SPECIAL EDITION CARS & CAR CARE (Honda's gasoline-electric car, the Insight, goes on sale late in 1999  -- the first hybrid vehi

When it comes to predicting plug-in vehicle sales during their early years of market availability and how they compare with the early hybrids a decade ago, the forecast calls for...fog. Analysts pointing to higher-at-this-stage-of-the-game sales for plug-ins may be overly optimistic about plug-in sales because of different market conditions and product availability, Plug In Cars says.

The good news is that Americans may buy about 90,000 plug-ins this year, compared to about 35,000 hybrids bought in 2002 (2002 and 2013 represent Year Four of widespread availability for hybrids and plug-ins, respectively). That said, the only two hybrids available in 2002 were the first-generation Toyota Prius and the original two-seater Honda Insight, and neither of those models generated either the level of public buzz or marketing dollars that the Nissan Leaf, Tesla Model S and Chevrolet Volt have. Hybrid sales, which now account for about four percent of total vehicle sales, didn't gain momentum until the release of the 2004 Prius, a time when gas prices started spiking.

Regardless, plug-in proponents can revel in the fact that US plug-in sales through September were up 90 percent from a year earlier, and more plug-in models are on the way.