Cars running on gasoline have been with us for almost 140 years, and diesels for almost 80 years. More than 1 billion vehicles on the planet use those fuels today.
So the view that liquid hydrocarbon fuels are on their way out requires taking a rather long view.
Now we have one estimate of a timeframe for such a transition, courtesy of the U.S. Energy Information Agency. And it can be summed up as: a very long time.
In an "early release overview" of its Annual Energy Outlook report, released Monday, the agency predicted a sharp rise in average fuel efficiency, resulting from stringent new corporate average fuel economy (CAFE) rules.
And it predicted that total vehicle miles traveled would rise at 0.9 percent per year, from 2,662 billion miles in 2012 to 3,434 billion miles by 2040.
2012 Toyota Prius Plug-In Hybrid - production model
The agency also issued its predictions for the mix of propulsion technologies on U.S. roads in 2040.
It expects diesels to double their share of passenger-vehicle sales, from 2 percent to 4 percent.
Surprisingly, it says just 5 percent of vehicles sold will be full hybrids in 2040.
As for battery-electric vehicles and plug-in hybrids, the agency predicts that each will account for just 1 percent of total vehicle sales that year.
If there are roughly 250 million vehicles in the U.S.--a number that has stayed stable for several years now--that would mean only 2.5 million all-electric cars and another 2.5 million plug-in hybrids will be sold each year fully 25 years from now.
Given improvements in battery costs that average about 7 percent a year, the EIA's predictions are considerably lower than estimates by most auto-industry and energy analysts.