Tesla has started building its next-generation Megapack 3 grid battery, with the first units rolling off the line at the company’s new Megafactory in Brookshire, Texas.

The plant went from groundbreaking to production in 16 months and is designed to build 50 GWh of Megapack 3 a year. That’s the version Tesla says packs roughly 28% more energy into the same footprint as the Megapack it replaces.