One of the problems is that storage inefficiency is already built-in to most new PV installations. Well over half of new installations are based on grid-phase-s

One of the problems is that storage inefficiency is already built-in to most new PV installations. Well over half of new installations are based on grid-phase-sync microinverters. Adding storage to the system involves adding rectification and re-inversion losses. If solar installers would default to building out DC -> primary inverter systems, then adding storage would be much less lossy. But as it is, economics drives the industry to strongly prefer microinverters.