President Barack Obama's goal was to have 1 million electric vehicles (EV) and plug-in hybrids (PHEV) on the United States' roads by the end of last year. However, many factors including low gas prices prevented the U.S. president from reaching that figure.

EV sales are still slow. Reuters points out that they dropped about 6 percent last year to around 115,000 units, and less than half a million e-cars are on American roads today, according to CNET.

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Obama set the goal in 2008 around the time of the Great Recession. The price of gas was sky-high at almost $4 per gallon and EV technology was new, according to Automotive News.

Since then the Obama administration has backed billions of dollars in EV financial support for consumers and the auto industry. However, the very low fuel prices of about $2 per gallon in most of the country have increased the sales of big vehicles such as SUVs.

Only around 40,000 e-cars have been sold since 2008. Last year he auto industry offered around 30 plug-in hybrid models that were often greatly discounted, but sales dropped 6 percent from 2013.

In addition to super-low gas prices, EV technology is very expensive. Car makers are just starting to design electric cars that can travel 200 miles on a single charge, including Chevrolet's $30,000 Bolt EV, and Tesla's Model 3 that is rumored to have a similar price tag and range.

Automakers might also roll out some electric trucks. They include Ford's hybrid F-150 that the company announced will hit the market before 2020.

More options and stricter fuel-economy regulations could boost future EV sales.

At the Detroit Auto Show last week automakers showcased several green cars. They included General Motors' new Bolt EV, Ford's plug-in version of Ford Fusion, and Fiat Chrysler Automobiles' Pacifica minivan, which is its first plug-in hybrid.

Obama was scheduled to visit Detroit on January 21, Wednesday. The purpose was to talk about the state of the U.S. auto industry.

Last week during his State of the Union Address Obama did not mention electric vehicles. However, he argued that the auto industry should shift away from high-polluting energy sources.