So why cant she connect the panels to her own circuit and thereby use less utility wattage? If she did, would she have to reimburse somebody for a subsidy?
Batteries are the tool needed to compensate for the wide fluctuation in solar output. If the house is using 5kw and the solar is at 5 kw output, perfect. But cloud comes over, solar drops to 1kw, house load cannot be turned off that fast.
Then cloud passes and solar jumps to 8kw. House can find or turn on loads fast enough.
It is the hybrid inverter that with the aid of a battery bank that ‘blends’ the variations together. When cloud comes over house takes energy from batteries, and when solar goes higher than house loads, the batteries are instantly sucking in the excess energy. Battery can track the energy variation from solar in realtime, the house loads cannot.
In a grid tie situation the utility does the realtime give and take processes.