Electricity demand, which tends to rise into the hottest part of a summer day, on Monday developed a weird U-shaped dip over a two-hour period across the country.

Grid operators and traders thought they were totally prepped for the historic US solar eclipse. There was just this one thing they didn’t completely factor in: “irregular human-behavior patterns.”

That was the technical definition from Southwest Power Pool, which manages a network stretching from North Dakota to Louisiana, for the conduct of millions of Americans who were outdoors watching the moon covering the sun instead of cranking up the A/C in homes and offices. Demand, which tends to rise into the hottest part of a summer day, on Monday developed a weird U-shaped dip over a two-hour period across the country.

This was bad news for traders who had bet that prices would jump as a large swathe of American solar-produced megawatts faded to black. “If anything, it was bearish from a trading perspective because people were more busy looking at the eclipse and talking about the eclipse,” said Tom Hahn, vice president of US power derivatives at brokerage ICAP Energy in Durham, North Carolina, in a statement to Bloomberg.

While that was the most dramatic case of a power-price retreat, there were noticeable dips elsewhere. Cloud coverage in places like North Carolina, Texas and New Jersey had reduced solar output before the eclipse anyway, limiting the magnitude of the loss.

Alphabet’s Net Labs unit, which deploys thermostats and other smart home technologies, drew more than 750,000 customers into its Solar Eclipse Rush Hour experiment to cut consumption, Bloomberg reported. Net Labs reduced power use by about 700 megawatts, helping to offset a 10,000-megawatt drop in solar power. In California, Nest and other partners worked with the state utility commission to cut consumption by about 1,500 megawatts.

For the Southwest Power Pool, electricity use came in 2,500 megawatts below the forecast, said Bloomberg. The dip was also “very evident” in New England, New York and the nearby 13-state grid managed by PJM. The network, the largest US grid, with 65 million people, saw demand fall by 5,000 megawatts, or as much as 3.8 percent, during the event.

The next total eclipse in the US will be April 8, 2024.

image: https://ny.curbed.com/maps/solar-eclipse-2017-map-nyc