Why do the panels need to get cheaper to do that? Kettleman SC for instance. Will GF1 employees get free charging?
OK, in general the principle is that the more PV-electricity you produce, the smaller the fraction of that increased production you are able to consume yourself. That in turn means that the incremental cost of increased nameplate capacity goes up, because you will at times have a (peak) PV-production that you cannot utilize (e.g. during summer), for the benefit of having more power available during non-peak production times (e.g. during winter).
So the panels would need to get cheaper, if the GF1 roof-top installation is (or will be) anywhere close to covering their own consumption.
GF1 however has a _lot_ of battery capacity (e.g. from being able to do burn in tests with their production), which changes things.
If we assume for a moment that GF1 has unlimited battery capacity, then they can use all their PV-production as long as it does not actually exceed their electricity consumption, on up to an annual basis.
I think their battery capacity is somewhere below that (ie. that there would be prohibitive costs incurred by keeping battery packs at the factory to store electricity between seasons).
So if at some point (during the summer months) their PV-production starts to exceed their battery capacity for enough weeks, that they cannot store all the electricity and if during the winter months they cannot cover their entire electricity consumption with PV + batteries, then they can opt to increase their nameplate capacity.
This will allow them to be self-supplying to a larger extent also during the winter, but during the summer they will have excess production that they will have to let go to waste. This in turn means that the panels will need to be cheaper for the PV-extension to be profitable, because the added capacity produces at a lower utilization.
Whether this reasoning makes sense depends on the monthly (winter and summer) roof-top production relative to the monthly electricity consumption at GF1, and on the battery capacity available for storing excess production, even between seasons.
As far as I can understand.
PS edit. Net metering is equivalent to unlimited battery capacity, but I believe GF1 does not have that.