I would think you'd want one central hub to effectively control the whole home. That makes sense to me. Like a thin UI wrapper to control EVERYTHING displayed on an LCD panel... in the living room(?). This makes sense because your selling point is a turn-key home. It would stand to reason that if the hardware is turn-key, the software should be too.

Bringing this all under one central control hub would probably take an equal stakeholder in your business. It's just as important as the material aspect of the home. If you don't have the wherewithal for this, you should probably avoid doing ANY kind of fancy electronic stuff. I know the PV panels are a non-negotiable... but I would suggest not going beyond that until you can create an SDK. This manages expectations, and paves a sane "upgrade" path for the hardware. Simple is always better than fancy.

I'm not interested in buying a home. If only I had the money. I assumed you had an official SDK, but it sounds like you guys are still in the stage of wrangling several pre-existing technologies/solutions out there.