Marco “Speedy” Jeanrenaud, a resident of the Lake Geneva region of Switzerland, is a connoisseur of the automobile. A lover of classic American cars, he has owned a 1976 Cadillac, a Dodge Charger, several Ford Mustangs, a Range Rover SUV, and Harley and BMW motorcycles (as well as more prosaic vehicles, including a Hyundai minivan and a Honda Civic).

He was always highly skeptical of hybrids and EVs, but like most of his performance-loving ilk, was intrigued by Tesla. He took a couple of test drives, but wasn’t ready to step on the pedal until one day when he went to a launch event for a new Jaguar. There was a Model S next to the new Jag in the parking lot, and that was all anyone at the party seemed to be talking about.

After another test drive and a few long talks with his wife, Mr. Jeanrenaud bought a dealer demonstrator Model S 70D for a bargain price of 74,000 Swiss francs ($75,480).

A couple of months later, Speedy is an ordained Tesla EVangelist, explaining to anyone who will listen why they ought to go electric too. He plans to have solar panels installed on his house by the Swiss branch of SolarCity.

The performance and amenities of the Model S are far superior to any car Mr. Jeanrenaud has driven, and he’s convinced that, in the long run, the Tesla is cheaper as well. To prove it, the analytically-minded Swiss prepared a spreadsheet with data on his favorite cars that he’s owned. He assumed usage of 40,000 km/year, and a gas price of 1.50 francs per liter. Based on data provided by his local electric utility, he assumed an electricity cost of 3 francs per 100 km.