In the coming years, more and more Ontarians will start plugging in their cars as well as filling them up. And with good reason. The plug-in hybrid electric vehicles (PHEVs) just starting to hit the market can run more than 30 km on their battery charge before switching over to gasoline. That saves consumers money, cuts air pollution, and reduces greenhouse gas emissions.

But what impact will this have on Ontario's electricity grid? Several WISE researchers set out to answer that question.…