Electric vehicles are gaining a small foothold in the U.S., but according to the feds, it will remain just that – small. Fossil fuels will power the vast majority of vehicles for the next two and a half decades, with electric cars accounting for a scant 1 percent of vehicles sold in the United States in 2040, according to Uncle Sam.

The U.S. Energy Information Administration Annual Energy Outlook report for 2014 predicts that by 2040, nearly eight in 10 cars sold will run on gasoline, down marginally the number sold last year. The number of diesels rolling out of showrooms will double to 4 percent of all vehicles sold, while hybrids will comprise 5 percent of cars. That's up from 3 percent last year.

But the headline figure is this: The EIA predicts that only 1 percent of total vehicle sales in the U.S. will be plug-in hybrids, with another 1 percent being fully electric in 2040.

"The numbers of LDVs [light duty vehicles] powered by fuels other than gasoline, such as diesel, electricity, or E85, or equipped with hybrid drive trains, such as plug-in hybrid or gasoline hybrid electric, increase modestly from 18 percent of new sales in 2012 to 22 percent in 2040," the report states.

Last year, around 14.5 million vehicles were sold nationwide. If the EIA's numbers pan out (and overall vehicle sales stay about the same), fewer than 300,000 EVs and plug-in hybrids will be sold in 2040. That's bad news for the Obama administration, which has long hoped to see 1 million EVs and plug-in hybrids on the road by 2015.

While these estimates are a buzzkill for EV proponents, taking the longview puts things into perspective. The internal combustion engine has been around for over a century, it's dirt cheap and technological advances like direct injection and old tricks like turbocharging keep increasing efficiency. And as much as we like cars with cords, the technology is hampered – at least in the eyes of many consumers – by range and cost concerns. It's difficult to predict the future, of course, but the odds of a major battery tech breakthrough in the next decade remain slim.

The numbers laid out by the EIA jibe with those in last year's report, suggesting the long-term adoption of electric vehicles in all their guises – battery electric and hydrogen fuel cell – will be far slower than advocates would have you believe. The good news is that although we'll still be using lots of gasoline, the average fuel economy of all vehicles sold in the United States will rise from 21.5 mpg last year to 37.2 mpg by 2040 as gas prices will only rise to $3.90 a gallon (adjusted for inflation), compared to the previous forecast of $4.40.