Adding battery due to EV adoption?

I live in the Bay Area, California and last year installed solar so am in NEM 2.0.

My system is:

16 REC panels 6.4 kW with enphase IQ8+ microinverters.

Our current true up for December is $17. We have an Electric stove, washer/dryer, and blast the AC in summer. Have not really had any power outages and the few times we have, it was brief.

Our plan is to finally commit to an EV. The dream is a Rivian R1S suv.

Would it make sense to add a battery/batteries? If so, how much capacity should I be really looking at?

I’m not particularly knowledgeable with solar and EVs so my limited research today appears the batteries I should look towards are either the Enphase 5P or a Tesla Powerwall (though I also read that Tesla will eventually release a Powerwall 3 that should be a nice upgrade from their current 2).

Also, can we claim the tax rebate on just batteries (since we already claimed for the solar this tax season)?