As the global energy transition accelerates, Battery Energy Storage Systems (BESS) have emerged as the linchpin of a decarbonized grid. With utilities and developers racing to deploy massive, utility-scale storage projects to balance intermittent renewable energy, a critical question has lingered in the minds of regulators, insurers, and local communities: Is the technology safe?
A landmark report released by the Electric Power Research Institute (EPRI), titled Risk Factors and Failure Statistics of Lithium-Ion BESS, suggests that the narrative surrounding battery safety is undergoing a paradigm shift. Despite a meteoric rise in global installed capacity, the industry has achieved a 98% reduction in the annual failure rate of lithium-ion systems between 2018 and 2025. This achievement signals that the "growing pains" of the nascent energy storage sector are being systematically addressed through engineering rigor, standardized safety protocols, and a culture of continuous improvement.
The Data: A Statistical Leap in Reliability
The figures provided by EPRI are nothing short of remarkable. In 2024, the institute tracked 26 battery storage failures worldwide against a backdrop of 343 GWh of cumulative installed capacity. By 2025, as global deployment surged to 634 GWh—nearly doubling the previous year’s total—the number of recorded failures actually decreased to 24. This represents a roughly 50% reduction in the annual failure rate in a single year, even as the scale and energy density of the projects grew significantly.
The United States has mirrored this global trend. From an early peak in failure rates, the U.S. has seen a 97% decline through 2025, even as domestic installations hit 149 GWh. This inverse relationship—where capacity rises while failure frequency plummets—is the strongest indicator yet that the industry is maturing.
EPRI’s research covers 150 significant thermal events recorded between 2018 and 2025, including fires, explosions, and electrical arc flashes. By analyzing these data points, researchers have been able to map the evolution of safety, proving that the risk profile of modern battery arrays is vastly different from the experimental systems of the last decade.
A Chronology of Progress: From Early Lessons to Modern Resilience
To understand how the industry reached this point, one must look at the historical context of battery deployment. The early years of lithium-ion adoption were characterized by rapid, often unstandardized expansion.
The Foundational Crises (2018–2020)
The industry’s safety journey began in the shadow of several high-profile incidents. A wave of battery fires in South Korea between 2018 and 2019, combined with a severe explosion at a utility-scale facility in Surprise, Arizona, in 2019, served as a "wake-up call" for the global energy sector. These incidents were critical diagnostic tools; they exposed fundamental weaknesses in thermal management, electrical protection, and, crucially, emergency response protocols.
The Era of Standardization (2021–2024)
Following the 2019 incidents, the regulatory and technical response was swift. Manufacturers began overhauling Battery Management Systems (BMS) to include more granular, real-time cell monitoring. Developers shifted their focus toward "defensive design," incorporating advanced fire suppression, improved ventilation, and more robust electrical isolation.
During this period, international standards began to crystallize. In North America, the development of UL 9540 and the National Fire Protection Association’s (NFPA) 855 standard provided a roadmap for safe installation and operation. The evolution of these standards, with the latest edition of NFPA 855 released in 2026, has essentially codified the lessons learned from the "trial by fire" of the previous decade.
The Maturity Phase (2025–Present)
By 2025, the industry moved from reactive safety measures to proactive, design-based reliability. Today’s projects are designed with "cascading failure" in mind, utilizing modular architecture and physical barriers that ensure if a single cell fails, the impact remains localized.
Supporting Data: Why Modern Systems Are Inherently Safer
The EPRI data suggests that modern battery installations are fundamentally safer than their predecessors. This improvement is not merely due to better luck; it is the result of architectural shifts.
One of the most revealing aspects of the study is the comparison between indoor and outdoor installations. EPRI’s research indicates that indoor battery facilities were disproportionately represented in historical failure data, often suffering more extensive damage. Conversely, modern outdoor, containerized systems—which allow for better heat dissipation and physical isolation—have demonstrated a significantly lower risk profile.
Furthermore, the data shows that when failures do occur, they are increasingly manageable. Across the 150 incidents studied, 93% resulted in no reported injuries or fatalities. In fact, since the 2019 Surprise, Arizona incident, there have been no injuries or fatalities from BESS failures in the United States. EPRI notes that the failure frequency of BESS is now comparable to that of large, oil-filled transformers—a standard, accepted piece of equipment on the modern electric grid.
The Role of Industry Collaboration
The improvement in safety metrics is a testament to the collaborative nature of the power sector. Utilities, Original Equipment Manufacturers (OEMs), and Engineering, Procurement, and Construction (EPC) firms have invested billions into research and development to address the root causes of thermal runaway.
Events like the upcoming POWERGEN 2027 in Salt Lake City serve as critical forums for this knowledge transfer. By bringing together the stakeholders responsible for designing, building, and operating these systems, the industry fosters a collective intelligence that standardizes safety. Whether it is discussing long-duration storage technologies or refining hybrid system integration, these platforms ensure that the "lessons learned" in one corner of the world are applied globally.
Implications for the Future: Challenges Ahead
While the trajectory is undeniably positive, the industry is not yet at the finish line. EPRI’s report highlights several lingering challenges that must be addressed to maintain this momentum.
The Transparency Gap
Nearly 25% of the incidents in the study were not publicly reported. The absence of a mandatory, federal reporting requirement for BESS failures in the United States and Europe means that the current dataset—while comprehensive—is likely incomplete. Standardizing data reporting would allow the industry to identify trends faster and implement safety upgrades more efficiently.
The Legacy Infrastructure Problem
A significant portion of the current fleet consists of "first-generation" systems that were installed before the current, stringent standards were fully adopted. EPRI strongly recommends that operators of these older systems perform comprehensive safety reviews and, where necessary, undertake retrofits to bring them into compliance with modern standards.
Chemistry and Complexity
The report stops short of naming one lithium-ion chemistry as inherently safer than others at the system level. Because safety is a product of manufacturing, integration, and operational practices, the focus remains on the system rather than the chemistry. As developers look toward even larger, more energy-dense arrays to support grid-scale reliability, the focus must shift to ensuring that, even in the event of a failure, the consequences remain strictly contained.
Conclusion
The evolution of battery storage safety is a triumph of engineering and regulatory foresight. By moving from a period of high-risk experimentation to one of rigorous, standardized safety, the energy sector has cleared a major hurdle on the path to a carbon-free grid.
However, as the industry moves forward, the mission remains clear: continuous vigilance. The goal is no longer just to build batteries that work, but to ensure that the infrastructure supporting our energy future is as resilient and reliable as the communities it serves. With the right combination of data-driven design, mandatory reporting, and industry-wide collaboration, the next decade of battery storage promises not just more power, but safer power.
