Before. Although it is possible to do an instant transfer ( I have done it for real estate transactions several times) I made a conventional request for Tesla. Normally Tesla confirms good funds when they accept a check, so from an availability perspective it makes no difference. Just for a slightly pedantic verification:
Fedwire- a domestic US instant transfer system. Often banks charge customers to do those. My own bank does not charge so I have them use Fedwire for my time-critical transfers, including buying my Tesla. Fedwire makes each transaction individually, so is more expensive than,
ACH- a batch-based system to do large volumes of transactions between banks, including payroll, automated recurring payments and non-time-sensitive transfers. Technically ACH is a net settlement system rather than an individual transfer system.
Generically most people call both of these ACH, confusing the issues. I did that earlier, to my chagrin, since I spent decades working within the industry on SWIFT, ACH (actually NACHA) and various Fedwire and FedACH permutations.
FWIW, many retail bankers do not know the difference between these arcane methods which, except for SWIFT are US domestic operations only. US$ offshore transactions are somewhat different.
So, net, for buying a Tesla one needs confirmed funds availability when buying one because even with a check uncleared funds will not work, because banks will not confirm payment availability based on uncleared funds.
The simplest way with Tesla is to use Fedwire if you are needing same day delivery, check or ACH if not. ACH will consistently have next day availability but not always, because not all banks reconcile ACH upon receipt of the ACH files, especially small ones and greedy big ones.
Yes, I know, too much information.