When you propose a "green credit" instead of a "carbon tax", what do you mean? Is it just a different name for the same thing, or would it work differently? If it would work differently, then HOW? I'm assuming that a carbon tax would put a fixed tax per weight of C02 released charged either to the end-user or somewhere higher in the value chain (eg: a gas tax).
I'd want to put driving-less on similar footing to buying a fancier car.
A carbon tax does that automatically with no extra bureaucracy.
(I'm all for taking the proceeds of a carbon tax and distributing them equally amongst all voters, if you want to make the whole thing revenue neutral for both the government and the 'average' consumer.)