An AC coupled system is a system that uses an off grid, battery based inverter to power a load, and uses a grid tied inverter to also power that load. The grid-tied inverter will tie to the output of the off grid inverter, provided its output is within the NEC spec for voltage, frequency, and phase.
The advantage to this setup is that in the daytime you can power a load directly from two power sources, and you have the batteries as a buffer to assist for any surge current needed.
Also, the solar power is inverted immediately using an Enphase AC solar panel which has an electrical conversion efficiency of nearly 98% as opposed to charging the batteries first at en efficiency of about 80%. For more information please email me at [email protected]