The summer months of June, July, and August are when we typically expect the annual system peak to occur. Since the early 1990s, New England has been a summer-peaking region, and we have relied on that to estimate when the peak may hit. However, the summer of 2023 threw us a curve when the peak occurred on September 7.

What has changed the timing of the Annual System Peak?

Behind-the-meter (BTM) solar generation. While BTM solar is pushing the peak later in the day, it may also be affecting what month it occurs. ISO-NE estimates about 7,000 MW of BTM solar generation. That takes a significant amount of power off the grid in the middle of the afternoon in the summer. As we enter late August and the sun begins to set earlier, reducing solar generation, an early-September heatwave combined with lower solar production can result in a September peak.

Weather will continue to be the main factor; hot and humid days are prime candidates for the peak. But weather patterns are changing as well, adding to the complexity of predicting the peak. The move toward electrification is also affecting demand.

As indicated below in Figure 1, annual electricity use has gradually declined over the past 20 years, but the annual system peak has remained relatively consistent.

Powering the Grid

ISO-NE continues to plan for various scenarios to ensure that there is adequate supply to meet summer demand. Although they expect adequate supply this summer, they can also import power from neighboring regions to mitigate unexpected generator outages or transmission issues.

ISO-NE’s Summer Expectations

• Peak Demand Forecast – Typical Weather – 24,553 MW
• Peak Demand Forecast – Above Average Weather – 26,383 MW
• Available Capacity – More than 30,000 MW
• Highest Annual System Peak – 28,130 MW

Through the beginning of June, there was yet to be a day that came close to a peak based on historical peaks. Then came the week of June 17, with three days of intense hot weather in the Northeast, including two potential peak days, June 19, and June 20. The weather in New England is notorious for changing rapidly, and with the weather becoming more volatile, we continually expect that a potential day can arrive unexpectedly.

If you are subscribed to our Peak Notifications, expect to see notices that will recommend curtailment between 4-7 pm, but please be aware that could change with data and information from ISO-NE and weather conditions. 2022 is an example of the surprises that can show up; the peak occurred from 3-4 pm. We will continue to notify with as much advance notice as possible.

To subscribe to Freedom Energy’s Peak Notification Program, please complete the form here.

Have any questions, contact Howard Plante at howard.plante@felpower.com.