EticaAG vs. ESS Tech Inc.:
Which Battery Storage Solution is Better for You?
Choosing the right battery energy storage system is no longer just about price or availability. It is about matching technology to real-world needs, whether that means running a hospital during a blackout, balancing wind and solar on the grid, or powering an industrial site without disruption.
Lithium-ion systems and iron flow batteries are built on very different foundations. Lithium-ion has proven itself in short and medium duration storage, but it comes with safety and degradation challenges that need to be addressed. Iron flow batteries promise long duration and non-flammable chemistry, but they trade off efficiency and energy density.
In this comparison, we will look closely at two companies that represent these different paths. EticaAG focuses on immersion-cooled lithium-ion designed for safety-critical environments. ESS Tech builds iron flow systems meant for utility-scale, long-duration projects. By laying out the strengths and limitations of each, we can help asset owners and developers understand which solution is better aligned to their needs.
Table of Contents
Company Overview
EticaAG
- Joint Venture established in 2024. ESS manufacturing since 2019
- Headquartered in Pittsburgh, PA, USA
- Manufacturing in Taiwan and USA (starting 2026)
- Focused on C&I, Microgrid, BTM & Critical Infrastructure Applications
- Differentiated by immersion cooling and hazardous gas neutralization to prevent fire propagation and protect against toxic gas release in lithium-ion systems
ESS Tech Inc.
- Founded in 2011 and publicly listed in 2021
- Headquartered in Wilsonville, OR, USA
- Manufacturing in Wilsonville, OR, USA
- Focused on Utility-Scale, Long-Duration Storage, Renewable Integration, and Grid Services
- Differentiated by iron flow battery chemistry using earth-abundant materials, offering 6-12 hour discharge duration, non-flammable electrolytes, and minimal degradation over time
Chemistry Comparison: Lithium-Ion vs. Iron Flow
Choosing between lithium-ion and iron flow comes down to understanding how each chemistry works, where it excels, and where it struggles. Both approaches can play a role in the clean energy transition, but they are built for different purposes.
Lithium-Ion (EticaAG)
Lithium iron phosphate (LFP) is one of the most widely used battery chemistries in energy storage. It is valued for its high energy density, fast response times, and proven track record in commercial and grid applications. However, traditional lithium-ion systems are prone to thermal runaway and capacity fade over time. EticaAG addresses these weaknesses through immersion cooling and HazGuard gas mitigation technologies, enabling lithium-ion to operate safely and consistently even in compliance-heavy environments.
Key Traits of Lithium-Ion with Immersion Cooling
- High energy density, enabling compact systems for space-limited sites
- Fast response times, ideal for frequency regulation and backup power
- Typically 90-95% round-trip efficiency
- Prone to degradation and safety risks in conventional form, mitigated by immersion cooling and gas neutralization
Iron Flow (ESS Tech Inc).
Iron flow batteries use iron, salt, and water in a circulating electrolyte. Instead of storing energy in solid cells, the system stores it in liquid form, which eliminates risks of fire or thermal runaway. Flow chemistry also allows unlimited cycling with virtually no capacity fade, making it attractive for very long-duration storage. The trade-off is lower efficiency, larger footprint, and slower ramp-up compared to lithium-ion.
Key Traits of Iron Flow
- Extremely safe chemistry with no thermal runaway risk
- Unlimited cycling with 25+ year design life and no capacity fade
- Operates will in long-duration applications (8-22 hours)
- Round-trip efficiency typically 60-70%
- Low energy density, requiring more land and infrastructure per MWh
Putting It Together
Lithium-ion offers efficiency, compactness, and flexibility, but requires advanced engineering to overcome safety and degradation risks. Iron flow offers unmatched safety and longevity, but at the cost of footprint and efficiency. The better choice depends on whether a project prioritizes space and responsiveness or long duration and cycling longevity.
