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Plugging electric vehicles in at cheapest time could save on power bills, CMU finds

| Friday, Jan. 24, 2014, 12:01 a.m.

Electric vehicles could drive up power prices without the right equipment to ensure they're charging at the cheapest times, according to research from Carnegie Mellon University.

Sophisticated timers could save $50 to $100 per car by delaying when electric cars tap into the grid, researchers in CMU's Engineering and Public Policy Department said. If owners plug their cars in when they get home — as everyone else arrives home to turn on lights, TVs and ovens — it hikes prices by adding demand at a peak time, they said.

“If you charge cars when people get home, you use the ... power plants that are most expensive,” said Allison Weis, a CMU doctoral candidate whose work is funded in part by the National Science Foundation. “We're just trying to capture how much money is on the table.”

The CMU researchers came up with their numbers by crunching data on New York power plants. Government agencies track power plant usage, and the researchers put that data into models that projected how much money would be wasted if electric cars are charged at times of peak demand. All of the work came from data modeling, not from testing cars.

There are about 2 million electric or partially electric vehicles in use nationwide, according to the federal government. There will be 10.1 million on U.S. roads by 2022, according to research released this month by Navigant Consulting Inc. If they're all charging at peak times, it adds costs for everybody.

Some cars come equipped with timers, which save about $50 a year by delaying charging until late at night, when demand is lower and grid operators can run only the cheapest of power plants, Weis said. The savings could grow to $70 to $100 a year if those devices were more sophisticated and communicated with the grid, so they could accept outside signals to start charging at precisely the cheapest times, she said.

The tricky thing is that most people pay a flat rate for electricity no matter when they use it, meaning car owners wouldn't necessarily see the savings from timing their charges. It would be up to the grid operator or electric providers to use rebates or some other kind of incentive to promote their use, in hopes of reducing demand at peak times and improving reliability for everyone, Weis said.

PJM Interconnection, which runs the region's power grid, could be open to that, spokesman Ray Dotter said. It has partnered with universities and automakers in other pilot programs to help electric vehicles and their owners, he said.

“In a nutshell, that kind of idea makes sense,” he said. “One of the goals of the utility business for decades has been filling the valleys to level the peaks” of demand.

Timothy Puko is a Trib Total Media staff writer. Reach him at 412-320-7991.

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