How we test dishwashers
By Yvette Fletcher
Discover how we test dishwashers to find the best models that leave plates squeaky clean and bone dry.
The video above shows how a Best Buy dishwasher can make a real, practical difference to you. We test every dishwasher in the Which? test lab using a strict range of criteria, and only recommend dishwashers that do an excellent job of cleaning and drying, and are easy to use and load.
Our reviews answer the most crucial questions about dishwashers, including:
- How well does the dishwasher clean away tough food grime from dishes?
- How easy is it to load and use?
- How much energy and water does it use?
- Is the dishwasher noisy?
- Should I buy it?
Compare which models come out top in our dishwashers reviews.
How well does the dishwasher clean?
To test how well each dishwasher cleans, we dirty dishes with milk, tea, minced meat, eggs, oat flakes, spinach and margarine, baking on these substances in a heated cabinet to ensure we give dishwashers a tough realistic test.
We even add in some clean dishes to the load, to see if the dishwasher spreads grime around the dishwasher - you wouldn’t want to buy a machine that just moves dirt from one plate to another.
After washing we inspect each item in the load and score the load for cleanliness and dryness. The best dishwashers leave every item spotless and dry, while the worst deliver you dirty wet dishes.
In October 2018 we made how we score each dishwasher's cleaning and drying tougher. This is because dishwashers have gotten better over the years of regular testing we do, and we want our recommendations to still be the best for you.
How easy is it to load and use?
Our dishwasher testing load includes a saucepan, glass jug and plastic lunch box
We load dishwashers with a typical load of dishes, including dinner plates, soup plates, dessert plates, cups, saucers, knives, forks, soup spoons, tea spoons, serving bowls, a serving fork, a ladle, a saucepan, a shallow dish, a glass jug and a plastic lunch box.
We assess how easy it is to fill and empty each dishwasher up to capacity, and whether it can accommodate large plates and long-stemmed wine glasses. We've found that some smaller slimline and table-top dishwashers can be harder to fill to capacity than their larger counterparts, but some full-sized models are very tricky to load, too.
We read all of the instruction booklets that come with each dishwasher, and assess how clear and easy to understand they are. Clear, well-labelled controls that make programming easy get the thumbs up from us. And because a good dishwasher is only great if it's effortless to use, we also check how easy it is to open and close the door, refill the salt and top up the rinse aid. We also remove and replace the filter to see how straightforward this is.
How much energy and water does it use?
Each dishwasher has a main program that tends to clean at about 55-65°C and is the most suitable for an everyday load of dishes. Where there isn’t a main program, we test the automatic program which self-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 test the cleaning and drying power of the main programme on every dishwasher we assess, as well as measuring its water and energy use.
We also test the energy-save or 'eco' program for its energy and water use and provide running costs for each model so you know how much each dishwasher will affect your utility bills.
How noisy is the dishwasher?
Dishwashers don't tend to be as loud as other appliances such as vacuums, but a quieter model is an important consideration for those whose dishwasher sits in earshot of areas where people eat or relax, and also for those of us who like to run the dishwasher over night.
We assess how noisy the filling and washing stages of each dishwasher are, listening out for any loud or particularly irritating noises or tones.
Should I buy it?
Each of the assessments described above goes part way to making up a total test score, which is the overall percentage figure we award to each dishwasher.
But certain assessments are more important than others and so carry different weights. We think the most important job of a dishwasher is to get your dishes both clean and dry, so a large proportion of our test score is based on this. The score is broken down as follows:
- 60% cleaning and drying
- 20% energy and water use
- 15% ease of use
- 5% noise
A full-sized dishwasher needs 75% in our tests to earn our Best Buy recommendation. Slimline and compact dishwashers need 65%. Dishwashers that score 45% or less are highlighted as Don't Buy models to avoid.
More than 50 years of dishwasher testing
Front-loading dishwashers as we know them now first entered our kitchens back in the early 1960s. By the end of the 70s dishwashers were one of the most common home appliances. The Colston Mk4 was the first to become a Which? Best Buy in 1965.
Now each year we test over 70 different machines by cleaning a whopping 25,000 dishes, bowls, cups, glasses and pieces of cutlery.