New England passes its 100th duck curve day of 2024

For the 100th time this year, demand for electricity from New England's power grid was lower at midday than overnight, a sign of significant growth in behind-the-meter solar photovoltaic power in recent years. Until 2018, this phenomenon -- called the "duck curve" due to the shape of graphs of demand -- had never occurred. But according to the region's grid operator, duck curve days will likely continue to recur.

ISO New England says that April 21, 2018 was the first day when "New Englanders used less grid electricity midday than while they were sleeping". Nearly two years later, by the spring of 2020, the duck curve phenomenon had appeared on seven days. By the end of 2021, it had occurred a total of 35 times.

The duck curve phenomenon has since gone from rare to common. The grid operator says there were "45 times in 2022 when demand for grid electricity was lowest during the day instead of at night." In 2023, New England experienced 73 duck curve days. Last year the region also set a new low for midday demand, thanks to mild temperatures, a holiday, and continued growth of behind-the-meter solar.

The duck curve trend has continued to spread. According to ISO-NE, "the region recorded its 100th 'duck curve' day of 2024 on Monday, November 25."

Graph from ISO-NE. Available at 100th ‘duck curve’ day marks New England solar power milestone - ISO Newswire

So far this year, the New England grid has also set a new record low for midday demand. 

The grid operator notes:

Duck curve days are becoming more frequent as more New England homeowners and businesses install solar power systems. But duck curves are not disruptive from a grid operations perspective. Staff in the ISO’s control room keep the entire system in balance by instructing the region’s other energy resources to decrease production when BTM PV output is high, and to increase production when BTM PV output is low. 

At the same time, this level of solar penetration requires flexibility from "the region's other energy resources", which must be technically capable of ramping up and down to follow load, as well as economically capable of sustaining commercial operations.