 The vehicle seller Carvana is letting customers take advantage of federal tax incentives early for certain hybrid and electric vehicles, allowing buyers to trim up to $4,000 off the price of a used plug-in hybrid or EV. Carvana says it's a quicker way to take advantage of the federal tax credit for buying a used electric vehicle or hybrid before next year's tax refunds. That announcement comes as sales of EVs in the U.S. have slowed this year.