| Category | Lithium-Ion (EticaAG, with Immersion Cooling) | Iron Flow (ESS Tech Inc.) |
|---|---|---|
|
Chemistry |
Lithium-Ion Phosphate (LFP) Cells |
Iron, Salt, and Water Electrolyte |
|
Safety |
Risk of thermal runaway in conventional systems, mitigated by immersion cooling and HazGuard gas mitigation |
Inherently non-flammable, no thermal runaway risk |
|
Energy Density |
High, compact footprint suitable for rooftops, indoors, and space-constrained sites |
Low, requires large tanks and more land per MWh |
|
Round-Trip Efficiency |
90-95% |
60-70% |
|
Cycle Life |
6,000-10,000+ cycles; immersion extends lifetime by stabilizing cells |
Unlimited cycling, no capacity fade over 25 years |
|
Best Duration Fit |
Short to medium (0-8h) |
Long (8-22h) |
|
Response Time |
Milliseconds, ideal for frequency regulation and backup |
Seconds, slower ramp-up but stable for long discharge |
|
Maintenance |
Simple, modular servicing; low complexity |
Pumps and valves add maintenance needs over time |
|
Siting Flexibility |
Compact, modular, deployable indoors or in urban settings |
large footprint, best suited for outdoor utility-scale sites |
Ideal Applications
Different energy storage chemistries excel in different contexts. Duration is one of the clearest dividing lines, but so are safety, siting, and operational requirements. By looking at typical applications, we can see where each company’s technology fits best.
Where EticaAG Fits Best
EticaAG’s immersion-cooled lithium-ion systems are strongest in short to medium duration projects, typically ranging from 0 to 8 hours. These systems deliver high energy density, fast response times, and engineered safety that meets the strictest codes. That combination makes them suitable for environments where downtime or fire risk cannot be tolerated.
Examples Include:
- Commercial and Industrial microgrids needing resilient backup during outages
- Urban deployments on rooftops or in buildings where space is limited
- Critical infrastructure such as hospitals, data centers, and transit systems where toxic gas prevention is essential
- EV fleet depots where rapid cycling and high-power outputs are required
Where ESS Tech Fits Best
ESS Tech’s iron flow batteries are designed for long-duration applications, typically between 8 and 22 hours. Their value lies in unlimited cycling and non-flammable chemistry, which make them well-suited to large projects with ample land and long discharge requirements.
Examples Include:
- Utility-scale renewable integration, storing excess wind and solar for evening or overnight delivery
- Green baseload projects that need 24/7 coverage from intermittent resources
- Remote or rural grids where space is available and long discharge is more valuable than footprint efficiency
Why This Matters:
Lithium-ion, engineered with immersion safety, is the right fit when projects demand compact, responsive systems that can be sited in compliance-heavy or space-constrained areas. Iron flow becomes more attractive when the project priority is multi-hour renewable shifting and safe but land-intensive deployments.
Safety Comparison
Safety is one of the most important considerations in energy storage. Both EticaAG and ESS Tech have built their systems with safety in mind, but they approach the challenge in very different ways.
EticaAG: Engineered Safety
EticaAG begins with lithium-ion, a chemistry that has well-known risks like thermal runaway and toxic gas release. Instead of ignoring these risks, EticaAG directly addresses them through LiquidShield immersion cooling and the HazGuard gas mitigation system. Every cell is submerged in a non-flammable dielectric fluid, which prevents ignition and stops thermal propagation at the source. HazGuard adds another layer of protection by neutralizing hazardous gases such as hydrogen fluoride before they can accumulate.
Because of these active safety systems, EticaAG solutions are well-suited for urban and mission-critical deployments where regulatory and insurance standards are strict. The uniform thermal profile maintained by immersion cooling also extends battery life, ensuring performance in compliance-heavy environments such as hospitals, tunnels, and data centers.
EticaAG - Key Points
-
Cells fully submerged in dielectric fluid to eliminate ignition risk
-
HazGuard neutralizes toxic and flammable gases in real time
-
Uniform cooling extends cell life and prevents thermal hotspots
-
Suitable for enclosed, compliance-heavy environments (hospitals, tunnels, data centers)
ESS Tech: Inherent Safety
ESS Tech’s iron flow batteries use a water-based electrolyte made from iron, salt, and water. This chemistry is inherently non-flammable, which eliminates the risk of thermal runaway without needing additional fire suppression. Because the system does not produce combustible gases during normal operation, there is little need for gas mitigation or complex safety infrastructure.
The trade-off is that ESS systems do not provide active containment at the cell or module level. While the chemistry itself is safe, there is less built-in protection against rare events like mechanical damage or seal failures. As a result, ESS systems are best suited for outdoor, utility-scale projects where space and ventilation are readily available.
