Another option is just stick to a smaller circuit.

80% of 15A x 120V = 1.4 kW

80% of 20A x 240V = 3.8 kW

Just going from a standard 15A outlet to a 20A/240V nearly triples the amount of power, and many homes that would need a new panel for a 50A charger have room for one more 20A circuit. Cars typically spend 8-16 hrs per day stationary in their own driveway, so 3.8 kW translates into tons of range.

While 40A or 50A is nice to have, it's far from necessary.

How many amps is your current service? I have 200A service where I live, but the house is 100% electric -- water heater, range, heat pump, washer, dryer, etc. All electric. There's even a little medallion on the front of the house about it: https://i.imgur.com/BrHj1XQ.jpeg The 70s were weird.

And when you say that your panel is old, just how old are we talking?