You glide silently out of the Tesla showroom in your sleek new electric Model 3, satisfied you¡¯re looking great and doing your bit for the planet.

But keep going ¡ª you¡¯ll have to drive another 21,725 kilometers before you¡¯re doing less harm to the environment than a gas-guzzling saloon.

That¡¯s the result of a Reuters analysis of data from a model that calculates the lifetime emissions of vehicles, a hotly debated issue that¡¯s taking center stage as governments around the world push for greener transport to meet climate targets.