It has been 7 months already and we've put over 5,850 miles on our electric car. During that time we've charged 196 times at 11 different charging stations, and never once paid for gas or waited for the tank to fill. One of the great things about electric vehicle charging stations, particularly those from ChargePoint is how they are networked and provide an online dashboard where you can view personal charging history and energy consumption. Our home charging station has a built in cellular uplink and is connected to an online account so all charges from home are automatically visible on the website. At public charging stations I scan an RFID card on my keyring to associate the charge with my account.
Using this website, I see that of those 5,850 miles, I used over 2,114 kWh of electricity. 27% of that electricity was consumed overnight by our home charging station in our garage, and the other 73% was provided free by the charging stations at my employer or the free charging stations at San Francisco city parking garages.
In our first month of owning the car, we didn't even have a home charger, and so we were charging exclusively for free, but not really putting that many miles on the car each day. Now that my wife is commuting further to work each day, we put over 50 miles a day and charge it up at home each night and at a parking garage in San Francisco each day while she is at work.
If we assume an electricity price of $0.12 per kWh, then it cost 2,114 * 27% * $0.12 = $68.49 in electricity to drive those 5,850 miles. Gas is approximately $5/gallon in Silicon Valley right now, so $68.49 would buy less than 14 gallons of gas (1 tank!). I'd have to get 418 miles per gallon to come out ahead with a gas car given how much of my driving is subsidized by free electric vehicle charging stations.