[robnado]

Combining refrigerator, water heater and heat pump implies the need for transferring the fluid used as refrigerant between these components. This is usually a gas that is not trivial to contain, so creating this shared pipeline increases the points of failure. Further, you now have to insulate the entire length of this system, using material to do so, and you will end up losing a certain amount of efficiency anyways in this piping system. Also, what if your need in hot water is much greater than your need to cool the house or vice versa, what is your backup system for disposing of heat or cold when not required? It’s not certain that after solving all these problems and others, that you still have a net efficiency gain.

[nanomonkey]

I think you could get away with two insulated reservoirs (frozen and hot water) and then use something like glycol, alcohol or water to shuttle hot and cold to your shower, under floor heating/cooling. Frozen water can be mechanically stirred (like a slushy machine) to keep it from freezing solid, allowing you to pump it through pipes. Water can also be mixed with salts or alcohol to alter it's freezing temperatures, with allow you to move cold from your freezer to the refrigerated areas (fridge, computers or living spaces). You can also use air as a working fluid. Any excess can be dumped to the outside environment with a radiator as a last resort.

Modern cars are already doing this with heat pumps to manage batteries and the cabin temperatures.

It's pretty easy to see where building technologies will go by looking at car technologies...

[alanbernstein]

I like to imagine a world where it's acceptable for houses to be designed around a utility room where all of these interchanges, insulation, isolation, exhaust, issues can be contained, and accessed, in a small, separate, space that is not part of the living area.

[Etheryte]

Unfortunately it's also a world where having a problem with your aircon means your fridge stops working and replacing a fridge means calling in a technician for the plumbing.