Considering where you are and the time of year, I would guess you're running A/C in the house during the day. That will probably offset a lot of the charging savings.
Also, are you charging only during the lowest rate? When I looked at what PG&E considers prime charging time, it was a shorter window than I would have expected. In any event, you probably have to charge for more than a couple of hours every night to realize significant savings, especially while everyone is still working/learning remotely and using electricity during the day. I know I wouldn't be driving enough right now to make that happen.