We have a Volvo XC90. Much bigger (and probably heavier) than your Bolt. It gets ~26MPG on the gas only mode. It has an 18.8kWh battery and can go ~30 miles on a charge. So again, bigger, heavier, and less efficient. At $0.50 per kWh, it takes ~$9 for 30 miles, and ~$5.5 in gas to go 26 miles.