A nice, clean battery-system add-in for existing grid-connected PV systems would be really nice.
Most seem to be very expensive controllers, without even considering the cost of the batteries or a real Battery Management System.
With most grid-connected PV systems, if the grid fails, the home loses all power, even when the PV system could be producing sufficient power.
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle