HARTFORD — New England’s power system is increasingly shifting from aging oil- and coal-fired plants and to natural gas that relies on pipelines experiencing bottlenecks that drive up prices, the region’s electric grid operator said Wednesday.
ISO-New England officials said wind and solar resources are a small but growing part of the region’s energy mix, though they are not always available when needed by the region’s 14 million residents — peak demand for power in winter typically occurs after the sun has set.
In contrast to last winter’s extended cold weather that pushed up energy demand and prices, a mild winter and falling oil prices this year have helped keep prices down. But winter has eight weeks to go and use could spike with a more traditional New England winter.
Natural gas pipeline bottlenecks are a continuing problem.
‘‘There’s plenty of natural gas,’’ said Gordon van Welie, president and chief executive officer of Holyoke, Massachusetts-based ISO-New England. ‘‘The problem we’ve had in the region is we’ve not matched the need for natural gas with infrastructure.’’
The proportion of natural gas in the region’s energy mix was 44 percent in 2014, up from 15 percent in 2000. At the same time, coal- and oil-fired generation dropped to 6 percent from 40 percent.
As much as 8,300 megawatts of older coal- and oil-fired generating capacity could be at risk of retirement due to economic pressures and potentially more stringent environmental rules. If those 28 generators retire, 6,300 megawatts of new or expanded capacity would be needed to replace them.
Plant retirements underway include Salem Harbor Station, Brayton Point, and Mount Tom Station in Massachusetts, Vermont Yankee and Norwalk Harbor in Connecticut.
Proposals for 9,500 megawatts are seeking to be connected to the regional grid, but much of that may not pan out and some plans are for wind power in remote areas of northern New England that transmit energy that cannot reach southern New England. Billions of dollars would be needed to extend transmission to the remote areas, ISO said.
New England could operate solely and reliably on natural gas, but only if pipelines are ‘‘robust enough to meet demand’’ and if sufficient local storage of gas is available, van Welie said.
The region has benefited from $7 billion in transmission system upgrades since 2002, with an additional $4.5 billion expected through 2018, grid officials said.