You can't use the same heat-pump for heating the wash water and for drying. The water-heating heatpump would have to have a cold heatexchanger in the room air and a heat exchanger submerged\flowed by by water. And the heatpump would take an awefull long time to heat the water. Keep in mind, you need 4,2 kJ to heat 1l of water by 1k. Air only has about 1/4 of that.
The thing is, again, not that you could not put a heatpump into a standard sized 27" washer to make it a combo without modifying the cabinet. It is perfectly fine if you put it at the bottom of the machine.
The problem is that if you change the design of the cabinet of the washer, you would need a whole new production line. This would increase cost dramaticly.
Further, the price of such a unit would be closer to 3000$ rather that 2000$. Take the price of the full-sized LG combo, and than look at the price difference between the HybridCare dryer and a simmilar, standard dryer. Add that on top of the LG combo plus another few dollars because of it being harder to assamblem, and then you are doing real talk.
Going on, cycle time would be a major problem. One hour wash cycle for a 3/4 load. Ok so far. Now check how long the reviews on Amazon say the big LG combo needs to dry a load of laundry. Lets say, 3-4 hours. Now, as we saw, the heatpump technology takes about twice as long to dry a load of laundry. So one would end up with cycles of 6-8 hours, and that load wouldn't even be that big of a load.
Now, you could incorporate a traditional heater to speed up drying times. But this would push you to make it run at 240V, which again shrinks it target group dramaticly. (How many spaces do you know that only allow one 27" unit but have 240V service?)
In theory, everything is nice. But this will probably not happen anytime soon.
I find that particularly interesting as last I heard Japan was rather more 'green' than the U.S.
