Elon Musk revealed on Thursday the next big date on Tesla’s calendar that’s not related to the Model 3. In fact, it has to do with the eighteen-wheeler lurking in the background for nearly a year, the Tesla Semi.

“Tesla Semi truck unveil set for September,” Musk declared to his 8.18 million followers on Twitter. “Team has done an amazing job. Seriously next level.”

So we know that Tesla’s semi truck will be electric, but the fact that it could be autonomous — driving on a highway is far less challenging than in a city — could dramatically change the economy.

“I think the role of [truck] driver will sort of translate to ‘fleet manager’,” Musk has said. “I think that’s a more interesting job than driving one.”

Musk formally announced Tesla’s intentions to build a semi truck in his “Master Plan, Part Deux,” one of many big changes planned for the company published on the Tesla website in July 2016. In an interview on CNBC in November, he described his vision for “fleet managers” who would control many trucks at a single time. In February of this year, he confirmed the Tesla Semi was still in the works. And today, we know when the world will get an official first look.

The Nikola One

While there’s another clean-tech semi-maker on the market — the hydrogen fuel, cell-powered Nikola One — Tesla’s market power seems likely to make it an immediate leader. In December, Nikola trucking — named after Nikola Tesla — unveiled the hydrogen-powered Nikola One and announced that it wanted to build a $1 billion manufacturing facility in the United States, and said it wants to establish a network of hydrogen fuel stations in 2018.

When Tesla enters the market, it’s likely that the truck will operate on some version of the charging network Tesla has set up — but with a large truck and a large trailer, there’s a lot of space for Tesla solar panels and plenty of room for semi-sized batteries.

Photos via Getty Images / Pascal Le Segretain