The new Tesla installation in Southern Australia is 100MW. I don't know the specifics, but the combined battery capacity of the two big Southern California utilities is at least 120MW, including one 80MW installation (also by Tesla). The three big CA utilities are mandated by law to have at least 1,800MW of battery storage by 2024.

None of this is intended to provide a consistent source of electricity. They're intended to fill in the gaps from uneven renewable energy production or other disruptions. Apparently, it's been working very well in Southern Australia.

Thermal storage is a promising solution because it will likely end up being considerably cheaper than batteries. The most promising type is salt storage for concentrated solar plants. They can potentially store enough heat energy to maintain consistent output all night long. Wind doesn't get that same deal - currently unused Wind power can only be stored as electricity.