But while the plug-in sales will likely stay low for awhile, both ebbing and flowing, one green model benefited greatly in April: the ur-hybrid Toyota Prius.
Now that all four Prius models are available at dealerships, they're flying out the doors almost as fast as they can be unloaded off the transporters.
Last month, Toyota sold 25,168 Prius models--more than double the 12,477 it sold in April last year.
That's not quite the 28,711 Priuses sold in March--the all-time record for the model range--but it's still more than the highest-ever monthly sales before this year, which were 24,009 in May 2007.
That pushed the Prius ahead of the Corolla compact for the second month in a row. For the year, it's possible the Prius could become Toyota's second-highest selling car line, trailing only the mid-size Camry, which was redesigned for 2012.
While high gas prices have undoubtedly helped sales of the core Prius liftback model, three new Priuses have expanded the model's reach significantly.
2012 Toyota Prius C launch, Detroit Auto Show
The Prius V wagon gives families a larger hybrid with more space for people and their stuff, and still returns a combined 42 mpg EPA rating.
The Prius C subcompact hatchback is a new, smaller car under the Prius name, delivering the same 50 mpg as the mid-size liftback in a smaller, funkier, and less Space Age-y package with a base price under $20,000.
And the Prius Plug-In Hybrid is the company's first production plug-in car, essentially a standard Prius with a battery pack about four times as large that can be recharged by plugging it into a wall socket.
It also, critically, gives the company a car that qualifies for the all-important single-occupant HOV-Lane access in California.
2012 Toyota Prius Plug-In Hybrid - production model
Together, the three new models added 9,507 cars to the 15,661 Prius liftbacks sold last month.
The breakdown is 4,006 Prius C models (or 16 percent of all Prius sales), followed by 3,847 Prius V models (15 percent) and 1,654 plug-ins (7 percent).
Even Toyota says it's not sure where the Prius mix will settle down.
But based on discussions at our Toyota Prius C first drive, we suspect that 65 percent Liftback, 15 percent each for Prius C and Prius V, and about 5 percent for the plug-in would be a mix the company would be comfortable with.
Can Toyota keep up the pace? Or will Prius sales plummet if gas prices slowly wane back toward $3.50 a gallon or less?
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