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 — 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.