ISO-NE preparing for April’s total solar eclipse

ISO New England is taking steps to prepare the region’s power system for next month’s total solar eclipse, which is expected to reduce solar energy production by thousands of megawatts during the afternoon of April 8.

ISO New England operators are familiar with managing the grid through situations where electricity demand dips and spikes, such as previous solar eclipses. To help ensure reliability and keep supply and demand in balance, ISO forecasters plan ahead and chart out expected energy demand from the grid for each hour a day in advance. These daily forecasts take a number of factors into account, including the season, day of the week, time of day, weather, and special circumstances such as an eclipse. 

Map: NASA

In the United States, the eclipse’s path of totality, where the moon will completely block out the sun, spans from Texas to Maine, enveloping northern Vermont and northern New Hampshire from 2:15 to 4:40 p.m. ISO New England is collaborating with local utilities and neighboring grid operators to evaluate the expected conditions and potential impacts.

According to NASA, all parts of New England will see at least 80% of the sun blocked by the moon during the peak of the eclipse.

The vast majority of New England’s solar power comes from small-scale, distributed systems connected directly to retail customers or to local utilities and not the regional power system operated by the ISO. These systems reduce the amount of demand on the grid when the sun is up.

Unlike the sun setting at the end of the day, solar production is expected to drop off fairly rapidly over the course of the eclipse and will need to be replaced by other sources of power generation. The exact amount of additional generation needed will depend on cloud cover that day. Further, solar production will ramp back up as the eclipse concludes, meaning that additional generation will need to be carefully reduced to maintain system balance.

Even a partial eclipse can have a major and measured impact on the power system. For context, during the partial eclipse on October 14, 2023, the sun was only covered by 10% to 20% and resulted in a drop in solar production of several hundred megawatts.

Though not anticipated, ISO system operators have a number of tools available to handle any supply deficits caused by extremely high demand or a sudden loss of other resources.