If you expect your solar panels to power your house when the grid goes down, make sure you check that. They most likely will not, unless you've added a battery and switches.
The battery is largely optional. The critical bits are the switch, aka “microgrid interconnection device”, and the inverter’s ability to make a decent sine wave without grid assistance.
Only kind of. Without a battery your power will go out every time a cloud covers the sun, unless you have a hugely oversized array.