What happened

A broad-based stock rally, fueled by positive coronavirus news (a new steroidal treatment) and renewed promises that President Donald Trump will deliver on his four-year-old pledge to spend $1 trillion on infrastructure, is lifting stocks of all stripes today. The S&P 500 is up a respectable 2%, and individual companies within the renewable energy sector are doing even better.

In 2 p.m. trading, we're seeing shares of solar microinverter-maker Enphase Energy (NASDAQ:ENPH) up 7.6%, and Livent Corporation (NYSE:LTHM), which mines lithium used in the rechargeable batteries that store solar power, up an even more impressive 10.5%. Elsewhere in the sector, fuel cell pioneer Plug Power (NASDAQ:PLUG) is enjoying a solid 6.4% gain.

Collage of windmills, solar panels, and electric lines representing the renewable energy industry

Image source: Getty Images.

So what

What's driving these stocks up, aside from general bonhomie over the coronavirus-cum-stimulus news today?

In the case of Livent, and to an extent perhaps Enphase as well, I believe what we're seeing is part of a general rising optimism about the future of solar energy -- and solar stocks. The remarkable popularity of Nikola's (NASDAQ:NKLA) start-up electric truck company probably has a lot of momentum traders looking for the "next big thing" in electric power. Because electric cars and trucks require lithium to form their batteries, and solar power to generate (some of) the electricity they run on, Livent and Enphase would seem to be logical beneficiaries of this enthusiasm.

Now what

The run-up at Plug Power is more of a mystery to me.

In contrast to Enphase and Livent, both of which have generated positive profits over the past year, and both of which are (according to analysts polled by S&P Global Market Intelligence) expected to continue earning profits for the next several years at least, Plug Power "boasts" an uninterrupted history of losing money for the past 23 years straight -- and is expected to lose more money this year, next year, and the year after that.

While I might quibble with investors bidding up shares of Livent and Enphase so much today, and on mostly tangential news, at least these are solid businesses with solid histories of profitability behind them, and good prospects ahead of them.

In contrast, I see no good reason why Plug Power should be going up 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.