Prior to the early 1990s, New England was a winter-peaking region, meaning the annual system peak for electricity demand occurred during the winter months. Since then, the New England grid has shifted to a summer-peaking system due to the significant increase in air conditioning and reduction in electric heating. Over the past four decades, it was rare to see new building construction without cooling and dehumidification equipment. New heating system installations were primarily fossil fuel-burning equipment, mainly natural gas.

The New England grid is expected to shift back to a winter-peaking system by 2032, based on ISO-NE’s current studies, largely due to the electrification of heating demand. Additionally, during the same period, solar generation is expected to double from 6,000 MW currently to almost 12,000 MW, including behind-the-meter solar, helping to reduce summer demand on the grid.

• Peak demand on a typical summer day ranges from 17,500 MW to 22,000 MW.
• Since 2001, the annual system peak has averaged 25,200 MW.
• Highest annual system peak: August 2008 at 28,038 MW
• Lowest annual system peak: June 2017 at 23,508 MW

Figure 1 depicts the increase in heating and transportation electrification from 2023 to 2032.

Figure 2 illustrates an example of the effect behind-the-meter solar generation has on grid demand. On May 22, 2024, a relatively hot and humid day with temperatures in the upper 80s and dew points in the high 60s, solar was contributing approximately 5,000 MW of power during mid-afternoon, pushing the actual peak later in the afternoon.

Each year, we notify our customers during the summer months when a potential annual system peak is anticipated. Except for last year when the peak was on September 7, the peak occurred in June, July, or August. The increase in the electrification of heating demand will occur gradually over the next eight years, during which ISO-NE expects the grid to peak in the winter. As we transition to a winter peak, we will have to carefully consider the winter months as peak demand gradually increases and begins to equal summer peak demand. As demand increases to levels in January and February that we typically see in the summer, we may start sending notices in the winter months. Staying informed will help ensure you are always prepared for any changes in energy demand.

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