There has been another twist in the long-running saga of Wärtsilä’s energy storage business and how the company aims to run it going forward.
The company intends to run its battery energy storage system (BESS) integration and optimisation division through a joint venture (JV) with German solar PV equipment manufacturer RCT Solutions, the Nasdaq Helsinki-listed marine propulsion and engine power plant company announced to the stock exchange this morning.
Wärtsilä will cease to report the energy storage businesses’ numbers as a separate reporting segment in its financial results, something which was planned for Q2 2026 before this deal was announced.
Its financial targets will no longer apply, and guidance on demand will be suspended.
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The JV transaction, which the company expects to close in the third quarter of this year, will have no material impact on profit and losses at closing, Wärtsilä said.
The transaction could also mark a new chapter for the energy storage business, the fate of which seemed to hang in the balance throughout an 18-month strategic review initiated by Wärtsilä’s leadership in October 2023 and concluded last May.
While all options had been on the table, including divestment, the company had chosen to hold onto a business it entered with the acquisition of US BESS integrator and energy management system (EMS) software specialist Greensmith Energy in 2017.
At the conclusion of the review, Wärtsilä had begun reporting the segment’s financial results separately for the first time and said it was committed to the future success of Wärtsilä Energy Storage and Optimisation (Wärtsilä ES&O) as it was now known.
However, ES&O head Andy Tang, a Greensmith alumnus, left the company shortly thereafter. Tamara De Gruyter, a 30-year employee of Wartsila, was appointed its president and was interviewed by ESN Premium in April.
De Gruyter said Wärtsilä had to “look at what is best for shareholders,” and chose the path it did as “the best way forward for them,” in that interview.
That theme continues with the new steps being taken. Wärtsilä said that while the energy storage division was profitable in 2025, it remained the company’s smallest reported segment by some distance.
Energy storage net sales were just over a tenth of overall net sales, at €694 million (US$805.84 million) in 2025, versus €6.9 billion, and its ES&O order book value last year was €719 million, 8.7% of the €8.25 billion the company booked.
Meanwhile, profitability was 3.3% for energy storage and 12.1% for its other businesses, including gas engine power plants.
Loss expected in 2026, upturn in fortunes expected by end of 2027
Wartsila and its partner, RCT Solutions, will hold a 50% stake each in the JV, while the Finnish tech company will transfer less than 5% of its net assets into the new business.
Solar manufacturing equipment specialist RCT Solutions is already involved in setting up a BESS manufacturing business in the US, a key market for global players.
“After closing the transaction of the joint venture, Wärtsilä will be partnering with an experienced player with strong capabilities in operating an integrated energy storage business in challenging market conditions. RCT Solutions has the aim to develop into a global vertically integrated battery energy storage system player,” Wartsila CEO and president Håkan Agnevall said
Agnevall described the JV as “an excellent opportunity for the Wärtsilä Energy Storage business to strengthen its competitiveness.”
“By combining Wärtsilä’s proven technology, customer base and project expertise with RCT Solutions’ engineering capabilities, vertical integration know-how, and existing manufacturing initiative in the USA, we are creating a foundation to succeed in the rapidly evolving energy storage market,” RCT Solutions CEO Peter Fath said.
Fath will take over as CEO of the JV upon the transaction’s closing. While Wärtsilä said it expects the JV to be loss-making in the short term and represent a €40 million to €50 million hit to its 2026 full-year operating result.
It is, however, expected to generate positive results towards the end of next year, according to the company.
