1 to 2 million electric cars have been sold and are circulating. Maybe 20 millions ecars will be sold by 2020.
An ecar has a battery with a storage capacity of 24 to 30 kWh.
Cars are parked 95 % of the day.
20 millions ecars can store 20,000,000 x 30 kWh = 600 Gwh
This is about 60 % of the average daily consumption in France, a country of 67 million people.
These batteries can be used to store excess production of wind energy when the wind is strong.