Renewable energy stocks surged higher Tuesday after Plug Power (PLUG -9.82%) announced receipt of a $1.66 billion loan guarantee from the U.S. Department of Energy. Plug currently has two hydrogen fuel facilities producing at full capacity, with a third approaching that mark. Plug says the government assistance will help it to "finance the development, construction, and ownership of up to six green hydrogen production facilities" -- although it's not 100% clear whether it was including its first three facilities in this tally.

Either way, Plug's news inspired investors to snap up shares of similar green energy stocks that might be able to attract some federal assistance of their own. As of 1 p.m. ET, shares of FuelCell Energy (FCEL -4.99%) stock were up by an astounding 32.4%, and Bloom Energy (BE -7.47%) gained 7.9%. Clean Energy Fuels (CLNE -1.90%), which provides renewable natural gas and filling stations for alternative-fuel heavy vehicles, was up by 10.5%.

Plug's plans

Plug hailed the Department of Energy award as "a major milestone in the U.S.'s commitment to advance the development of large-scale hydrogen production, processing, delivery, and storage," saying it "also underscores the application of green hydrogen to help meet decarbonization goals across multiple sectors of the economy."

This doesn't guarantee that other loan subsidies for its peers are in the offing. But it does suggest Plug's award is part of a larger policy that could benefit FuelCell, Bloom, and Clean Energy Fuels.

Should you buy FuelCell, Bloom Energy, or Clean Energy Fuels?

That being said, it's worth pointing out -- and repeating -- that despite nearly three decades of investing in fuel cell technology, Plug Power has never earned a profit from selling hydrogen fuel or hydrogen fuel cells. According to historical data from S&P Global Market Intelligence, Bloom hasn't turned a profit either, while FuelCell Energy hasn't earned a profit since 1997. Clean Energy earned a profit in 2017... but never since.

Maybe government-subsidized loans will help them change that story. Maybe they won't. But I wouldn't buy until I know for sure.