I've installed a natural-gas powered automatic standby generator (20 kW). It's sized large enough to run everything in the house _except_ the Tesla. But as long as I'm not running both air conditioners AND the steam shower, there should be plenty of power left over for the Tesla. If that ever proves not to be the case then the Tesla gets automatically cut off from the generator for a few minutes. No big deal. The additional peace of mind as a hurricane or blizzard bears down on us is palpable. I highly recommend it. Rough costs: $4k for the generator, $4k for the install (but my generator is about as far as possible from the gas source and pretty far from the main panel. YMMV).
Operating off the National Grid or some other natgas supplier?
Thanks,
Alan