I live in Southern California and had a Tesla wall charger installed. No effect on property taxes I am aware of. I am not a real estate expert, but I am pretty sure your property taxes only increase if you add permitted square footage to the house.
Actually, CA property taxes could increase even without adding square footage, for example if you did a substantial restore to make the house “new”. Another example would be if you changed a garage into a bedroom.
Some improvements such as adding solar energy are exempt from reassessment, but adding EVSE is not. But I’ve never heard of anyone in my area getting reassessed for installing an EVSE.
CA law is that only the portion of the property which was newly constructed is subject to reassessment at market value. Say adding an EVSE adds $1K in property value. The average property tax rate in CA is less than 1% per year, I.e., less than $10 per year. My guess is that it isn’t worth it for the county to reassess.