My focus lately has been backup power. Maybe a solar or auto transfer battery bank built specifically for reef aquariums. Something that will switch from grid to battery, in a power outage, but also run the entire system more efficiently, during off peak.
Not for backup for me, but a low-voltage (48V) DC-only peak load shedding system is pretty compelling. I run a solar system, but didn't do a whole-house battery due to ROI and complications, but the ROI on a tank-only system for lights/pumps would actually make sense.