The Economist has reported on research from the University of Delaware that shows using an electric cars battery for 'vehicle to grid' (V2G) power may make EV owners an income of $4000 a year. That is a sum far greater than the $225 that Nissan, for instance, thinks will be the average annual cost of the electricity needed to power one of its Leafs.
The researchers have been running a fleet of 7 EVs for the past 3 years linked up to the local electricity company's servers by a wireless system that monitors their activity, in order to predict when each car is likely to be available as a power supply.
EV batteries connected to the grid can be used to replace a utility's rapid response peaking facilities, usually a gas turbine generator. The costs saved can be passed on to EV owners in proportion to when and for how long the cars battery is made avaliable for power supply. In Delaware the tariff paid is $0.30 per hour plus a fixed fee payable just for being part of the system.
So not only can EV owners 'fill' their car for as little as $1.00 (compared to the $60-80 a tank of petrol costs), they can also earn income for just having the car plugged in while they're not driving it and make a tidy profit.