Sunly, Tallinn-based renewable energy developer active across the Baltic states, and Rolls-Royce Power Systems have signed contracts to build four battery energy storage systems (BESS) in Latvia. At a combined 490 MWh, it’s the largest battery storage agreement struck by a privately owned company in the region. The deal was announced at the opening of Sunly’s new solar park in Valmiera, which is set to become one of Latvia’s first hybrid energy parks, pairing solar generation with battery storage on the same site.
The Valmiera battery system goes live in the first quarter of 2027. The remaining three sites follow later that year.
One contractor, four sites — how Sunly and Rolls-Royce plan to collaborate
Sunly handed the whole project to Rolls-Royce rather than splitting it across several suppliers, covering design, equipment, construction and handover.
“Our strength lies in supplying integrated, high-performance battery energy storage systems. As main contractor, we provide a single point of responsibility towards our customers, which helps them reduce risks and complexity, secure bankable performance and maximise long-term asset value,” said Andreas Görtz, President of the Mobile and Sustainable business unit at Rolls-Royce Power Systems.
The systems will run on Rolls-Royce’s mtu EnergyPack platform, which manages the timing of energy storage and release back to the grid.
Why batteries, why now
The deal comes against a broader shift in how the Baltic states operate their power grids. Since disconnecting from the Russian electricity system and synchronising with the European network, Latvia, Lithuania and Estonia have opened their balancing markets to private operators. Battery storage is one of the fastest ways to keep grid frequency steady under that arrangement.
That context shaped who Sunly picked as a partner, according to CEO Priit Lepasepp: “As a provider of vital services, we must meet strict cybersecurity requirements. For us, it was essential to find a European partner who could take full responsibility for the entire project and had already proven their capability in Latvia. Rolls-Royce had delivered for the Latvian grid operator AST in 2025, and the same team will now build all four of our sites.”
Görtz framed it similarly: “Together with Sunly, we are delivering large-scale battery storage systems that will play a critical role in strengthening grid stability and energy security in the Baltics. By providing fast, flexible and reliable capacity, our BESS solutions support the integration of renewable energy, improve system resilience and contribute to a more secure and sustainable energy infrastructure.”
Estonia is next
Latvia is the opening move. Sunly and Rolls-Royce have also signed a memorandum of understanding to extend the partnership to Estonia, with a 300 MWh project earmarked for Risti. Add that to the Latvian sites and the pipeline runs to roughly 790 MWh across the two countries.
Lepasepp ties the deal back to Sunly’s broader bet on pairing solar power with storage, so electricity generated when the sun is out can still be used after dark: “Our aim is to build an energy system that works for people, not just when the sun shines. By combining solar generation and battery storage, we can produce energy when conditions are right and deliver it when it is needed, making renewable energy more reliable and less dependent on weather conditions. Co-locating generation, storage, and consumers like data centres in one place is how renewable energy becomes truly efficient. Latvia is the start. Estonia is next. And we have the right partner to get there.”
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