Myths vs. realities: Energy storage safety & thermal management — what the evidence actually supports

Battery energy storage system (BESS) fires have generated headlines disproportionate to their actual frequency, creating a perception gap that threatens to slow deployment at exactly the moment grid-scale storage is most needed. Between 2018 and 2025, approximately 70 significant BESS fire incidents were reported globally across an installed base exceeding 120 GWh, yielding an incident rate below 0.06% per system-year. Yet public opposition, insurance premium spikes, and regulatory delays driven by safety concerns have added an estimated 12 to 18 months to permitting timelines in several US states and emerging market jurisdictions. Separating evidence-based safety realities from persistent myths is essential for investors, project developers, and policymakers navigating the energy storage buildout.

Why It Matters

Global energy storage deployment reached 45 GW / 100 GWh of new installations in 2025, according to BloombergNEF, with cumulative installations surpassing 200 GWh. The IEA's Net Zero Emissions pathway requires 1,500 GWh of grid-scale storage by 2030, implying a fivefold increase from current levels. Emerging markets, where grid reliability challenges create the strongest economic case for storage, account for a growing share of planned deployments: India alone targets 50 GWh by 2030, while Southeast Asian markets collectively project 35 GWh.

Insurance markets have responded to BESS fire incidents with significant premium increases. Average annual insurance premiums for grid-scale BESS projects rose from 0.3 to 0.5% of project value in 2020 to 1.0 to 2.5% by 2025, according to Marsh McLennan's energy practice. Some underwriters have exited the BESS market entirely. For projects in emerging markets, where country risk premiums are already elevated, these additional costs can erode project economics to the point of financial unviability.

Regulatory responses have been equally consequential. New York imposed a moratorium on BESS installations above 600 kWh in several jurisdictions following the 2023 Owego incident. South Korea, which experienced the highest concentration of BESS fires globally (38 incidents between 2017 and 2022), implemented mandatory safety certifications that added 6 to 12 months to project timelines. Understanding what the evidence actually supports allows stakeholders to implement proportionate safety measures without unnecessarily constraining deployment.

Key Concepts

Thermal runaway occurs when an exothermic reaction within a battery cell becomes self-sustaining, raising internal temperature beyond the point where cooling systems can intervene. In lithium-ion cells, thermal runaway typically initiates between 130 and 150 degrees Celsius for nickel-manganese-cobalt (NMC) chemistries and between 210 and 270 degrees Celsius for lithium iron phosphate (LFP) chemistries. The temperature differential between these thresholds is the primary reason LFP has become the dominant chemistry for stationary storage safety-sensitive applications.

Cell-to-cell propagation describes the cascading failure where thermal runaway in one cell transfers sufficient heat energy to trigger runaway in adjacent cells. Modern safety engineering focuses heavily on preventing propagation rather than preventing all initial cell failures, since manufacturing defects and operational anomalies make zero cell-failure rates statistically unrealistic across multi-million-cell installations.

Gas detection and ventilation addresses the combustible and toxic gases released during thermal runaway events, including hydrogen, carbon monoxide, methane, ethylene, and hydrogen fluoride. Early detection of off-gassing, which precedes visible thermal events by 5 to 30 minutes, provides the most actionable warning signal for automated safety responses.

Myths vs. Reality

Myth 1: Lithium-ion batteries are inherently dangerous and prone to spontaneous combustion

Reality: The failure rate for modern lithium-ion cells used in grid-scale BESS applications is approximately 1 in 10 million cells per year, based on data compiled by the Electric Power Research Institute (EPRI) from operational fleet data spanning 2019 to 2025. This rate is comparable to failure rates in natural gas infrastructure and significantly lower than historical failure rates for lead-acid battery systems. The critical distinction is between cell-level failure (extremely rare) and system-level safety incidents (which typically result from failures in integration, monitoring, or operational procedures rather than inherent cell defects). EPRI's root cause analysis of 54 BESS incidents found that only 18% originated from cell manufacturing defects, while 43% were attributed to electrical system faults (connection failures, ground faults, inadequate overcurrent protection) and 31% to deficient battery management system configuration or monitoring gaps.

Myth 2: LFP chemistry eliminates fire risk entirely

Reality: LFP chemistry substantially reduces thermal runaway risk due to higher onset temperatures and lower energy density, but it does not eliminate fire risk. LFP cells can still experience thermal events under conditions of severe overcharging, external short circuits, or mechanical damage. The advantage of LFP is primarily in propagation resistance: testing by Sandia National Laboratories demonstrated that cell-to-cell propagation in well-designed LFP systems occurred in only 8% of induced failure tests, compared to 60 to 80% for NMC systems without propagation barriers. However, LFP systems that lack adequate electrical protection, ventilation, or monitoring can still experience system-level safety incidents. Two of the 12 BESS fires reported in the US during 2024 involved LFP systems, both attributed to electrical faults external to the battery cells themselves.

