Restaurant dishwashers use an enormous amount of water. They require a hot water supply that’s much hotter than residential heaters typically supply. They require a more complete manual pre-rinse and scrub. They only accept kitchenware that’s made for them and destroy the rest.

Restaurants cycle dishes a lot during a single mealtime. Homes don’t. I don’t think “I can’t wait 2 hours” is typically a real problem.

> I've always been wondering why they don't exist on smaller scale.

Because they need space, they need even more nasty chemicals than domestic dishwashers, they need a stack of trays to load the dishes on and a crew to load and unload them.

If you want a dishwasher which doesn't require unloading after use you can get 2 of them, one of which is "clean", the other "dirty" or washing. When the "dirty" one is full you turn it on and let it wash while you take whatever you need from the "clean" one. Once the formerly-dirty one has finished it's cycle the roles are reversed and it becomes the "clean" one.

That's called a Hobart. https://www.hobartcorp.com/products/commercial-dishwashers

I've used these while working as a volunteer in a camp kitchen during work weekends, where we had maybe 20-40 guests eating a meal. You put dishes/silverware/pots/pans/whatever in a square tray, push it into one side of the Hobart, and pull down a lever to close the doors and start the cycle. They take a number of minutes that you can count on one hand... I seem to remember 90-120 seconds but I'm not sure. Stuff comes out clean and hot on the other side, and you want to pipeline this so it's one person with dirty hands feeding stuff in, and one person with clean hands (and thick gloves) pulling the square trays out, letting them cool, and putting the clean dishes/etc. away.

They release a huge amount of steam and they're wonderful for this kind of volume (20-40 people at a meal + all the cooking implements to support this). Larger than home use, though --- unless of course you had a mansion with servants. And I get the sense that maintenance and operating costs would be a lot higher than a regular plain dishwasher.

I've dreamed of a dishwasher for people who prioritize clean dishes quickly and quietly over the incremental savings from using asymptotically less water or energy. See also low flush toilets and clothes washing machines.

I've long dreamed of a dishwasher that can detect when you remove the (cleaned) dishes from it, and presents a display saying 'load dishes' or something like that. And after finishing a cycle, says 'unload dishes'. Should be pretty easy to achieve with some load cells in the feet, but haven't seen any like that.

I don't know the first thing about dishwashers, but it seems obvious to me.

The cycle-to-volume ratio is as bad as it could possibly be. Conventional dishwashers recirculate water as they wash and rinse. I imagine there's an mx + c formula to how much water is needed (c = enough water to prime the pump or whatever). So compared to a normal size load, you'd be wasting that constant amount of water.

The wash is also likely going to follow mx+c (c = time for grease to break down, time to rinse, time to dry etc). You can wait a few hours for a whole set of crockery. Can you wait a few hours for a single plate?

Commercial "passthrough" dishwashers work very differently. Manual mechanical action with a spray, plus a quick wash, sterilise and rinse. At that point why not wash your single plate by hand?

What you really want is 2 dishwashers! That way you never have to unload the dishwasher because you alternate your dishes between the two. The one that has just completed the cleaning cycle has now become a cupboard with the clean dishes and the other one becomes the dirty dish storage and vice versa.

It can be accurately simulated with appropriate brushes and rags, water and soap, and a sufficient number of hands.

The answer is obviously paper plates and plastic silverware /s