With PRIME using EPA rated ~50 mpg and ~25 miles EV range. The rule of the thumb is electric rate ($/kWH) x 6.5 kWh for full EV range. If this is more than half of current gas price, then gas is cheaper. For me. $0.2/kWh x 6.5 kwh = $1.30 for 25 miles. Thus, if gas price/gal is twice as much, or >$2.60, EV becomes more economical. Our gas price just got above this break-even-point last week! WOO WOO!