Yes gas at the moment is cheap, conventional car sales are up, regular hybrid sales are down, but … in the U.S. last year, sales of plug-in electrified vehicles (PEVs) including all-electric and plug-in hybrids rose by 23 percent.

To date, Americans have purchased close to a third of one-million PEVs, globally around three-quarters of one million have been sold, and the first million worldwide is projected by this year.

Although PEVs now comprise just three-quarters of one percent of the 16.4 million passenger vehicle market in the U.S. – which is the world’s largest PEV adopter – the growth is happening against resistance and appears to be accelerating.

Why are these vehicles being introduced, and why are people buying them? There are a variety of views on this floating out there, some informed, some not as much.

Following are seven major interrelated factors driving the development and purchase of plug-in vehicles, and no doubt, some of you could come up with more.