The cost/invasiveness of cutover is dropping. There is a relatively new category called "plug in solar" where the inverter/battery is smart enought to detect, sync and use grid power.

The Stream system: Connect the device to the grid to enable it to feed power into the grid or draw power from it when solar energy is insufficient. This can be done via a standard home outlet (if permitted), or through a circuit breaker. [0]

0. https://manuals.ecoflow.com/us/product/stream-ultra?lang=en_...