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?