What happened

Clean Energy Fuels (NASDAQ:CLNE) stock cleaned up yesterday, gaining nearly 29% by close of trading. Today, Clean Energy is giving some of those profits back. After plunging as much as 11% in Thursday's early trading, the stock is down 6.5% just before market close.

So what

There was good reason for Clean Energy stock to go up yesterday.

Fourth-quarter sales grew 8% year over year, and Clean Energy booked a solid profit of $0.03 per share, reversing its year-ago loss. The results exceeded analyst expectations, and investors were understandably pleased.

So why is Clean Energy stock declining today? In the absence of any analysts downgrading the stock, or Clean Energy saying anything to shoot itself in the foot today, my best guess is that we're just seeing profit-taking, plain and simple.

Check out the latest earnings call transcript for Clean Energy Fuels.

Green arrow pointing up and red arrow pointing down

Image source: Getty Images.

Now what

After all, Clean Energy is still expected to lose money this year, and analysts are forecasting another full-year loss in 2020. According to analysts polled by S&P Global Market Intelligence, hardly anyone believes Clean Energy will turn profitable before 2021 at the earliest -- which may be longer than a lot of investors want to wait for more good news.

Given this, it's really not surprising that some investors might want to bank some of yesterday's gains. They may think they can just wait for a lower stock price to buy back in -- and thanks to today's decline, that lower stock price has already arrived.