Charley, Tesla's new battery storage unit won't be storing energy from solar panels nor wind turbines, but from Moss Landing Power Plant - a 1.2 GW combined-cycle gas turbine plant on the same premises. But wait, there's more:

"...CO2 emissions resulting from storage operation are nontrivial when compared to the emissions from electricity generation, ranging from 104 to 407 kg/MWh of delivered energy depending on location, storage operation mode, and assumptions regarding carbon intensity."

Bulk Energy Storage Increases US Electricity System Emissions

Thus, storing Moss Landing's gas-fired electricity will emit 73% more CO2 than generating electricity straight to the grid.

I guess we're supposed to be happy every home in San Francisco can be powered for six hours by the equivalent of a dirty coal plant.

Given the purpose of the battery is to allow owner Vistra to store energy at night then sell it during the day when prices are higher, the only thing "green" about it are the stacks of ratepayer cash Vistra will be hauling to the bank.

PG&E predicts that the Tesla Megapack system will save consumers more than $100 million over the project’s 20-year life span when compared to the forecasted local capacity requirements and procurement costs necessary in absence of the facility

This will be the data to track to see how eager other utilities are to jump into such an arrangement. Curious to see where it all goes!