"Electricity isn't a "heck of a lot cheaper". It isn't cheaper at all."
The article said it cost a quarter to plug in the car. That's a lot less than it would cost to go to the gas station.
A day maybe, otherwise it is simply a lie.
A quarter will buy you about 2kW/h of electricity in California - at best.
That amount of energy is enough to charge two standard car batteries (75 Amp/hours each) without losses.
2kW/h of electricity is about 2.68 horsepower for an hour. Again without losses.
So if he drives 15 minutes a day he'd be picking up about 10.7 horsepower from the batteries total over the duration of the trip without losses. There are losses.
If he travels 10 miles a day (he lives in San Francisco so that is easily possible) and his Prius gets 45 mpg normally he’ll use about 0.222 gallons of gas a day (or $0.62 @ $2.80 a gallon) without adding his batteries. If he now gets “80 mpg” then he’ll use about 0.125 gallons of gas a day instead (or $0.35 @ $2.80 a gallon). That translates into a net gas cost savings of about $0.27 a day. So electricity costs of “a quarter” a day would be close.
I doubt he knows exactly how much power he’s using to charge his batteries every night. Nothing else in the article is specific.