There's not enough heat in the fridge to heat up any significant amount of water.
I would however like to see that waste heat being used for something like dishwashers or just being vented out (instead of into the room that might have to be actively cooled).
No it's not. Claiming heat from a fridge would be like grabbing a cup of water for a minute a few times a day. The extra shit that needs to be manufactured and transported is surely not worth the effort at all.
Mini-split HVAC systems create both heated and cooled air, and send them to just the rooms they are needed, while also redistributing existing disparities of hot and cold. The latter being the most efficient HVAC mode of all.
I could imagine at some point, all our heated and cooled air, water, and ice could be one system.
For fast temperature demands, such as hot water or ice, perhaps reservoirs of chemically stored heat and cold could be built up at useful locations, for very high speed release when needed.
Completely dispense with storing hot or cold air/water, except for fridges. But provide the cool air for them, as a byproduct of being one system, avoiding the local inefficiency of both cooling air in small quantities and generating heat at the same location.
It would make it cheaper to have more fridges and ice makers around a houses, if you just had to plug them into power and an HVAC controlled "inlet/outlet".
Correct! This is how some advanced systems already work in multifamily, where one room's excess heat is routed to another rooms lack of heat -- "Variable Refrigerant Flow" or VRF
I wouldn’t be surprised if someone starts making these. The heat that comes off a typical refrigerator is enough to heat about 1/3 of a typical house’s hot water usage.
Sorry, didn't see any "kitchen fridge/hot water tank combo units" on their website. Care to provide a link?
Or perhaps you may have missed a nuance in the comments above yours? Nobody is claiming that heat pumps don't work, they certainly require a source of heat to pump though, and the air in a kitchen fridge ain't that.
I would however like to see that waste heat being used for something like dishwashers or just being vented out (instead of into the room that might have to be actively cooled).