Here's a CleanTechnica article from last year that sheds some light on this question, reporting about Fremont production capacity constraints, when the factory was inspected by independent car industry experts:
- "So, what do Galliers and Ellinghorst think about the big question: can Tesla sustain, and hopefully increase, its production rate? “Based off our tour and what we saw, we see no reason why Stamping and General Assembly should not be able to handle [seven to eight thousand cars per week] today, and even potentially 10k units, with very little incremental Capex. We believe the same is also true for the Paint Shop when it comes to reaching 8k units a week, with some incremental capex potentially required to get to 10k units."
- "For Body, our understanding is that incremental capex is required (our impression is in the tens and not hundreds of millions) in order to get to both 8k units and eventually 10k units."
That report was I think forgotten about and maybe even discarded by many investors due to Q1'2019 - but I think the audit by Galliers and Ellinghorst can still be trusted.
I presume their conclusions strongly implies that the press lines already had the capacity back then - and they had more than a year since then, and probably some of the Model Y capacity in shared facilities might already be online:
- stamp lines,
- paint shop expansion (underutilized due to S/X weakness as well),
- seat factory,
- plastics workshop,
- powertrain factory,
- glass factory,
- battery pack factory, etc.
One GF1 leak reported that Tesla planners expressed an "aspirational" goal of GF1 pack production rate of
15k/week - but then settled on "only" 10k/week by the end of next month...
Even with GF3 that's a
lot of battery packs, which must be going somewhere?
Model Y production requires a new body line and a new general assembly line - but much of it is in the expansion of the above shared facilities. (Maybe
@Krugerrand wants to correct any mistakes in my thinking, or add to this line of thought.)
What better way to stress test much of the Model Y production capacity and ramping up the shared part of the supply chain by actually using it for Model 3 production for a "peak quarter" - and then in Q1 and Q2 gradually shift those supplies to GF3 and Model Y production, without having to do an intrusive, time consuming ramp-up of the supply chain, which process is also stock full of operational risks due to the many moving parts largely out of Tesla's control?
(Obviously take this with a big grain of salt, not advice, your options will most likely expire worthless, etc.)