The generation and demand in a power grid with an increasing share of renewables will hardly be reconcilable without large storage and reserve capacities. The possibility to use the fleet of electric vehicles both as a power sink in times of overproduction, as well as to take at times of low production energy from the vehicles back to the grid stabilization, has already been addressed. However, the question is: what should motivate car owners to wear their batteries to the community, even if this wear is very low? In order to regulate supply and demand, one usually uses the price in a market economy. Amazingly, the consumer always pays the electricity supplier the same, regardless of whether he is drawing electricity when it is scarce, or when there are massive surpluses. These fluctuations in supply and demand can be clearly seen in the spot prices of the power exchange, which provide daily information about the available amount of electricity and thus the associated price for every hour of the day. With a relatively simple trick, you could implement nationwide energy management: put a signal on the power line that tells the device at the end of the line (such as a washing machine or electric car charger) the current electricity price. If you then as a consumer of your washing machine specify a maximum price of electricity such as 10 cents per kWh, the washing machine "waits" with the start until the power overproduction has reached a level that drops the price to less than 10 cents. Naturally, with increasing over-production of electricity, the price of electricity will become lower and more and more devices will be switched on in this way, until, similar to the stock exchange, a certain price level has settled. Cars with a large battery will therefore be charged from an economic point of view during times of overproduction. However, if the electricity demand is greater than the power production, the car owners will "allow" their vehicles from a certain price per kWh, again to give a portion of the energy of their battery into the grid. They do so for purely economic reasons. A modern battery in an electric vehicle can be charged more than 2000 times in about 8-10 years. With a range of about 500 km of these cars, this results in a possible mileage of 500 km times 2000, so theoretically about one million km. Half of them, half a million km, have already covered a Tesla Model X in the US and the battery still has more than 90% of its initial capacity. Since hardly a car owner will cover such long distances within the lifetime of his vehicle battery, he can thus behave grid-friendly without having the risk of heavy wear of his battery, and he can at the same time earn something by the electricity sales in times of low power generation in the wind and solar power plants. Of course, this is not possible when you are on your way to vacation. If you are at work during the day and the vehicle is parked at the company car park, or at night in the garage, or in the parking lot connected to a bidirectional charger, that would be easily possible because an average car is idle for more than 90% of its time.
 Lithium ion batteries wear very little in a SOC range between 50-75%, and this is the range that would be favored for grid stabilization