The average kwh cost in the US is about twelve cents, or $0.90 to $1.20 to go 25 miles.
PG&E has standard rate plans that vary from 11c/kWh (which is so little that you can't afford a refrigerator) to 30c/kWh. There are also special plans (time- and season-driven); one of them is specifically intended for charging EVs. In that plan, IIRC, the rate is about 5 c/kWh - but that is at night only. I do not recall what is the rate during the day. Utilities hide the actual rate tables. PG&E has a convenient calculator. I tried it with Tesla S60 and 60 miles per day. I got about $150/mo on plan EV-A.
60 miles per day * 30 = 1800 miles per month. If we convert this to a gas car, $150 pays for about 42 gallons of gas. This results in efficiency of 42.85 mpg. This not something to write home about. My own Prius does 52 mpg on flat land, and 45 mpg if you add climbing of the surrounding hills. If these calculations are correct, it is not efficient to use an EV even if you got it for free. At best it equals the hybrid that costs a third of the price of the EV.
I'm not sure I understand their math. A Tesla 60 gets at least 3 miles per kWh (http://www.teslamotors.com/goelectric#range), so your 60 mile day would take about 20 kWh. At 5 cents per kWh, that is $1/day, so about $30/month. To get a cost of $150/month would take electricity at $.25/kWh. At $.05/kWh, you end up getting more than 200 miles/gallon equivalent, and that's if gas is $3.57/gal. Around here (Bay area) it's closer to $3.80. Like I said, the math is squirrelly.