Americans may be driving less, but there are still more than 230 million cars cruising around the U.S. And sometimes those cars break down or get old and their owners want to buy a new one. Getting a greener car saves money on gas, and minimizes your contribution to global warming, but how do you know which green car is best? A new site called RideNerd makes figuring out which car to buy much, much easier.

Basically, you can just plug in two cars that you might be deciding between, and RideNerd will tell you which rates better on their scale — which takes into account metrics like affordability, fuel economy, and climate friendliness.

Just for example, here’s how the Prius c, the cheapest Prius on the site, compares to the Honda Civic.

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And then if you want to scroll down, there’s all sorts of clearly laid out information about details like total annual costs, methane per mile, reviews from other websites, and technical specs. The picture gets a little muddier as the details pile up: The Civic gets slightly higher ratings from other reviewers, and is a little bit bigger. But the Prius c is cheaper, both up front and over time, and does consistently better on all the green criteria. You can guess which one we’d choose.

We chose a relatively budget-friendly comparison to make. But you can get fancy on this site, too. And if the “popular comparisons” column is to be believed, there are plenty of RideNerds out there who are dreaming of buying a Tesla and trying to figure out if they can’t just justify buying a BMW or Audi instead.