New England’s grid is undergoing a rapid change as nuclear, oil, and coal-fired power plants that operate with stored fuel are retiring in larger numbers, and are being replaced by natural-gas-fired plants and renewable generation. Natural gas accounted for 49 percent of the region’s power generation last year, up from just 15 percent in 2000. While constrained pipelines and fuel delivery logistics challenge the timely supply of natural gas, wind and solar power are influenced by weather patterns. This impedes the ability of power plants to obtain the fuel they need to run, thereby posing reliability risks.