What happened 

Shares of natural gas fuel specialist Clean Energy Fuels Corp (CLNE 2.52%) fell 29% in 2017, according to data provided by S&P Global Market Intelligence, as the company's financial results began to deteriorate. It has struggled to gain traction in the past few years, but last year it became apparent that widespread adoption of natural gas-powered vehicles may not ever happen. 

So what 

There's a chart showing the three-year slide in results below, but we don't have to look back much further than the third-quarter earnings report to see how poorly Clean Energy Fuels is doing. After reporting a $94.1 million loss for the period, including a $73.8 million charge relating to closing 42 stations, there doesn't appear to be much momentum in operations. These closures are all "underperforming" according to management, but the fact that many stations can miss expectations is pretty astounding for a business that should still be in growth mode. 

Car being filled with natural gas.

Image source: Getty Images.

It's hard to see how Clean Energy Fuels will be able to generate enough money to make a profit unless alternative fuel tax credits continue to provide regular benefits. There's just not enough interest in converting vehicle fleets to natural gas, making the entire business model an uphill battle. 

CLNE Revenue (TTM) Chart

CLNE Revenue (TTM) data by YCharts.

Now what

A few years ago, the thought was that Clean Energy Fuels would benefit from commercial vehicle fleets converting to natural gas because it was cheaper and cleaner than diesel. But that thesis has been undermined by battery-powered vehicles becoming even more cost-effective for commercial users. Buses, large trucks, and even semis are already being produced or pre-sold to commercial operators, and once they go electric, it's unlikely they'll ever come back to natural gas as a fueling option.