June 11 (Bloomberg) -- Plug Power Inc., a maker of fuel cells that's never made a profit, plans to fire 21 percent of its workforce in a shift from engineering and development to marketing and sales of the battery-like systems.

Plug will offer severance packages to the 80 affected employees, who are mostly from headquarters in Latham, New York, the company said today in a statement.

Fuel cells, once thought to become ubiquitous sources of electricity in cars and homes as a pollution-free power source, failed to gain traction as solar, wind and other renewable energies became cheaper. Except in parts of California, a delivery system was never developed for hydrogen, the most common fuel source.

Plug fell 12 cents, or 4.6 percent, to $2.50 in New York Stock Exchange composite trading. The shares have dropped 37 percent this year. Plug shares were initially offered at $15 in October 1999, and reached a record $149.75 in six months.

Plug was formed by Michigan utility-owner DTE Energy Co. and Mechanical Technology Inc. to develop and produce a fuel- cell system to light homes and small businesses with a sophisticated battery. DTE holds 9.1 percent of Plugs shares.

To contact the reporter on this story: Christopher Martin in New York at cmartin11@bloomberg.net.

Last Updated: June 11, 2008 16:23 EDT