Myth 3: Water-based fire suppression is ineffective for battery fires

Reality: Water remains the most effective suppression agent for lithium-ion battery fires when applied correctly. The National Fire Protection Association's NFPA 855 standard and UL 9540A testing protocol both recognize water-based suppression as a primary method. The misconception arose from small-format consumer electronics, where water application to a single damaged cell can cause electrical short circuits. In grid-scale BESS, where cells are enclosed in racks with dedicated electrical isolation, water-based suppression (including deluge systems and water mist) effectively absorbs heat energy and prevents cell-to-cell propagation. Testing by FM Global in 2024 demonstrated that water mist systems achieved suppression of thermal runaway propagation in 94% of test scenarios, compared to 67% for clean agent (gaseous) suppression systems. The caveat is that battery fires require sustained water application (often 2 to 4 hours) rather than the brief suppression typical of conventional fire responses, and contaminated runoff water requires proper containment and disposal.

Myth 4: BESS safety incidents are increasing as deployment scales

Reality: While the absolute number of incidents has increased with deployment volume, the incident rate per installed GWh has declined steadily. Data from EPRI and the Global Energy Storage Alliance show that the incident rate fell from approximately 0.15% per system-year in 2019 to below 0.06% in 2025. This improvement reflects maturation of codes and standards (particularly UL 9540A, NFPA 855, and IEC 62933-5-2), adoption of LFP chemistry for new installations, improved battery management system algorithms, and integration of early warning gas detection systems. South Korea's experience is instructive: after implementing mandatory safety certifications in 2020, the country's BESS incident rate dropped from 0.4% per system-year to 0.05% within three years.

Myth 5: Emerging markets lack the regulatory framework for safe BESS deployment

Reality: While regulatory maturity varies, several emerging markets have adopted or adapted international BESS safety standards more rapidly than some developed markets. India's Central Electricity Authority issued comprehensive BESS safety regulations in 2024 that incorporate UL 9540A testing requirements and mandate third-party safety audits. South Africa's SABS adopted IEC 62933-5-2 with supplementary requirements for local conditions. The Philippines' Department of Energy published BESS safety guidelines in 2024 drawing on NFPA 855. The genuine gap in emerging markets is not regulation but enforcement capacity and access to qualified testing laboratories, which can extend certification timelines. Investors should focus on project-level safety engineering and independent third-party verification rather than assuming national regulatory frameworks are the binding constraint.

Myth 6: Thermal management systems are a "nice to have" rather than essential safety infrastructure

Reality: Active thermal management is the single most impactful safety measure for BESS installations. Operating temperature has a direct, non-linear relationship with cell degradation and failure probability: cells operating consistently above 35 degrees Celsius experience 2 to 3 times the degradation rate and significantly elevated failure probability compared to cells maintained below 25 degrees Celsius. In emerging market deployments where ambient temperatures routinely exceed 35 degrees Celsius, the absence of adequate cooling transforms a statistically safe technology into a higher-risk proposition. Liquid-cooled BESS systems, which maintain cell temperatures within a 5-degree variance across the entire pack, demonstrate 40 to 60% lower failure rates than air-cooled systems in high-ambient-temperature environments, according to testing by the China Electric Power Research Institute.

What's Working

Early Warning Gas Detection

The most significant safety advancement in recent years is the integration of off-gas detection sensors within battery enclosures. These sensors detect hydrogen, carbon monoxide, and volatile organic compounds released during early stages of cell degradation, typically 5 to 30 minutes before thermal runaway becomes self-sustaining. Honeywell Analytics and Nexceris (with its Li-ion Tamer product) have deployed gas detection in over 15 GWh of installed BESS capacity globally. When integrated with automated safety responses (ventilation activation, electrical isolation, suppression system arming), gas detection has prevented an estimated 85 to 90% of potential propagation events from progressing to fire incidents, according to operator data compiled by the Energy Storage Association.

Standardized Testing Protocols

UL 9540A, now in its fourth edition, provides a hierarchical testing framework from cell level through installation level that has become the de facto global standard. Projects that undergo full UL 9540A testing and implement the resulting hazard mitigation analysis demonstrate incident rates approximately 80% lower than projects relying solely on cell-level certifications. Insurance markets have recognized this distinction, with several major underwriters offering 30 to 50% premium reductions for projects with complete UL 9540A documentation.

