Dishwashers: How we test dishwashers

How we decide which dishwashers to test

Which? tests the best-selling dishwashers and we also look for newly launched or interesting machines, particularly if they have innovative features, programs or design.

What makes a Best Buy?

Check out our video to see why a Best Buy will make a real, practical difference to you.

Washing dirty dishes - the ‘Egg and Spinach’ test

Dishes are soiled with spinach, eggs and oat flakes

We dirty the dishes with milk, tea, minced meat, eggs, oat flakes, spinach and margarine. Some items are loaded clean – this shows us how the soils spread around the dishwasher; you wouldn’t want to buy a machine that just moves food waste from one plate to another. Once we've covered the dishes in food, we dry the soils onto them in a heated cabinet.

Loading dishwashers

We load dishwashers with a typical consumer load of dishes, cutlery and other everyday kitchen items. Our test includes dinner plates, soup plates, dessert plates, cups, saucers, knives, forks, soup spoons, tea spoons, platters, serving bowls, a serving fork, a ladle, a saucepan, a shallow dish, a glass jug and a plastic lunch-box.

Dishwasher program testing

We test the main program for dishwashing, energy and water use

We test the dishwashing, energy consumption and water use of the main program – this is the one most suitable for an everyday load of dishes and usually washes at around 55-65°C. Where there isn’t a normal program, we test the automatic program which selects the wash-temperature, duration and energy and water-use. If a dishwasher has both, we select the one that's likely to be used most often. We also test the energy-save program for energy and water use.

Dishwasher self-cleaning

We spread jam over the inside of the dishwasher door, leave it to dry and then run the main program with a full unsoiled load. We check how clean the door is after the program and note whether any jam has been transferred onto the plates.

Ease of use assessment

We read all of the instruction booklets that come with each dishwasher and assess how clear and easy to understand they are.You can change the height of the top basket on most machines, but some make it much easier by using quick-release clips, so we look for this on each machine, too.

We rate how easy each dishwasher is to load and unload and we look for clear, well-labelled controls that make programming easy. We check how easy it is to open and close the door and to re-fill the salt and rinse-aid. We also remove and replace the filter to see how straightforward this task is.

Dishwasher noise

We measure how noisy the filling and washing stages of each dishwasher are, and we subjectively assess the sound of the dishwasher while in use, listening out for any loud or irritating noises or tones.

Dishwasher build quality

We inspect the build quality of each dishwasher and look for a solid feel with strong joints and seams. We also look at how well the controls and other parts have been fitted.

Which? dishwasher testing methods

Some dishwashers in our online review have a note showing that they were tested with a full-load placed in the dishwasher according to the standard test load pattern of the manufacturer. This was our previous way of testing dishwashers - we've changed the way we load the dishwashers for our lab tests 2010.

Though you can generally compare older results with the latest dishwashers we’ve tested, the results don’t directly correspond. However, each score still gives a very good indication of the overall performance of the dishwasher.

We test the dishwashing performance, energy consumption and water use of the main program. We also test the energy and water consumption of the energy-save program. Older machines also had the wash performance of the energy-save program tested as well, which is why you’ll find star ratings online for some machines.

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