In addition, a dishwasher has high pressure pumps, a centrifugal grinder, and its own water heater (to heat hotter and more localized than a central water heater, above sanitizing levels)
* You don't need rinse water, so the total water needed is at least halved. Since the water is just sitting in a bucket, you can do many, many washings with the same water which increases that efficiency even more.
* You don't need heated water as sanitation and complete cleanliness is unimportant. Heating the water alone uses more energy than everything else put together.
* You don't need particularly clean water, just clean enough to prevent large dirt from adhering. As such you could use floor-cleaning chemicals that clump the dirt and precipitate it to the bottom increasing use time. Reusing water and the chemicals in that water for longer has a very large impact on the environment.
* a couple strokes with a bottle brush take way less energy than a high-pressure pump and once again, get the item clean enough.
* Fewer things going through your dishwasher increases its lifespan and decreases the total cost of operation. This is also better for the environment
A dishwasher is more efficient than hand washing under normal circumstances (not an ancient dishwasher, not pre-washing dishes, more than one plate to wash, etc).[1][2][3][4][5][6][7][8]
Edit: added citations and removed "IIRC"
[1] https://www.pcrichard.com/library/blogArticle/why-dishwasher...
[2] https://www.reviewed.com/dishwashers/features/please-stop-ha...
[3] https://www.treehugger.com/kitchen-design/built-in-dishwashe...
[4]https://www.realsimple.com/home-organizing/cleaning/more-tec...
[5] https://www.cnet.com/how-to/how-much-water-do-dishwashers-us...
[6] https://www.npr.org/sections/thesalt/2017/11/24/564055953/to...
[7] https://www.huffpost.com/entry/wash-dishes_n_7232216?guccoun...
[8] https://www.energystar.gov/products/appliances/dishwashers/d...