Electric cars are currently getting most of the attention paid to alternative fuel vehicles, and for good reason. The technology behind such vehicles is set to improve at a fast pace in the coming years, and the infrastructure to support them will also be built out quickly. However, another form of alternative energy is already selling more than electric vehicles, and is predicted to do so for at least the remainder of the decade.

Market research firm Navigant Research today released a new report predicting that vehicles that run on natural gas will continue to become more popular in the coming years. The firm estimates that the number of natural gas vehicles (NVGs) sold in 2020 will be 3.3 million – a full 50% increase from the estimated 2.2 million natural gas vehicles that are to be sold this year.

“Several forces are combining to drive sustained growth in the NGV market,” said Dave Hurst, principal research analyst at Navigant. “Vehicle manufacturers are facing increasingly strict fuel economy and emissions requirements that NGVs can help to meet, and many governments are offering purchase incentives to vehicle buyers. The most aggressive incentives, in several states within the United States, as well as in France and Italy, include tax rebates that cover much of the incremental purchase cost for these vehicles.”

Navigant estimates that the lower price of natural gas will inevitably propel the industry forward. Natural gas compressed for use in vehicles is currently estimated to cost 41% less than than gasoline. However, the equipment used in natural gas vehicles requires a higher up-front cost, meaning that it may take years for natural gas vehicles to save drivers money on fuel.