This article by Which? suggests that even the least water-efficient dishwasher still only uses half the amount of water compared to washing by hand. Dishwashers could be more energy efficient as well. Read more here:
https://www.which.co.uk/news/article/which-research-reveals-how-little-water-dishwashers-use-compared-to-hand-washing-aUDng9Y2iK8E