The first liquefied natural gas facility built on the East Coast in about 30 years opened for business yesterday as a tanker began offloading its cargo at a pipeline in Massachusetts Bay, about 18 miles east of Boston.

Carrying about 1 billion cubic feet of liquefied natural gas, or LNG, from Trinidad, the ship Excellence became the first to use the deepwater port completed at the end of last year by Excelerate Energy LLC of Houston. Unlike other tankers which deliver liquefied natural gas to storage facilities where the LNG is reconstituted as gas for pipelines, Excelerate's tankers return LNG to its gaseous form on the ship and pump it directly into the pipeline.

The Massachusetts facility, known as the Northeast Gateway, is one of only two of its kind in the world, the company said. The other is also owned and operated by Excelerate in the Gulf of Mexico.

The opening of the facility, which has the capacity to handle up to 500 million cubic feet a day, or about 20 percent of New England's average daily use, provides another source of natural gas to meet the region's growing appetite for the fuel. Natural gas is used to generate about 40 percent of the region's electricity and heats 44 percent of homes in Massachusetts, compared to 39 percent that use heating oil, according to the Energy Department.

The offshore facility also could help avoid shortages and price spikes during cold winters and hot summers, or when other sources are disrupted, such as the shutdown of Gulf pipelines after Hurricane Katrina in 2005.

"This is an important new source of natural gas delivered by an innovative technology," said Secretary of Energy and Environmental Affairs Ian Bowles. "The additional supply should ease concerns about shortages during the winter months, and offshore delivery poses fewer security and environmental issues than onshore LNG facilities."

The amount of natural gas Excelerate will bring to New England will depend on demand and prices, said Doug Pizzi, a spokesman for the company. Excelerate, teaming up with pipeline company Spectra Energy of Houston, invested some $350 million to extend Spectra's local pipeline and develop the deepwater port.

The port uses two loading buoys located about 90 feet below the surface. When a ship comes in, it draws one of the buoys up to the ship, where it is connected to the regasification equipment.

Excelerate first proposed the project in 2004 and began the permitting process about a year later. The company received its license last May and completed construction in December.