ISO-NE expects minimal power system impacts from partial solar eclipse

A partial solar eclipse is expected to cause a noticeable but manageable reduction in output from New England’s behind-the-meter photovoltaic (BTM PV) resources on Aug. 12.

While eastern Greenland will experience a total eclipse, the phenomenon will be less noticeable in New England. The moon will cover about 23% of the sun as seen from northern Maine, dropping to about 10% in southwest Connecticut.

ISO New England estimates BTM PV output could be reduced by 600 to 800 megawatts (MW) during the eclipse, depending on the amount of cloud cover and wildfire smoke. The effects will be most pronounced around 2 p.m.

BTM PV includes smaller-scale systems connected directly to retail customers or to local utilities and not the regional power system operated by the ISO. BTM PV reduces the amount of demand on the grid when the sun is shining.

ISO-NE operators have extensive experience managing the grid through situations where demand dips and spikes, such as during previous solar eclipses. Operators can account for the sudden changes in BTM PV performance by instructing other generators to increase or decrease output appropriately.

The 2026 eclipse will have a significantly smaller impact than one on April 8, 2024. During that event, portions of northern New England experienced a total eclipse and BTM PV generation dropped by over 2,800 MW.