A Million Electric Cars: A Big Load, but Manageable

Jim Motavalli

Jim Motavalli | Feb 23, 2011

President Obama has thrown down a gauntlet--he wants to see a million plug-in cars on the road by 2015. That, as Bill Cosby once said about his memorably large neighbor Albert, is a big load. Is the entire electric infrastructure of the United States, commonly known as the grid, going to blow to smithereens if all these new battery vehicles plug in at once?


Charging the Nissan Leaf: Add 999,999 more and it's an issue. (Flickr/Department for Communities and Local Government photo)
Charging the Nissan Leaf: Add 999,999 more and it's an issue. (Flickr/Department for Communities and Local Government photo)

For one thing, they're not going to plug in at once. I queried the Electric Power Research Institute on this, and they came back with an analogy - do you know the tall tale about the New York City sewer system flooding during the first Super Bowl commercial? The reason that never actually happened is because of a phenomenon known as "load diversity." Everyone didn't flush at once, and people won't plug in at once.

But it's still interesting to figure out the size of the load if everybody did flip the switch simultaneously. The Nissan Leaf is a 3.3-kilowatt load, so it's simple enough to multiply that by a million and get 3.3 gigawatts, which sounds scary but is actually only 0.3 percent of the world's installed electric capacity.

There's a surprisingly small amount of research on this question. The 2010 "Assessment of Plug-in Electric Vehicle Integration" by a coalition of U.S. and Canadian companies, predicts that the load might be 3.7 gigawatts, or the output of three or four large power plants.

We can handle this, especially since it's all but certain the cars will be charged not during peak times but at night, when utilities lower their rates and the grid is loaded with excess capacity. In fact, there's a beautiful synergy with renewables, because wind power is strongest at night and right now many turbines are pumping energy into the grid that the system can't use.

If we spread our three-gigawatt load over an eight-hour period, the load at any one time would be reduced to 819 megawatts. Stagger it over 12 hours, and only 546 new megawatts need to be found. As the eco-journalism web site Treehugger points out, "That's nothing!" Well, it's not nothing, but it isn't something that will be frying the world's transformers left and right. Utilities say they aren't worried.

Fast charging the Mitsubishi at 480 volts. (Jim Motavalli photo)
Fast charging the Mitsubishi at 480 volts. (Jim Motavalli photo)

The bigger threat, actually, is clustering. Nissan says that a huge number of its early Leaf battery electric customers are moving over from a Toyota Prius (it's the next step up, isn't it?). And Priuses cluster in certain states (California, Washington, Oregon, New York) and, even more in certain zip codes. Those neighborhoods are at risk of transformer burnout, especially since we lack a smart grid.

Believe it or not, those smart-looking guys in the utility control rooms really have no idea of the load beyond the local transformer level -- they don't know if you or your neighbor is plugging in a car until they send out a meter reader. That's 1940s technology at work.

Utilities, including PG...E, are preparing for this (or at least trying to) by getting its customers to write in and identify themselves as likely EV buyers. And they're studying the GPS coordinates of Prius owners, all in an effort to identify cluster locales and beef up the system at those choke points. It has aspects of a military campaign, doesn't it?

Meanwhile, smart meter distribution proceeds, but not quickly enough. It doesn't help that some fringe folks are convinced that smart meters are zapping them with electromagnetic rays.

Electric cars do have challenges. They'll be expensive to buy, at least initially, and range anxiety is a real thing, especially in the cold weather. But don't worry about the load to the grid--we'll be able to handle that one.

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