New England's energy grid operators say while the region increasingly banks on reliable clean energy, constraints in natural gas pipelines could bottleneck power supply by the winter of 2024-25, potentially leading to higher energy prices and risking the system's reliability.

ISO New England, which operates the regional grid and runs the wholesale energy market, recently released its annual report, laying out a future when technological advances, declining costs and state and federal initiatives are boosting renewables, energy storage and efficiency.

But renewable fuel sources currently are dwarfed by natural gas, which provided more than 40 percent of the region's electricity last year, ISO New England said.

Natural gas pipelines continue to be constrained, especially during stark New England winters, the report argues. The strain on fuel supply comes at a time when other power sources are shuttering: more than 4,600 megawatts from oil, coal and nuclear plants like Pilgrim Nuclear Generating Station will have retired from 2013 to 2021.

"The biggest challenge to the reliability of the grid is the lack of fuel infrastructure to supply the fleet of natural gas-fired generators," ISO New England's board Chairman Philip Shapiro and President and CEO Gordon van Welie wrote in the annual report. "In the coming years as more oil, coal and nuclear leave the system, keeping the lights on in New England will become an even more tenuous proposition."

Another 4,000-plus megawatts of new natural gas-fired plants are proposed throughout the region, presenting grid operators even more infrastructure challenges over the next few years.

Anne George, ISO New England's vice president of external affairs, said while many companies were vying for transmission projects, including efforts to bring Canadian hydropower to the region, there "really are no active pipeline proposals right now."

"Various states have tried different tactics, but they've all been stymied," George said. "We continue to raise the issues and the potential reliability impacts from it. But the region is struggling with how to move forward."

'We're at the end of the pipeline'

The annual report highlights an ISO New England study released in January that analyzed 23 possible future resource and fuel scenarios, and found that by the winter of 2024-25, "inadequate fuel supply would lead to energy shortfalls in almost every scenario," leading to emergency actions or reliability events like rolling blackouts.

Shapiro and van Welie said ISO New England can mitigate fuel security risks by strengthening "financial incentives for power plants to secure more reliable wintertime fuel arrangements," but the onus is primarily on state officials and generators in the market to bolster supply or boost infrastructure.

Eric Brown, senior counsel for the Connecticut Business and Industry Association, said the lack of natural gas infrastructure leads to greater reliance on oil and coal during harsh winters, paired with higher demand and prices.

"There's just not the capacity. It's economics 101," Brown said, calling on New England leaders to move beyond politics and help create solutions. "It's clear we're going to be highly reliant on (natural gas) for some time, so it's important to find a way to get infrastructure in place to avoid (rolling blackouts) that almost happened a few short weeks ago during the recent cold snap."

Mitch Gross of Eversource Energy agreed the constraints hit supply and prices hardest in winter.

"Here in the Northeast, we're at the end of the pipeline, whether it's natural gas or oil, so the transportation costs to get that fuel here drives prices up," Gross said.

Enbridge Inc. had proposed the Access Northeast pipeline project, which the company says would provide "a critical opportunity to improve New England's future energy reliability, cost volatility and competitiveness."

But last year the company suspended the project, saying New England states must align on legal and energy policy to see the pipeline come to fruition.

Wind power surpasses natural gas proposals for first time

ISO New England noted that new wind power projects seeking connections to the grid outnumbered natural gas proposals for the first time in 2017.

Wind proposals, largely in Maine or offshore Massachusetts, total about 8,500 megawatts of new power, about double the amount proposed in natural gas generation.

Some advocates push for much greater investment in renewables instead of new pipelines.

Claire Coleman of Connecticut Fund for the Environment pointed to studies by Synapse Energy Economics arguing ISO New England based its analysis on extreme scenarios, including record-breaking cold and the shutdown of major power facilities like the Millstone Power Station.

"Extreme, worst-case scenarios should not be the basis of our region's energy policy," Coleman said. "Renewable energy growth and increased energy efficiency must be properly taken into account when assessing our region's energy reliability and developing supportive policies."

Coleman noted Synapse Energy Economics' conclusion that pushing for greater infrastructure "disregards New England's decades-long and highly successful efforts to improve the efficient use of gas and electricity and develop alternative resources to reduce fossil fuel emissions."

Dan Dolan, president of the New England Power Generators Association, disagreed with the notion that the recent cold snap was proof greater infrastructure is required.

"Some of the older oil facilities that hardly ever run were running during that period of time, exactly when we needed them to," Dolan said. "That's why those plants are still around, for the once-in-a-100-year cold snap. The owners had been making the investments in upkeep at those facilities so they were able to run even in sub-zero temperatures, and we didn't have any reliability events."

Dolan said while harsh winters offer lessons on what improvements can be made, New Englanders and policymakers should "acknowledge we have a system that drives the lowest wholesale prices in history, billions of dollars in new plants and investments, and the lowest carbon emissions of any sector."

George, of ISO New England, countered that the recent low temperatures mirrored some of the scenarios in the organization's January study, complete with spikes in prices and oil supplies stretched to the limit.

"Granted, we didn't see any reliability events, but only because there was a lot of discussion and coordination with our operators and other entities in the marketplace," she said. "We were pleased we didn't have any reliability issues, but it wasn't this smooth operation and it reinforced our concerns."

ISO New England noted the regional transmission system — about 9,000 miles of high-voltage transmission lines and 13 interconnections to New York and Canada — has continued to see improvements.

Investments in transmission projects, ultimately funded by the region's ratepayers, have led to less air pollution and fewer blackouts, the report said.

As of January, more than 20 transmission upgrades have been proposed across the region that will help deliver clean energy from northern Maine, New York and Canada.

b.kail@theday.com