There are two solutions to energy storage. First is to charge batteries with the generated power. The advantage is that the charged batteries can provide power even during night time. This is simpler to design and most components to charge the battery and convert the power back to AC-electricity are readily available. The main issue is cost of buying and maintaining batteries specially for large storage systems. Also the big battery banks require significant storage space.
Second solution is to feed the generated power back to Grid. Grid is the electric network, like that of PG&E, that supplies power to our homes and offices. This reduces the installation and maintenance cost associated with storage batteries. However it adds to complexity of system design and associated components.
This solution relies on the concept of "net meeting". In the USA, as part of the Energy Policy Act of 2005, al lpublic electric utilities are required to provide net metering to it's customers.
‘‘NET METERING.—Each electric utility shall make available upon request net metering service to any electric consumer that the electric utility serves. For purposes of this paragraph, the term ‘net metering service’ means service to an electric consumer under which electric energy generated by that electric consumer from an eligible on-site generating facility and delivered to the local distribution facilities may be used to offset electric energy provided by the electric utility to the electric consumer during the applicable billing period."
There are limits to which utility companies agreed to buying back power from consumers since it in effect reduces their revenue. The legislators are working on increasing the limits to allow for wider Solar PV adoption.
On the technology aspect of feeding back power to grid, the Inverter has to do the heavy lifting. Also since the power is being fed back to the grid, there are several regulations that govern the power quality and safety standards.
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