The factory currently has an output of about 35 GWh annually using 13 production lines. With the 14th line, the output is expected to increase by roughly 10% to 39 GWh annually. From the previous reports we know that Panasonic potentially could go up to 54 GWh annually.
"Panasonic will boost production capacity of batteries for Tesla next year in an investment expected to exceed $100 million, Nikkei learned on Wednesday.
The investment will be made in Gigafactory 1, a battery plant in the U.S. state of Nevada with 13 production lines. Panasonic will add another line, increasing capacity by 10% to 39 gigawatt-hours per year."
We guess that as both Tesla (as a whole), and Panasonic's battery production in Nevada in particular, are profitable, it's the natural move to increase production and sales. It would be the first expansion since 2017.
""This is not the time to worry about making major investments," a Panasonic official said."
Separately, Panasonic is upgrading its battery chemistry to boost the energy density by 5% later this year, and 20% over five years.
A cool thing about improved energy density is that a 5% gain at 39 GWh annually (assuming that all lines would be upgraded), is equivalent to producing roughly 2 GWh more per year.
Panasonic probably will remain the major Tesla battery supplier, possibly exclusively in North America, as in China Tesla is working with LG Chem, and on a smaller scale with CATL.
We don't have any information whether the increased output will be for increased sales of Model 3/Model Y or is envisioned for the upcoming Tesla Cybertruck/Tesla Semi.