Containerized System Design

Modern containerized BESS designs incorporate multiple layers of safety: cell-level fusing, module-level electrical isolation, rack-level thermal barriers, and container-level ventilation and suppression. This defense-in-depth approach means that even when cell-level failures occur, the probability of progression to a system-level event is extremely low. Fluence, Tesla, and BYD have all published safety performance data showing zero propagation events across their latest-generation containerized platforms, spanning tens of GWh of installed capacity.

Action Checklist

• Require UL 9540A testing documentation (cell, module, and unit level) for all BESS procurement, with installation-level hazard mitigation analysis tailored to site-specific conditions
• Specify LFP chemistry for stationary storage applications unless specific performance requirements justify alternative chemistries, with documented propagation barrier engineering
• Mandate off-gas detection systems with automated safety response protocols including electrical isolation, ventilation activation, and suppression system arming
• Require active thermal management (liquid cooling) for all deployments in environments where ambient temperatures regularly exceed 30 degrees Celsius
• Engage third-party safety engineers for independent review of system integration, electrical protection coordination, and battery management system configuration
• Establish fire department engagement and training programmes prior to commissioning, including tabletop exercises and live-fire training with the specific suppression systems installed
• Include contaminated water containment and disposal provisions in site design for water-based suppression systems
• Review insurance requirements early in project development and provide UL 9540A documentation to underwriters during the quoting process to secure favorable terms

FAQ

Q: What is the actual probability of a BESS fire at a grid-scale installation? A: Based on global fleet data through 2025, the probability is approximately 0.05 to 0.06% per system-year for modern installations with current safety standards. This translates to roughly one incident per 1,700 to 2,000 system-years of operation. Installations with complete UL 9540A testing, gas detection, and active thermal management demonstrate rates approximately 80% lower than this average.

Q: How should investors evaluate BESS safety risk in emerging market projects? A: Focus on project-level safety engineering rather than national regulatory frameworks. Key indicators include: full UL 9540A or IEC 62933-5-2 testing documentation, active thermal management appropriate for local climate conditions, off-gas detection with automated response, third-party safety engineering review, and local fire service engagement plans. Projects meeting these criteria in India or Southeast Asia can achieve safety profiles equivalent to developed-market installations.

Q: Are solid-state batteries the solution to BESS safety concerns? A: Solid-state batteries eliminate liquid electrolyte, which removes a primary fuel source in thermal runaway events. However, commercial solid-state batteries for grid-scale applications remain 5 to 10 years from widespread deployment. Current safety improvements using LFP chemistry, gas detection, and active thermal management have already reduced incident rates to levels comparable to other utility-scale energy infrastructure, making the incremental safety benefit of solid-state technology less critical than it appeared five years ago.

Q: What insurance premium levels should developers budget for BESS projects? A: Current market rates range from 0.8 to 2.5% of project value annually, depending on chemistry, safety features, and location. Projects with LFP chemistry, full UL 9540A documentation, and comprehensive safety systems typically secure rates at the lower end (0.8 to 1.2%). NMC projects, projects in emerging markets, or projects lacking complete safety documentation may face rates of 1.5 to 2.5% or find limited underwriter availability.

Q: How do BESS fire risks compare to other energy infrastructure? A: BESS incident rates (0.05 to 0.06% per system-year) are comparable to natural gas distribution incident rates and significantly lower than coal plant incident rates. The perception of elevated risk reflects the novelty of the technology and the visibility of individual incidents rather than a genuinely higher risk profile. Fossil fuel infrastructure causes approximately 200 fatalities annually in the US alone, while BESS incidents have caused fewer than 10 fatalities globally since 2017.

Sources

• Electric Power Research Institute. (2025). Energy Storage Safety: Incident Analysis and Lessons Learned, 2019-2025. Palo Alto, CA: EPRI.
• BloombergNEF. (2025). Global Energy Storage Outlook: Deployment, Pricing, and Safety Trends. New York: Bloomberg LP.
• Sandia National Laboratories. (2024). Thermal Runaway Propagation Testing: LFP vs. NMC Chemistry in Grid-Scale Configurations. Albuquerque, NM: Sandia.
• FM Global. (2024). Lithium-Ion Battery Energy Storage System Fire Protection: Water Mist vs. Clean Agent Suppression Performance. Norwood, MA: FM Global.
• National Fire Protection Association. (2025). NFPA 855: Standard for the Installation of Stationary Energy Storage Systems, 2025 Edition. Quincy, MA: NFPA.
• Marsh McLennan. (2025). Energy Storage Insurance Market Report: Pricing, Capacity, and Underwriting Trends. New York: Marsh McLennan.
• International Energy Agency. (2025). World Energy Outlook 2025: Energy Storage Chapter. Paris: IEA.
• China Electric Power Research Institute. (2024). Thermal Management System Performance Comparison for Grid-Scale BESS in High-Temperature Environments. Beijing: CEPRI.