Geothermal company Fervo Energy announced Thursday morning that it had started selling electricity from its Cape Station power plant to the grid on September 30, one day ahead of schedule.

With it, Fervo becomes the first enhanced geothermal company to reach a key commercial milestone. The power plant synchronized with the grid about a week ago, bringing online the first third of what will soon become a 100-megawatt power plant.

The entire site could be much larger, though, with the potential to generate as much as 4 gigawatts of electricity, Fervo previously told TechCrunch.

“No team has ever built a project like this anywhere in the world, and we did it ahead of schedule,” Fervo co-founder and CEO Tim Latimer said in a statement.

From groundbreaking to commercial operations, the first block at Cape Station took 23 months to complete. As Fervo refines its process, it is aiming to complete future blocks in as little as 18 months.