The fuel savings are not that big.
But, it really depends on your driving style.
Do you have mountains to go up and down?
Is it all under 35 mph?
Is it stop and go traffic?
Is you daily commute less than half of the cars rated range?
If you drive at low speeds, around town then an electric car will get those kinds of "fuel efficiencies".
But, if not, then it can actually cost more then petrol.
With your solar panels, are you selling electricity back to the grid every month? If not, then you will either have to install more panels or pay the electricity for your vehicle.
And, if you car is parked at work during the day, well, you can't use the sun to charge your car. If you... do the power wall thing, charging a battery to charge another battery, you efficiency falls through the floor.
I used this tool to compare the fuel costs of a possible electric model to the last petrol model I used.
The land here is mostly flat-ish and I would mostly be doing journeys of less than 10miles.
The solar panels get a payout for feeding into the grid, but the way the payments are designed means that we get paid regardless of what we use - so if it's done correctly it should be possible to basically get free charges for the car.