Vehicle-to-grid technology is already being piloted in the UK and will be available to consumers in Q2/Q3 2018. There is an industry-wide roadmap for the development of local electricity markets with real-time pricing. Any customer can choose to have a smart meter installed free of charge; the goal is to have full deployment of smart metering by 2020. These meters use Zigbee to provide real-time consumption data to a wireless display unit. With future firmware upgrades, they will be capable of providing real-time pricing information to smart appliances.

The grid is already perfectly capable of consumer feed-in, hence the huge deployment of photovoltaic solar systems. The metering is not particularly difficult. There is an emerging standard for smart grid communications (LTE on the 450MHz band) that is already in widespread use across the EU.

Completing this transition won't be cheap, but there are no significant roadblocks. We know what needs to be done and we have the technology to do it.

https://www.drive-electric.co.uk/driveelectric-launches-vehi...

http://www.energynetworks.org/assets/files/electricity/futur...

http://450alliance.org/wp-content/uploads/2014/05/WhitePaper...

> Also think about when peak demand happens -- late afternoon on hot summer days. Right at the time when people are getting home, with their EVs discharged (or at least, not at full capacity) after a day's use.

Not completely discharged - the little available per car will add up to a lot when there are a lot of EVs. The EV owners who decide to sell to the grid at peak hours (at higher prices) might make a profit doing so.