Consider an average weekday afternoon in the electric car-dominated future of some typical California suburb: many thousands of plug-in cars returning from typically brutal commutes with batteries sliding toward empty. Some of them will plug in at home, using higher voltage clothes dryer outlets or even 120 V regular wall sockets (for those that don’t mind waiting actual days for a charge), while others will stop off at public charging stations with “level 3” charging ability, e.g. the ability to juice your Leaf up to 80 percent in less than an hour. Whatever the exact charging source, the basic result is a whole lot of high voltage outlets delivering at maximum capacity in a short amount of time.
If you really wanted to piss off an electric grid that's just what you'd do, plug in a bunch of current-sucking devices at once. Look at heatwave brownouts, for example, as highly concentrated groups of people all crank their air conditioners in unison and keep them cranked. This results in equipment failures within overtaxed infrastructure—tons of bonus current overheating and blowing up transformers, for starters—and as a result, you find power companies dropping the voltage available to the grid to protect the stuff that makes said grid work. That's a brownout.
The grid is more or less premised on the notion that your home can survive well enough on 120 V, and almost all of your outlets deliver this voltage. The house itself receives around 220 V and it’s common for homes to have one single special outlet that delivers all of those volts. This is typically with a clothes dryer in mind, but it’ll get more and more common for electric car owners to add another one of these higher voltage outlets somewhere for their vehicles. So, imagine entire cities all running their clothes dryers at once. It’d put a New York heatwave to shame. The electric car future is a looming problem that makes utility companies anxious, and will demand a solution more clever than upgrading entire physical grid infrastructures.
For the rest of the story: http://motherboard.vice.com/blog/to-keep-electric-cars-powered-the-grid-needs-to-get-even-smarter?trk_source=features10