Z3 Zinc Battery by Eos Energy Enterprises: status and timeline

Z3 Zinc Battery

Z3 is a zinc-based battery system for 3–12 hour grid storage, replacing lithium-ion in utility and microgrid applications. It uses a water-based electrolyte, rates for 100% depth of discharge, and avoids thermal runaway.

ScalingStage 5 of 5

Two production lines operational in 2026; scaling to 8 GWh/year capacity by 2027.

Updated 14 Jul 2026Checked 10 Oct0 updates this week

Milestones

Next · Expand to 8 GWh/year manufacturing capacity

First commercial production line operational2025Complete.
Second production line commissionedQ2 2026Complete.
DOE Loan Guarantee closed3 Dec 2024Complete.
First $68.3M advance received from DOE loan19 Dec 2024Complete.
Expand to 8 GWh/year manufacturing capacityTarget 2027Not yet reached.

Most important updates

Upcoming

2027Expand to 8 GWh/year manufacturing capacity (next)
2027First utility-scale Z3 deployment milestone

Current obstacles

Cost per kWh still above lithium at scaleZinc is cheaper than lithium raw material, but manufacturing cost per kWh is not yet competitive. Eos must hit 8 GWh/year capacity to prove unit economics.
Grid operators' certification inertiaMost grid operators have approved lithium-ion systems. Z3 must undergo extensive testing and operator certification before large deployments.

Physics limits

Discharge duration trade-offZ3's 3–12 hour window is optimal for daily balancing but not for multi-day storage. Grids needing 24+ hour hold use long-duration batteries (iron-air, compressed air) instead.
Zinc re-dissolution and dendriteDespite electrolyte engineering, zinc dendrite can still form and reduce cycle life on faster charge rates or in hot climates. These factors constrain how aggressively Z3 can be cycled.

How it works

3 parts

Zinc cathode

Hybrid cathode chemistry

Zinc hybrid cathode with conductive plastic anode and carbon felt, managed by water-based electrolyte.

Modular system

Scalable modules to MWh systems

Individual Z3 modules (0.8 kWh each, 20.5 kg) are assembled into larger systems at utility scale, from hundreds of kW to tens of MWh, depending on grid needs.

Cooling

Passive and active thermal management

Z3 cells are designed to minimize heat generation. Systems can use passive cooling in most climates, with active cooling only where needed.

Spec sheet

Spec	Z3 Zinc Battery
Discharge duration	3–12 hours^R (reported)
Depth of discharge	100%^R (reported)
Rated cycle life	6,000 cycles (~20 years)^R (reported)
Round-trip efficiency	Up to 79%^R (reported)
Target manufacturing capacity by 2027	8 GWh/year^R (reported)

^R reported by the company

Update log

4 updates

About Eos Energy Enterprises

The team behind Z3 Zinc Battery

Eos Energy Enterprises

Z3 zinc battery, grid storage, 3-12 hours

Eos Energy manufactures zinc-based long-duration energy storage systems for utility grids and industrial sites. The Z3 battery uses a non-lithium water-based chemistry for 20+ year service. Expanding to 8 GWh/year by 2027.

H1 2026 revenue surpassed all of 2025; record backlog ~$807M; two production lines running.
First $68.3M advance received from $303.5M DOE Loan Guarantee; expanding to 8 GWh/year by 2027.
Z3 achieves 100% depth of discharge; 6,000 cycles over ~20 years; up to 79% round-trip efficiency.

eose.com (opens eose.com)Company profile →

Founded: 200818 yrs
Headquarters: United States
Status: Public
Listed: EOSE (opens google.com)NASDAQ
Valuation: public
Raised: $304M1 round
Last round: DOE Loan Guarantee · $304M3 Dec 2024
Works in: EnergyGrid storage
Coverage: 1 program · 4 updateslatest 14 Jul 2026checked 10 Oct
Lead investors: US Department of Energy
Partners: US Department of Energy (opens energy.gov)
Investors: Cerberus Capital Management (opens cerberuscapital.com)
People: Joseph R. Mastrangelo Jr. (opens investors.eose.com)CEO & DirectorJoseph Nigro (opens investors.eose.com)Chair of the Board

Spec

Z3 Zinc Battery

Discharge duration

3–12 hours^R (reported)

Depth of discharge

100%^R (reported)

Rated cycle life

6,000 cycles (~20 years)^R (reported)

Round-trip efficiency

Up to 79%^R (reported)

Target manufacturing capacity by 2027

8 GWh/year^R (reported)

Z3 Zinc Battery

Milestones

Most important updates

Upcoming

Current obstacles

Physics limits

How it works

Hybrid cathode chemistry

Scalable modules to MWh systems

Passive and active thermal management

Spec sheet

Update log

Tue 14 Jul

Thu 9 Apr

Thu 19 Dec 2024

Tue 3 Dec 2024

About Eos Energy Enterprises

Current obstacles

Physics limits

How it works

Hybrid cathode chemistry

Scalable modules to MWh systems

Passive and active thermal management

Spec sheet

Update log

Tue 14 Jul

Thu 9 Apr

Thu 19 Dec 2024

Tue 3 Dec 2024

About Eos Energy Enterprises