ESS Tech, Inc. has been added to the Russell Microcap Index, effective upon the U.S. market opening on June 29, as part of the first 2026 Russell indexes reconstitution. This inclusion expands the company's visibility among institutional investors and validates its strategic focus on non-lithium energy storage solutions. The company is accelerating development of its U.S.-made sodium-ion battery platform to meet demand from AI infrastructure and data centers, with early-stage opportunities approaching $1 billion.

Drew Buckley, CEO of ESS, stated that the addition comes at a pivotal moment as the company advances its iron flow technology for long-duration applications. The Russell indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for active investment strategies. Approximately $12.2 trillion in assets are benchmarked against the Russell U.S. Indexes as of the end of June 2025.

The June reconstitution captures up to the 4,000 largest U.S. stocks as of April 30, ranked by total market capitalization. Membership in the Russell 3000 Index is re-evaluated twice per year and includes automatic additions to the large-cap Russell 1000 Index or small-cap Russell 2000 Index. FTSE Russell determines membership primarily by objective, market-capitalization rankings and style attributes.

ESS Tech, Inc. is a provider of non-lithium energy storage solutions established in 2011. The company focuses on accelerating decarbonization through longer-lasting energy storage using easy-to-source materials. Its solutions aim to enable energy security, reliability, and resilience for customers facing increasing energy demand.

Key Details

The company continues to advance its iron flow technology while pursuing opportunities in high-growth markets. Inclusion in the Russell Microcap Index is expected to enhance ESS's profile with institutional investors as it seeks to deliver long-term value for shareholders.

ESS Tech, Inc. has generated early-stage opportunities approaching $1 billion for its planned U.S.-made sodium-ion battery energy storage system (BESS) offering. The demand spans data centers, critical infrastructure, and utility markets, exceeding expectations with limited outbound marketing. This surge in interest follows the company's announcement of a letter of intent with Alsym Energy seven weeks ago.

The company is accelerating the development of its sodium-ion BESS platform to address growing near-term demand. The systems are designed for short- and medium-duration applications, a segment historically served by lithium-ion systems. ESS Tech is aligning its resources to support an expanded focus on AI infrastructure and data center markets.

Market Opportunities

The early customer engagement highlights a shift toward safer, domestically sourced energy storage solutions. The opportunities identified by ESS Tech are concentrated in sectors requiring reliable and secure power backup.

ESS Tech, Inc. (NYSE: GWH) positions itself as a leading provider of non-lithium energy storage solutions. The company's strategic pivot aims to capitalize on the specific needs of AI data centers and other critical infrastructure sectors.