The Eclipse Will Be a 3-Hour Boon for Gas, Batteries, and Hydro

Early April is typically a kind of goldilocks moment for solar power. Days are getting longer but the weather is still mild, meaning that higher solar power generation isn’t entirely eaten up by increased demand due to air conditioning.

But that all depends on the sun actually shining.

Today’s solar eclipse will take a big chunk of power off the grid. Since 2017’s eclipse, solar power generation has increased substantially, both locally (think rooftops) and at utility scale (think massive fields of solar panels). In 2017, the U.S. had around 35 gigawatts of utility-scale solar capacity, a figure that had increased to an estimated 95 gigawatts by the end of 2023.

While total solar eclipses are rare (the next one to hit the lower 48 isn’t expected until 2044 ), the challenges they present to grid operators may be part of the new normal. With vastly expanded renewable energy generation comes a greater degree of unpredictability, as a growing a portion of the generation fleet can drop off the grid due to weather and climate conditions — like, say, clouds of smoke from a wildfire — that cannot be precisely predicted by 17th century science. So while grid operators are confident they’ll be able to manage through today’s eclipse without any reliability issues, the stakes are higher.

In Texas, the eclipse means that as much as 17 gigawatts of generation could fall off the grid, while in the PJM Interconnection , which includes parts of Ohio and Pennsylvania that are in the path of totality, some 4.8 gigawatts of utility solar may disappear.

The Midcontinent Independent System Operator, which includes a swath of the middle of the country from Minnesota to Indiana to Louisiana, the amount of utility-scale solar has increased by an order of magnitude, going from around 100 megawatts to around 5,000 . In that grid, operators say that the drop off in power could be as much as 4 gigawatts, with three coming back as the sun returns later in the day.

Overall, the U.S. Energy Information Administration estimates that some 6,500 megawatts of solar generation capacity will be fully obscured during today’s eclipse, and that the eclipse will “partially block sunlight to facilities with a combined 84.8 GW of capacity in an even larger swath of the United States around peak solar generating time.” Some 40 gigawatts could come off the grid, enough power for about 28 million homes, according to a release from Solcast, a solar forecasting company.

By comparison, during the 2017 eclipse, solar power loss at its peak was between 4 and 6.5 gigawatts and the total loss of power was around 11 gigawatts, according to the National Renewable Energy Laboratory.

In states like Texas, the main effect will be on the utility-scale production of solar, but in the Northeast and parts of the mid-Atlantic and Midwest, there will be a related problem: Behind-the-meter solar will fall off, too, thus requiring the homes and businesses that generate power for themselves in the middle of the day to get more power from the grid. This has the effect of increasing demand on the grid at a time when overall supply is down.

In New England, which has seen immense growth in rooftop solar, solar production is expected to fall by “thousands” of megawatts, according to ISO New England, while the New York Independent System Operators expects to lose 700 megawatts of behind the meter solar.

During the 2017 eclipse, the National Renewable Energy Laboratory found that “the burden of compensating for the lost energy from solar generators fell to the thermal fleet,” i.e. natural gas, along with some increases in coal and hydropower production.

Since then, the coal fleet has shrunk, thus putting more of the burden of responding to today’s eclipse likely onto gas and hydro, but the basic logic still applies. “Grid operators are expected to rely on natural gas to ensure stability and meet the household demand spike across national grids, as was done during the previous eclipse in 2023 in California and Texas,” according to Solcast.

The Southwest Power Pool, which operates in much of the Great Plains, said that it has “ample generating capacity provided by other resources (e.g. coal, natural gas, wind, nuclear, hydro and others) to make up for any potential loss and expects modest demand for electricity that day.”

One other thing the grid didn’t have much of seven years ago: batteries. According to the EIA, battery storage has gone up from 600 megawatts in 2017 to around 15.5 gigawatts today. In California, which is outside the path of totality but is still expecting a substantial drop-off in solar power, the system operator “plans to use quick ramping energy, including battery storage, hydropower and natural gas plants,” to make up for lost power.

ERCOT, the electricity market that covers most of Texas, said in a presentation that it will rely on “ancillary services” — power sources that can respond quickly to immediate needs — which is where batteries are already doing the bulk of their business in Texas .

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