Report: 8 more power plants needed

Offering some new numbers about New England's projected need for more electricity, the region's power-grid manager said yesterday roughly eight big power plants and over $3.5 billion in high-voltage transmission improvements need to be in place by 2015.

A new report by Independent System Operator New England , the Holyoke organization that manages the six-state power grid and wholesale electric markets, also warns that the region has become too dependent on natural gas for producing electricity.

Following the approval of a spate of new gas-fired power plants in the late 1990s, New England now gets about 40 percent of its electricity from gas.

That represents "a serious reliability risk to New England customers, especially during winter peak-demand periods" when the region may risk not having enough gas for both heating and electricity production, according to the report, an updated 10-year outlook.

Between now and 2015, average electric demand in the region is forecast to grow 1.9 percent every year, or a total of 5,000 megawatts, comparable to eight times the output of the Pilgrim nuclear generating station in Plymouth or three times the multi-unit Mystic generating complex in Everett .

ISO officials said one bright spot is that in the last 16 months, investors have submitted proposals for more than 35 new power plants around New England.

Also, five big high-voltage transmission upgrades costing over $2 billion are now underway, including a new $217 million Stoughton-to-South Boston supply line set to be activated by December, and power lines in Fairfield County, Conn.

But another $3.5 billion worth of work needs to be done in the next nine years, ISO said, to ensure power grid reliability and to remove bottlenecks.

Seth Kaplan , a senior attorney with the Conservation Law Foundation, a Boston environmental group, said he was pleased that the report commends expanded efforts to promote reductions in electricity use and improved energy efficiency as cost-effective ways to generate power.

Just a 5 percent cut in electric demand during summer and winter wholesale price spikes, the report said, would save New England consumers $490 million annually.

Also, Kaplan said, the report indicates the new line from Stoughton will improve Boston electric supply enough that controversial plans won't be necessary for new plants, including proposed diesel units in Chelsea.

The ISO report endorses efforts to find someplace in New England to build non-gas "baseload" power plants that would run virtually continuously.

Material from Globe wire services was used in this report. Peter J. Howe can be reached at howe@globe.com.