After Plug Power went public in 1999 its stock skyrocketed, reaching $150 a share before beginning a long decline in 2000; today it trades at less than $4.

Certainly not Michael M. Walsh, a mechanical engineer who is a consultant to Plug Power, the company running the Latham test.

Detroit Edison, a part-owner of Plug Power, plans to purchase 30,000 to 50,000 units.

But the run-up hasn't provided nearly as much lift as one might expect for two companies that, together, hold an enormous stake in Plug Power.

DTE Energy, a Detroit utility, and Mechanical Technology of Albany both helped to found Plug Power; each continues to hold a 32 percent stake in it.

And investors are getting a stake in Plug Power that is worth $1.66 billion at current prices, amounting to more than a third of DTE's market capitalization.

And he said many people in the area have invested in Plug Power and Mechanical Technology.

It is also operating a compact hydrogen refueling station in nearby Latham, at the headquarters of Plug Power, a fuel-cell company.

Mr. Tomson is expected to leave Plug Power.

In 2007, the company was sold to Plug Power for $10 million.