In global terms, plug-in car sales are still a drop in the ocean.

That's to be expected--we've only had volume production models for the last three or four years. Disruptive products always take a little while to get going.

But global plug-in electric car sales have now topped 400,000 units--a figure expected to rise into the millions by 2016, if expected increases continue.

What the number alone doesn't tell you--but German research group ZSW notes (via Autoblog Green)--is that 400,000 units is around double the number we had a year ago.

That, in turn, was double the number of electric vehicles we had at the end of 2011 and start of 2012. No other market segment can boast such figures.

Though the figures include plug-in hybrid vehicles as well as pure battery electric cars, the numbers don't include regular hybrids, plug-in motorcycles or large vehicles like buses and trucks.

In terms of countries, the U.S. can hold its head up high, buying more plug-ins than any other country: 174,000 of them by the end of 2013. Japan (68,000) and China (45,000) are next up, with individual European countries following behind. The Netherlands alone touted 30,000 plug-ins by the end of 2013.

Topping the table of individual manufacturers is Nissan, which boasted Leaf sales of 90,000 units by the end of 2013. That number has since crossed 100,000 cars, and as April begins the total will be higher still.

MORE: Plug-In Electric Car Sales In March: Nissan Leaf Has Best March Ever

General Motors is next up, carried by the Volt and to a lesser extent, its European Ampera cousin.

Toyota (fielding its Plug-In Prius), Tesla, PSA (Peugeot-Citroen), Ford and Renault follow, with Daimler, BMW and VW just scraping onto the list.

It's worth noting that the latter German duo are likely to see a spike in plug-in sales over the next few years--BMW will have its i3 and i8 models on the market, while Volkswagen and Audi launch the Volkswagen e-Golf, Golf GTE, e-Up electric city car and Audi's A3 Sportback e-tron.

While plug-in car sales are unlikely to double each year from now on, the numbers will certainly increase, likely hitting a million vehicles by the start of 2016.

That'll still be a drop in the ocean--there were already an estimated billion cars on the world's roads by 2011.

But a million plug-ins is better than no plug-ins at all--and combined fuel and emissions savings will be almost unimaginable.


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