The number of hybrids, plug-in hybrids, and electric vehicles on the U.S. market is expected to nearly quadruple by 2020 to 153 offerings from 40 last year. But many consumers don’t want to pay as much as $6,000 extra for a hybrid when they can get 40 mpg on the highway in a standard car with an improved, more efficient conventional engine. Gasoline-powered cars are making headway against hybrids, which saw U.S. share slip to 2.2 percent last year from 2.8 percent in 2009.