ESS Tech - Key Pooints
-
Inherently safe iron-salt-water electrolyte with no fire risk
-
No combustible gases produced under normal operation
-
Lower reliance on additional safety infrastructure
-
Best suited for outdoor, utility-scale projects with space and ventilation
Products Overview
EticaAG
Legion C20
Large-format energy storage for extended C&I use cases where higher power output and scalability are required.
Power Cabinet 340
Modular C&I solutions, delivering high-capacity storage with engineered safety and compact siting.
Power Cabinet 250
Compact modular solution for commercial and industrial applications, combining high energy density with immersion safety.
| Category | Legion C20 | Power Cabinet 340 | Power Cabinet 250 |
|---|---|---|---|
|
Capacity & Output |
3.06 MWh/1.53 MW 2-hour Duration |
340 kWh/160kW 2-hour Duration |
250 kWh/125 kW 2-hour Duration |
|
Duration Range |
2-4 Hours |
2-4 Hours |
2-4 Hours |
|
Footprint |
96″W × 242″D × 102″H |
78″W × 59″D × 97″H |
63″W × 53″D × 98″H |
|
Use Case |
Large C&I, Utility Scale, and distributed energy networks |
Commercial and Industrial |
Commercial and Industrial |
ESS Tech
Energy Warehouse®
Containerized iron flow system for C&I customers, designed for multi-hour duration with no capacity fade.
Energy Center™
Utility-scale platform offering modular multi-hour storage for grid services and renewable shifting.
Energy Base™
Flagship GW-scale platform for long-duration, large-acreage deployments.
| Category | Energy Warehouse | Energy Center | Energy Base |
|---|---|---|---|
|
Capacity & Output |
75 kW/up to 500 kWh per unit |
125 kW/1,000 kWh blocks, scalable to multi-MW |
800 kW/Iron Core block, up to 300 MWh/acre |
|
Duration Range |
5-6 Hours |
~8 Hours |
8-22 Hours |
|
Footprint |
40ft Container |
Configurable Modular Layout |
Land-intensive, Utility-scale Layouts |
|
Use Case |
C&I, Microgrids, and Behind-the-meter |
Utility-scale renewable integration, DER management |
Baseload renewables, grid resilience, multi-day projects |
Check out our full product lineup
Key Differences to Consider
| Key Differences | EticaAG (Immersion Cooled Lithium-Ion) | ESS Tech Inc. (Iron Flow) |
|---|---|---|
|
Duration Fit |
Optimized for short to medium durations (2–4h) |
Designed for long-duration storage (8–22h) |
|
Safety Approach |
Active safety: immersion cooling prevents thermal runaway, HazGuard neutralizes toxic gases |
Inherent safety: non-flammable, water-based chemistry with no fire risk |
|
Energy Density & Siting |
Compact and modular, suitable for rooftops, indoors, and urban deployments |
Large footprint, requires outdoor siting and ample land per MWh |
|
Lifecycle Economics |
High efficiency (90–95%) and uniform thermal control extend battery life and keep financial models accurate |
Unlimited cycling, no capacity fade, but lower efficiency (60–70%) |
|
Response & Power Density |
Millisecond response with high power density, ideal for frequency regulation and backup |
Slower ramp-up and lower power density, suited to steady multi-hour discharge |
The Better BESS For You Is...
There is no single “best” battery energy storage technology. The right choice depends on what the project demands: how long energy needs to be stored, where the system will be located, and how safety is managed.
EticaAG is the better fit for developers and asset owners who need compact systems that deliver strong economics over short to medium durations. Its immersion cooling and HazGuard gas mitigation technologies provide unmatched safety, making it especially well-suited for compliance-heavy, space-constrained, or mission-critical environments.
ESS Tech is the stronger choice for utilities and developers looking for very long-duration storage. Its iron flow chemistry offers unlimited cycling and non-flammable operation, but requires larger land footprints, making it most effective in outdoor, utility-scale projects designed to deliver baseload power from renewables.
In the end, the better BESS depends on your priorities. If safety and siting flexibility are essential, EticaAG delivers. If duration and cycling longevity matter most, ESS Tech has the advantage.
Safe. Resilient. Reliable.
Choose the Safer Path to Energy Storage
See how EticaAG’s fire- and gas-safe BESS solutions compare for your specific site and project requirements.