PORTLAND, Maine — A developer of tidal power in the nation’s northeastern corner is reporting success with its first commercial-sized underwater turbine, putting it on track to have one connected to the power grid by the end of 2011, officials said Wednesday.

Ocean Renewable Power Co. describes its proprietary 60-kilowatt turbine generator as the largest ocean energy power plant ever installed in U.S. waters.

So far, the unit has met or exceeded specifications for power in testing this year in the waters of eastern Maine, said Chris Sauer, president and CEO.

“It’s a critical step to our first commercial unit that’ll be connected to the grid in little more than a year now,” Sauer told The Associated Press. He touted the underwater turbine’s success as “a huge milestone for America’s ocean energy industry.”

The system will be fine-tuned before a 150-kilowatt system is installed by the end of next year, providing enough electricity for 50 to 75 homes, he said.

Ocean Renewable holds a license for three sites off Eastport, where twice a day the tide rises and falls 20 feet, making it one of the world’s best tidal power sites. Eventually, the company plans to deploy arrays of underwater turbine generators, producing more than 100 megawatts.

Maine is already New England’s leader for wind power generation. But Ocean Renewable sees big potential for tidal power in the coming decade.

Tidal power appeals because tides are predictable and water’s density means fewer turbines are needed to create the same amount of electricity as wind turbines. There also are none of the aesthetic issues associated with wind farms because the turbines are hidden underwater.

Also Wednesday, the company announced that it’ll move forward over the next two months with a demonstration project at the Coast Guard station in Eastport.

The 60-kilowatt unit will be used to charge a battery system that will provide supplemental power to the Coast Guard station, said Susy Kist, spokeswoman for Ocean Renewable. The project will be used to evaluate tidal power technology that the Coast Guard hopes to employ at isolated stations in Alaska.

“The Coast Guard in Maine encounters the power of the elements on a daily basis. Capturing some of these sustainable forces to help achieve our energy needs is a prudent and responsible thing to do,” said Capt. Jim McPherson, the Coast Guard’s northern New England commander.