Summer 2024 Was One for the Power Grid History Books

Summer 2024 Was One for the Power Grid History Books

Grid Operators in Several Regions Kept the Lights on This Summer With More Solar, Storage, and Wind

Did you notice your lights stayed on and your air conditioner kept running all summer long?

The demand for electricity often reaches its highest levels during summer afternoons when many people are using their air conditioning. Historically, the bulk power system-the network of generators and transmission lines-has met this demand using generation from hydropower and fossil fuels, but last summer marked a new chapter in the power grid history books.

Regions across the country used more solar and storage to supply enough electricity to keep the lights and air conditioners working all summer long-even in regions with elevated risk of outage due to extreme heat.

"In summer 2024, grid operators in all regions maintained enough capacity to keep the lights on during periods of peak demand, even as they retired older generators, and an increasing number of regions used more solar and storage to meet peak demand," said Paul Denholm, senior research fellow at the National Renewable Energy Laboratory (NREL). Now that summer is over and data have been gathered, Denholm and team have released a new publication on how the grid performed from June to September.

How Did Grid Operators Do It?

The new report describes summer grid operations in several regions but focuses on ERCOT, or the Electric Reliability Council of Texas, because it is one of the fastest-growing regions in the country and experienced near-record peak demand in 2024.

An extended period of hot weather started in Texas in early August 2024 when average daily temperatures reached 102°F. Summer peak demand hit its maximum on August 20. During the hour of peak demand (4 to 5 p.m.), solar generated significant output: about 18 gigawatts or 21% of total generation. That is more than 50% what solar contributed during the hour of peak demand on the highest demand day of summer 2023, which is the result of ERCOT adding more solar capacity to the grid in the past year.

The significant solar output reduced the risk of an outage and the need for other generation to keep the lights on. The solar output also shifted the period of highest risk of outage from the afternoon to later in the evening (around 8 p.m.) and shortened the net peak demand period-when other resources need to contribute-to only a few hours. That made it easier for storage with just an hour or two of capacity to help meet peak demand, contributing 3.9 gigawatts.

Storage was also able to recharge thanks to solar and wind. In hot summers like 2024, nighttime demand is also high when storage would normally recharge. Solar generation in the late morning and wind generation overnight this past summer covered more of the off-peak periods, allowing storage to recharge for longer for lower cost.

Was This Summer a Fluke?

Summer 2024 demonstrated the ability of solar, storage, and wind to provide valuable capacity during summer peaks not only in Texas but also California and New England. In the coming years, even more of these resources are planned to be connected to the grid.

"The Texas weather really hasn't changed since last year, but the ERCOT grid has changed," Denholm said. "Most likely, summer 2024 was a look at future grid operations, and these resources will play a bigger role meeting peak demand."

Learn more NREL's grid reliability research and energy analysis research.