Depends on a few things including the car, how empty your battery is and the cost of electricity.
The Chevy Volt gets 2.7 miles per kilowatt hour. Let's assume you drive 1000 miles per month; you would need to pay for 370 kilowatt hours of electricity. If you pay 12 cents per kilowatt hour (your rate may be higher or lower) that brings your total electric bill to $44.44 for the month.
Thank you that is what I have been wondering about.