There are two comparisons: energy equivalence and economic equivalence. One gallon of gas holds 33.7 kwh of energy. My Tesla has averaged 3.85 miles per kwh for its life so 3.85 miles/kwh x 33.7 kwh/gal = 129.7 miles/gal equivalent. If I pay .10/kwh x 33.7 kwh/gal = $3.37 /gal, so for $3.37 I...