Battery Firm ESS to be Publicly Listed; Value Expected to Cross $1 Bn

Battery Firm ESS to be Publicly Listed; Value Expected to Cross $1 Bn

ESS Tech, a manufacturer of iron flow batteries has entered into an agreement that will result in it becoming a publicly listed company.

ESS Tech, a manufacturer of long-duration iron flow batteries for commercial and utility-scale energy storage applications, and ACON S2 Acquisition, a publicly traded special purpose acquisition company, have announced they have entered into a definitive agreement for a business combination that will result in ESS becoming a publicly listed company.

Founded in 2011 with a mission to develop the cleanest, lowest-cost long-duration energy storage systems on the market, ESS developed an iron flow battery technology with innovative technological breakthroughs that is built to transform the utility grid by enabling safe, environmentally-friendly, long-duration storage. Unlike traditional lithium-ion batteries that are made from hazardous and costly materials, ESS’ patent-protected battery solutions use abundant iron, salt and water, making them environmentally safe and cost-effective energy storage systems.

The business combination values the combined company at a USD 1.072 billion pro forma enterprise value. The transaction will provide approximately USD 465 million of pro forma net cash to the combined company, assuming no redemptions by ACON S2 shareholders. As part of the transaction, ACON S2 raised a USD 250 million fully committed PIPE from institutional investors including Fidelity Management & Research Company LLC, SB Energy Global Holdings Ltd, a wholly-owned subsidiary of SoftBank Group Corp., Breakthrough Energy Ventures and BASF Venture Capital.

“The goal of ESS from its inception has been to develop a fundamentally new, high-performance battery technology,” said ESS CEO Eric Dresselhuys. “Our team has delivered on that goal over the last decade by developing patent-protected iron flow battery technology that is well-suited for the grid and the environment. Unlike currently available approaches, our solution offers a green, lower lifecycle cost, energy storage system with performance that doesn’t degrade over time. We’re excited about today’s announcement as it marks the beginning of our next chapter to capitalize on burgeoning opportunities in the long-duration energy storage market.”

Renewable energy deployment is increasing dramatically, with installation records set each year and now surpassing other forms of new generation coming online. In the long run, grid-scale energy storage will need the capabilities of long-duration storage to pick up the load for four to twelve hours when variable generation wanes, yet be flexible enough to support fast-changing grid needs. The total addressable market for energy storage systems is expected to grow at a 34 percent CAGR from USD 8 billion in 2020 to USD 56 billion in 2027, driven primarily by growing deployments of solar and wind power, as well as a desire to increase the power grid’s resiliency. ESS’ energy storage systems provide an optimal solution for utilities, independent power producers and microgrids seeking a reliable, safe and durable solution for four- to twelve-hour power storage that doesn’t degrade over time. That is the capability that ESS iron flow battery technology can deliver.

Craig Evans, ESS President and Co-founder stated, “Our team worked diligently for the last decade to create a storage solution that could provide a meaningful addition to the world’s transition to a renewable future. We have made incredible strides to that end and I am very excited about the next phase for ESS and our ability to accelerate our growth.”

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Ayush Verma

Ayush is a staff writer at and writes on renewable energy with a special focus on solar and wind. Prior to this, as an engineering graduate trying to find his niche in the energy journalism segment, he worked as a correspondent for