The cost of electric and gas is virtually the same. If you look at PG&E in Northern California, the tier 2 rate is .17 cents per kwh, using the formula of 16 amps x 240 volts = 3,840/1000 = 3.84 kwh x 4.5 hours = giving you 17.28 total kwh x .17 cent rate = of $2.93 for 50 miles. That works out to .0588 cents per mile. At gas here at 2.59 per gallon at 42 miles a gallon, the cost is .0617. So there's little benefit now.