A Total Eclipse Over MISO
Preparing the grid for a rare astronomical event 
Alexandra Andrzejewski - 04/02/2024

Millions across the MISO footprint, including an influx of travelers, will turn their eyes to the sky on Monday, April 8. That's when the moon will slide in front of the sun, causing its outer atmosphere to glitter into view. While millions look up to watch the light go out, MISO’s operators will keep their heads down to make sure your lights stay on. We don’t expect any reliability-related issues, but we’ll be prepared for anything. 


2017 was the last time the path of a solar eclipse crossed the MISO region. Back then, MISO had about 100 MW of available solar generation. Today, there is more than 5,000 MW. That's a big change and the reason our operations team is busily preparing for April 8.  


When and where 

The path crosses our South and Central regions to include parts of Arkansas, Missouri, Kentucky, Illinois and Indiana. Two of our control centers (Carmel, Indiana and Little Rock, Arkansas) fall in the path of totality. We expect to see shifts in darkness occurring from 1:30 to 4:25 p.m. ET. 


How an eclipse impacts reliability planning  

Solar eclipses create a rare challenge when it comes to balancing electricity supply and demand. That’s because of the potential for a steep decline in solar generation as the darkness slides in and a steep rebound once the eclipse passes, as shown in the graph.  


Forecasting demand for a typical day is typically straightforward; however, April 8, will not be a typical spring day. Schools will be closed. Businesses may change their routines. More people will be at home. Hotels and restaurants will be busier than usual due to the expected influx of tourists. And temps could be cooler because of the darkness. These factors make it more challenging to accurately forecast electricity demand for the day. But MISO operations is evaluating risk from every angle. 


“Each critical event tends to bring a unique set of risks to manage the system reliably and efficiently, and we expect this eclipse to be no different,” said Jason Howard, director, operations risk management. “The 2017 and 2023 eclipses were great warm-up drills, and our team is committed to ensuring our control centers have the information they need to reliably manage our footprint.” 


How we’re preparing 

Each day leading up to the eclipse we will continue to hone our forecasts. The control room team working on April 8 is focused on managing the uncertainty and variability.  


“The uniqueness of this solar eclipse requires extra planning and coordination between our operators and support staff,” shared Christopher Coyne, the shift manager who will be in charge on April 8. “By leveraging our technical expertise and the flexibility of our market design, we will be prepared to reliably deliver power to our customers during this rare event.” 


To ensure reliability and hedge uncertainty, MISO plans to increase reserve requirements for April 8. Operations will also line up extra generation that can come online quickly if needed. MISO will ask members to hold off on solar testing during the eclipse. 


The bottom line 

MISO's operation team is working hard to prepare for the great eclipse of 2024. We do not anticipate any eclipse-related reliability issues in our region. The big unknown is the role Mother Nature will play on April 8. A sunny, cloudless day could result in an estimated 4 GW drop in generation over the course of 90 minutes. And a 3 GW rebound. Clouds will lessen those numbers.  


Either way, when the time comes, grab your eclipse glasses and head outside. Watch in wonder as your world goes dark. And remember, while the sunlight is interrupted for a few minutes, our operators will make sure your electric power isn’t.