Old-school Toyota Prius

Despite a challenge by upstarts with cords, the Toyota Prius remains the unofficial car of green-ness. What's sometimes difficult to remember is that the car has been on the market for over a decade, so it's nowhere near an overnight success. We're not sure if we'll ever see the day when half of Santa Monica is driving around in Nissan Leaf electric vehicles, but at least one publication sees history repeating itself – this time with plug-ins in the Prius role.

A new article in Scientific American downplays worries that sales of plug-ins such as the Leaf and Chevrolet Volt have been disappointing. In fact, the publication says electric vehicles and plug-in hybrids are "on track or doing better" than hybrid sales were at the same stage of market introduction.

"We are seeing impressive year-on-year sales, declining battery costs, a decarbonizing power sector, and cities around the world committed to reducing congestion and local air pollution," writes Tali Trigg in Scientific American. Supporting the claim are the cold, hard numbers: about two years after their US introduction, both the Leaf and Volt are selling at almost twice the pace as the Prius did two years after it debuted in the States. And such plug-in numbers, which more than doubled to about 120,000 units worldwide last year, may surge further as volume production rises and battery costs fall.