PORTLAND, Maine — With its federal license in hand, a Maine-based tidal energy company is ready to install its underwater power system for the first time on the floor of the ocean.

Ocean Renewable Power Co. aims to begin installation of its first grid-connected power unit in mid-March at a 60-acre site in Cobscook Bay at the nation’s easternmost tip.

The first unit capable of powering 20 to 25 homes will be hooked up to the grid this summer, and four more units will be installed next year at a total cost of $21 million for the project, said Chris Sauer, president and chief executive officer of the Portland-based company.

Eventually, Ocean Renewable hopes to install more units to bring its electrical output to 4 megawatts at sites off both Lubec and Eastport. Ocean Renewable holds permits for three sites in the area, one of the world’s best tidal sites, where twice a day the tide rises and falls 20 feet.

All told, the company sees up to 50 megawatts of tidal power potential in the Eastport and Lubec areas, enough to power thousands of homes, Sauer said.

“It’s never going to be the dominant power-generating resource in the state of the Maine, but it’s going to be a significant contributor,” he said.

The Ocean Renewable turbine generator unit self-starts when the tidal current reaches about 2 knots, and is designed to produce up to 180 kilowatts under ideal circumstances. On average, however, it’ll produce 60 kilowatts at the installation site in Cobscook Bay near Seward Neck in Lubec, Sauer said.

Once it’s completed, the full array of five of those turbine generator units will produce about 300 kilowatts under the pilot project license issued last week by the Federal Energy Regulatory Commission. The completed pilot project will produce enough electricity for about 100 homes.

A month earlier, FERC issued the first such license to Verdant Power, which hopes to produce tidal energy from New York City’s East River. Verdant’s tidal power design looks a lot like a wind turbine, only it’s underwater. Ocean Renewable uses rotating foils that lend the appearance of a manual reel mower for cutting grass.

Ocean Renewable starts work later this month with underwater installation of a heavy steel base, which will be about 100 feet down on the ocean floor. A turbine generator unit will be anchored to the base, with 60 feet of clearance between the device and the ocean surface at the low tide.

Previously, the company’s prototype was tested in the waters off Lubec and Eastport, but it was mounted on a barge and lowered underwater for testing.

The Coast Guard will set rules to ensure fishing and recreational boat can safely operate despite the presence a barge, platforms with cranes and boats with divers. The general contractor is Perry Marine & Construction.

Officials in Canada are watching the Maine project with interest. By 2014, Ocean Renewable and Nova Scotia-based Fundy Tidal Inc. hope to install the same units in waters off Nova Scotia, where Bay of Fundy offers even greater tidal power potential, officials have said.