New England’s power grid has now seen 500 “duck curve” days since 2018 as rooftop (behind-the-meter) solar continues to expand. The question now is how to change the system of charges and payments that were created for the old, one-way electric grid so that they encourage and reward home-grown local power production.
The 500th duck curve day – a day when power demand on the grid is lower at midday than midnight because all the rooftop solar reduces how much people need to get from power plants – happened on Sept. 21, reports ISO-NE, which runs the grid (read the report here). The first of these days happened in 2018, and more than 100 have happened in 2026.
The reason for the change? The huge growth in rooftop solar. About 7,000 MW of it is now installed in New England at the moment, capable of producing more than five times as much electricity as Seabrook Station on a sunny day. That figure has doubled in just a couple of years and will continue to rise.
Duck curves are great but they’re also a problem for the grid because they require a lot of non-solar power like gas plants to turn on as the sun sets, yet many power plants aren’t designed to turn on and off quickly.
Batteries are increasingly being used to reduce the extremes by storing electricity at midday and releasing it at twilight. Utility-scale batteries in California are now half the size of the New England grid, in terms of how much power they can release at once, and Texas isn’t far behind.
Different rate structures can also help. The wildest example of that is in sunny South Australia, where almost one out of every three houses has solar panels. They’re going to provide free electricity – yes, free – for several midday hours to encourage people to use more of that solar power and reduce the extremes of the duck curve.
I don’t think that’s going to happen in New England but it’s an indication that as the energy transition increases the value of local power, we’re going to have to change a lot of our practices in ways that seem slightly crazy.
