The overall Which? test score is made up of the following star ratings, all determined by our rigorous lab tests.
How we test mud on carpet
We test how well each carpet cleaner cleans a dried-in mud stain.
How we test deep refresh
How well each carpet washer or multi-function wet and dry cleaner performs on its core function of washing a carpet using water and detergent. A carpet cleaner with five stars for carpet washing will leave carpets clean and refreshed, a one star machine will do little more than wet the carpet.
How we test drying carpets
We record how long carpets take to dry after being washed. A five star carpet cleaner sucks up enough water to allow you to walk on the carpet after about two hours. A one star machine has much less powerful suction and will leave your carpets much wetter for much longer.
How we test stain removal
We test carpet cleaners against dried on coffee, wine and gravy. It's a struggle for most machines against tough stains like this, but the best will at least reduce the mark the stain leaves. One star carpet cleaners will have little or no effect on the stain.
How we test walls and corners
You want a carpet that's cleaned right to the wall and that's why we test for this - we record how close the carpet cleaner gets to the wall to give you an idea of how much of your carpet will be cleaned. A five star machine will be almost flush to the skirting board whereas a one star machine will be a centimetre or two away, leaving an untouched border to your carpet.
How we test quietness when cleaning
We record how noisy the carpet cleaners are while being used. A five star machine will be noticeably quieter than a one star machine - it will be possible to have a conversation while a five star machine is working, but you'd struggle to hear yourself speak with a one star carpet cleaner.
How we test ease of use
A one star carpet cleaner will be much more difficult to use than a five star machine. This could be because the water tank is hard to remove, the detergent dispenser is hard to fill or the mains cord isn't long enough. Your life will be made much easier with a carpet cleaner scoring four or five stars for ease of use.