They use loads of water!!! Anywhere between 15 (56,8 l) and 7,5 (28,4 l)gallons! That's huge!
My BOL dishwasher does a great job with 18 litres (4,7 gal) and that is quite a lot. New Ariston machines work with only 13 litres (3,4 gal).
But I must say that here the longest cycle is only 108 minutes, the normal being 67 minutes. On mine it takes twice that much for the same, normal, cycle.