Buy recommendation. Robot vacuum cleaners that score 40% or less are named as Don't Buys because we believe they are too poor at their main job to be worth buying.
Lithium-ion batteries always deplete and eventually die over time, and at Which?, we believe that cordless products should last longer than the batteries they come with. That's why we no longer give robot vacuum cleaners Best Buys if spare batteries cannot be bought from the manufacturer – no matter how good the robot vac might be.