What happened

The sun is shining brightly on solar stock investors Wednesday, with shares of solar panel installer SunPower (NASDAQ:SPWR), solar module-maker JinkoSolar Holding (NYSE:JKS), and solar inverter inventor Enphase Energy (NASDAQ:ENPH) all soaring more than 10% in morning trading. As of 12:45 p.m. EST, SunPower stock was still up 9.8%, Jinko was up 11.2%, and Enphase was up 9.1%.

Why? That's something of a mystery.

Long line of solar panels laid out at sunrise looks like a road leading directly to the sun

Image source: Getty Images.

So what

None of the usual catalysts for big, 10%-plus stock moves are apparent today -- no analysts are upgrading solar stocks nor raising price targets on the same. None of the three have announced earnings -- or really announced much of anything at all.

The closest thing I see to a catalyst for today's stock price gains is the fact that, back on Monday, Goldman Sachs raised its price targets on two of the three stocks named, positing a $23 target price for SunPower and a $127 price for Enphase, according to TheFly.com.

Now what

Goldman Sachs' comments accompanying those two price target hikes may provide a clue as to why solar stocks continue to show strength today. At the time, Goldman cited "President-elect Joe Biden's proposed clean energy policies" as its greatest reason for optimism in the solar sector, and predicted that investors will see faster deployment of solar panels in coming years.

Assuming Goldman Sachs is right about this, of the three stocks named, I have to conclude that Enphase is the best way to play the trend -- because of the three stocks named, it's the only stock that is currently generating cash from its business. According to data from S&P Global Market Intelligence, over the past 12 months, both SunPower and Jinko have reported burning cash. Enphase, in contrast, has generated a total of $215 million in positive free cash flow.

Granted, investors can have differing opinions on whether even $215 million in FCF justifies a $15.5 billion market capitalization for Enphase (it works out to a 72 times multiple to FCF). But beggars can't be choosers. Of the three stocks named, Enphase is the closest thing we've got to a stock trading for fair value -- even if it isn't really close at all.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.