I don’t have solar panels but own a house with parking spot.

I use the PG&E EV2-A night tariff at home which is still 0.23 $/kWh, though the rate at work is only 0.14 $/kWh which I use as much as possible. I rarely use the superchargers (0.45$/kWh.) Let’s use the 0.23 value.

I drive 15k miles per year. At roughly 2.5 mi/kWh. That gives $1380 per year.

At 20 mi/gallon and $6/gallon, I’d pay $4500 per year. At today’s gas prices, the difference is IMO not marginal anymore. (That said, I didn’t buy the EV for the drive savings…)