Power struggle ends -- no Seguro BESS in North County

East County News Service

April 4, 2026 (Escondido) -- The developer of the Seguro Battery Energy Storage System has formally withdrawn its application to build one of the world’s largest lithium-ion storage facilities in the hills of North San Diego County.

The decision, confirmed earlier this week, marks the end of a three-year battle between developer AES Corporation and the unincorporated communities of Eden Valley, Harmony Grove and Elfin Forest.

While some BESS projects now have compartmentalization to reduce the fire risk to residents, large facilities in residential neighborhoods still pose risks for residents.

The Seguro BESS project entered the public planning and review phase in 2023, with a formal public review period starting in October 2023, and public scoping meetings and permit applications for the project shortly thereafter. AES conducted community workshops regarding the project in March, April and May 2024 to discuss safety and environmental impacts. The company had aimed for the facility to begin operating in late 2025.

Looking at the neighborhood

On its website, AES said it was "committed to being a good neighbor and partner to the communities where our projects are located," and supporting local contractors, community organizations and programs.

"AES is proud to partner with Palomar College, Escondido Education Foundation, San Diego Children’s Discovery Museum, Solana Center and Solutions for Change," according to its website.

Concerned residents in the area said that more than a land-use victory, the shelving of the project provides a reprieve from what some described as a "ticking chemical time bomb" in their backyards.

The proposed 320-megawatt facility would have been capable of powering 240,000 homes for four hours. However, its proposed location was a 22.5-acre site zoned for limited agriculture and surrounded by residential neighborhoods.

Unlike most BESS projects, which are typically tucked into industrial zones or retired power plants, Seguro was slated for a residentially focused area near Palomar Medical Center.

“The community spoke loud and clear about this,” said JP Theberge, a community leader and member of the Elfin Forest/Harmony Grove Town Council. “More than 5,000 signatures were gathered, and close to a thousand letters were submitted. We understand the importance of BESS facilities to our energy transition, but we must ensure that the safety of communities is taken into consideration.”

The project faced major pushback when Palomar Health and a nearby business park rejected essential easements. Without these, AES would not have been able to easily connect the facility to the San Diego Gas & Electric substation in Escondido.

Concerns around the state

The withdrawal comes at a time of heightened anxiety over battery safety.

The project’s critics frequently pointed to two catastrophic events that have redefined the conversation around lithium-ion storage -- the 2024 Gateway Fire in Otay Mesa that burned for nearly two weeks and the 2025 Moss Landing Disaster when a fire at a BESS released an estimated 25 metric tons of heavy metals into the surrounding environment, leading to long-term health advisories for Monterey County residents.

These events highlight the phenomenon of "thermal runaway," a chemical chain reaction where a single failing battery cell generates enough heat to ignite its neighbors, creating a self-sustaining fire that is nearly impossible to extinguish with traditional methods.

"The fires that erupt from lithium batteries are extremely toxic, hard to extinguish, and tend to last for several days spreading toxic fumes and depositing heavy metals for miles around," Theberge said.

For more information on BESS, visit the U.S. Environmental Protection Agency site here.