I think there are probably some gains to be made in whole-system design in houses, for energy efficiency. After all, we have one device to pump heat out of a small box and into the air (fridge), a different box to pump heat from the inside to the outside (air conditioner) and then a tank to put heat into water (water heater). I have a feeling that all of these heat pumps could be connected for greater efficiency somehow.
Mokalus of Borg
PS - I'd be surprised if that were the only gain to make.
PPS - A good architect probably designs this kind of system all the time.