Our in-depth testing has found that dishwashers are, on average, four times more water efficient than washing by hand per place setting.
The most water-efficient full-sized dishwasher uses almost 10 times less water to wash the same amount of dishes as hand washing them.
Find out how much water it takes to wash up a meal for two, what our testing shows and how the energy use compares between using a dishwasher and washing in your kitchen sink.
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Dishwashers vs hand washing
Plate for plate and glass for glass, full-sized dishwashers are more efficient than their slimline counterparts. This is because you can wash more dishes in them with only a little bit more water used.
However, even if you were to use the most thirsty slimline model available, it would still use half the water that hand washing does.
| Method of washing | Best (litres) | Average (litres) | Worst (litres) |
|---|---|---|---|
|
Full-sized dishwasher
|
1 | 2.2 | 4.2 |
| Slimline dishwasher | 1.8 | 2.7 | 4 |
| Handwashing | n/a | 9 | n/a |
Read our dishwasher reviews to find out which match fantastic energy and water-efficiency with brilliant cleaning and drying.
What our dishwasher testing shows
When washing up, we estimate that you can wash around two standard meal sets with one washing-up bowl (average capacity of nine litres) before you would need to empty the water and fill it again.
One standard meal set is equivalent to one place setting in a dishwasher: one dinner plate, dessert plate, soup plate, glass, saucer, cup and set of cutlery.
However, dishwashers don't just wash one or two place settings at a time; some can wash up to 16 in one wash. To make it an even comparison, we filled a dishwasher up to the maximum before putting it on.
We then divided the water used in one wash by enough to just wash two place settings - one washing-up bowl. Doing this, we can get an even comparison.
We found that all dishwashers, even the least water-efficient, can wash twice as many dishes using the same water.
- 19 sets - Best dishwasher
- 9 sets - Average full-sized
- 7 sets - Average slimline
- 4 sets - Worst dishwasher
- 2 sets - Hand washing
This is based on all the dishwashers we've tested in the past 10 years.
What about energy use?
Dishwashers on average use about 1.12kWh of energy per wash. This costs roughly 38p, based on 34p per kWh, although that will of course depend on your energy provider.
How much energy used to heat up water for your washing up bowl will depend on the heater.
If you have a gas-heated water tank, it isn't an easy comparison (a bit like apples and pears).
Gas is typically cheaper than electricity, but is worse for the environment.
If using an electric immersion heater that's 3kW, it will cost roughly 16p to heat up a nine-litre washing up bowl*.
As dishwashers are able to wash more in a single wash, using less water (and hence having less to heat up), they could be more energy-efficient too.
* Based on a unit of electricity cost of 34p per kWh (October 2022 price guarantee).
Want to know more? Read our guide to dishwasher energy running costs to find the most efficient dishwasher for your home.
undefinedsource https://www.which.co.uk/news/article/which-research-reveals-how-little-water-dishwashers-use-compared-to-hand-washing-aUDng9Y2iK8E