[rickycook]

possibly, but what do you consider “write ability”? someone mentioned in another comment that if you control enough high power devices that report status to the grid (eg car chargers) so that the grid can take action (so read only but some other system uses it to take action) you can do plenty of damage

they don’t really have write access, but they kinda do?

[toomuchtodo]

Write access, in my opinion, is where you have enough control to remotely override life critical or physical control systems that could cause death and/or significant physical damage to infrastructure and related failsafe systems can be bypassed or their thresholds exceeded intentionally.

An Internet rando should not have the ability to disconnect your 700kva interconnect over the public internet. If you breach Tesla and can command enough vehicles to charge in a constrained area to overload local distributed infrastructure, failsafes should kick in and physically segregate loads from the local grid.

Disclaimer: This is only my opinion as an infosec practitioner having done some infosec/GRC consulting for investor owed and coop utilities for FERC compliance.