Electric cars to save the world?

According to a piece in yesterday's Guardian, Geoff Hoon reckons that electric cars may be one way to deal with the extra emissions generated by a third runway at Heathrow:

They could solve the Heathrow problem: a 5% switch to electric cars would offset the extra emissions. But they are prohibitively expensive because the batteries cost a minor fortune. The sports version comes with a price tag of £100,000, the battery accounts for £60,000 of that. Hoon is looking at ways of subsidising the cost of the battery: "So maybe we buy the batteries and then rent them to people."

Hoon's claim about how a modest increase in the use of electric cars would offset the increased Heathrow emissions shows how he is deploying his skills as a lawyer to master highly technical details.

Although the language is somewhat equivocal, this seems to imply that electric cars might be able to offset the pollution caused by air travel, as if the electricity for the cars wasn't being produced by some coal fired monster a few hundred miles away. And if this isn't what Hoon is trying to say — if he's purely referring to local emissions around the airport — then it can't be counted as a point in favour of a third runway...