Based on the following sentences from the article, it's probably 4 to 6 times more than 15.7 GWh (60 to 90 GWh, apparently):
"Battery energy storage is not without challenges, however. Lithium-ion batteries — the most common type used for energy storage — typically have about four to six hours of capacity. It’s enough to support the grid during peak hours as the sun sets, but can still leave some gaps to be filled by natural gas."
"Battery energy storage is not without challenges, however. Lithium-ion batteries — the most common type used for energy storage — typically have about four to six hours of capacity. It’s enough to support the grid during peak hours as the sun sets, but can still leave some gaps to be filled by natural gas."