I have comprehensive insurance on my own car and wonder can I drive my husband's car on 3rd party cover or do I have to be a named driver on his car. Both cars are with the same insurance company.
BTW it's my understanding that driving other cars cover is sufficient for occasional/infrequent use of the "other" car. But if the intention is to drive it more frequently then being a named driver on the other car's policy may be more appropriate. Again you'll need to check the relevant policy schedule and terms and conditions and, if it's still not clear, ask the broker or underwriter for clarification.
Edit: e.g. my AIG policy booklet says that driving other cars is for "in the event of an emergency" so, presumably, not for regular use. Note also the condition about the engine size. (Not sure how that translates for an EV?).
Some insurers have clauses treating "family" differently,
So read any documentation you have and if necessary contact your insurer and note exactly who you are talking to, what they say and the time/date of the conversation.
Or as noted above ask for you to be added to each others policies.