Here's how we test the latest dishwashers.
It’s tricky to come up with tests for appliances like dishwashers.
The items used for a load need to be the same every time, have the same amounts of the same types of food on them, and there needs to be consistency in how many items you load into dishwashers of varying sizes. The problem is you can end up with a load that doesn't look anything like a real family’s.
How dishwasher manufacturers describe capacity doesn’t help either. You might have a 12-place-setting dishwasher, but when was the last time you threw a dinner party for 12 people? Or made dinner but didn't end up with any pots, pans or serving bowls to wash?
Our test uses items that most dishwashers deal with on a daily basis. There’s a steel pot and pan, a large serving dish, mugs, plastic plates, plastic bowls, a large glass bowl and plastic serving utensils. With all of this packed in, there’s only space in most full-sized models for 5 place settings – whatever the manufacturers claim about capacity. Where we used to fit 132 items in a 12-place setting dishwasher, we now have 82.
If a machine has an "auto" cycle, we select it over the "normal" cycle. We do this because an auto or sensing cycle should be designed to give optimum results for every wash. You're also generally paying extra for this feature. If there's no "auto" cycle we test on the "normal" cycle as this is what our members use the most.
We put each dishwasher through its paces at least twice and the scores are averaged.
To really test a dishwasher's ability to clean, we carefully dirty each test load with a range of foods and let them dry for 15 to 18 hours. And we’ve added baked-on porridge to the foods we’ve always used (such as baby cereal, spinach, egg yolk, tomato juice, tea and butter). Each of the foods plays a crucial part in assessing how the dishwasher performs and they’re there to test things like filtration, spray-arm effectiveness, rinsing and automatic sensors.
For water and energy rating labels, dishwashers are tested using a cycle chosen by the manufacturer. Any cycle can be used as long as it's stated in the instruction manual that it's designed to wash a normally soiled load at the machine's rated capacity. This means "economy" cycles can be used by manufacturers to minimise water and energy consumption, and so maximise the number of stars on the rating label.
Economy cycles often dispense with the drying part of the cycle. It saves on power, but means you may have to get out the tea towel.
Our test load also varies from the load used for water and energy rating label tests which doesn’t include items like pots and plastic ware.