BOSTON – New England will not have enough natural gas to heat homes and generate electricity if more pipelines aren’t built before winter 2003, according to a new report issued Monday.

The report said the region is unlikely to suffer California-style electric outages, but it said private companies need to spend hundreds of millions of dollars on new pipelines or else the construction of new power plants that use natural gas will be wasted.

Most of the region’s power plants now rely on nuclear power, coal or oil to produce electricity, but natural gas is rapidly gaining.

In 1999, it was used to generate 16 percent of the region’s electricity, but by 2005, natural gas will be used to generate 45 percent of the electricity, according to the report.

But the region’s existing network of pipelines won’t be able to transmit that much natural gas, especially from November to March, when gas is used to produce electricity and to heat people’s homes.

“We simply don’t have the capacity, starting in 2003 – and it gets worse after that – to keep the plants on line during the peak days of winter,” said Stephen G. Whitley, vice president of ISO New England, the independent company that oversees the region’s electricity grid.

New England gets its natural gas through five interstate pipelines that transmit gas from the Gulf Coast of Louisiana and Texas, from western Canada, and from Sable Island, off the coast of Nova Scotia.

Tankers also bring liquefied natural gas from Trinidad into Everett, north of Boston.

About 2,200 miles of natural gas pipelines already exist in New England.

But Richard Levitan, president of the firm that prepared the report for ISO New England, said another 50 or 100 miles will be needed by 2005 to carry enough natural gas to satisfy regional demand.

Anita Flanagan, spokeswoman for the Shelton, Conn.-based Iroquois Pipeline Operating Co., said it’s one thing to propose new pipelines, but quite another to actually build them.

Cost is one obstacle. Iroquois, which transmits gas from western Canada through New York to most of New England, is building a 32-mile pipeline from Long Island to the Bronx that will cost $173 million.

Environmental permitting processes are another. Local, state and federal reviews can delay plant construction for years, said Flanagan. Iroquois’ Bronx pipeline was proposed in April 2000, but if all goes as planned, it won’t open until late 2002.

“It’s not a matter of deciding one day that it’s a great idea, and then going out the next day and doing it,” said Flanagan.

But ISO Chairman William Berry said companies are finding it profitable to use natural gas to produce electricity because it’s more efficient and cleaner-burning than oil or coal.

That’s why power plants built recently in Dighton and Tiverton, R.I., and those under construction in Everett and Southbridge are all gas-fired, Berry said.

Across New England, about 20 new power plants are proposed or under construction, with nearly all of them relying on gas, according to the Conservation Law Foundation.

The competition among those power plants – and the surplus power production potential – are the main reasons New England won’t undergo the same electrical power outages that have plagued California, energy officials said.

If the gas pipelines aren’t built quickly enough, some New England power plants will also be able to burn oil to generate electricity, though Levitan said the pipelines would ensure that consumers wouldn’t face “fantastic blowouts” in their electric bills.