One of Finland's largest energy storage facilities commissioned in Lappeenranta – Merus Power's EUR 15 million delivery completed

The energy storage facility delivered by Merus Power to Lappeenranta, Finland, has been completed and put into market use on 15 May 2025. The energy storage facility is owned by a joint venture between Ardian’s Clean Energy Evergreen Fund and the local energy provider Lappeenrannan Energia. It is the largest energy storage facility in use on the Finnish electricity market with an output of approximately 38 megawatts and energy of 43 megawatt hours. The completion of the project is significant for Merus Power, as it is the largest energy storage facility manufactured by the company. 

“Merus Power operates as an EPC operator, offering its customers comprehensive solutions on a turnkey basis. In this project, the delivery included an energy storage system with installation and commissioning, as well as the management of network requirements. We manage the entire value chain from development to construction, from testing to market. In addition to technical know-how, energy storage facilities require also an understanding of the market and regulation – and this is where our strengths come at play. We have manufactured and put into market use numerous electricity storage facilities," says Kari Tuomala, CEO of Merus Power. 

Power like in a small power plant 

The output of 38 megawatts corresponds to the production capacity of a small power plant, and the nominal capacity of 43 megawatt hours would be enough to cover the electricity consumption of more than 35,000 households, i.e. households about the size of Lappeenranta, for two hours. One of the most important features of an energy storage facility is its ability to respond to the needs of the grid in fractions of a second. It is precisely this kind of flexibility that is crucial for maintaining the stability of Finland's power grid. 

The energy storage facility is in the Mertaniemi area of Lappeenranta and operates as part of the regional energy structure. The investment project was developed by Ardian Clean Energy Evergreen Fund’s Finnish investment platform eNordic in cooperation with Lappeenrannan Energia. 

Benjamin Kennedy, Managing Director Infrastructure - Renewables, Ardian, said: ”The completion of Mertaniemi is a major milestone for us, representing the Ardian Clean Energy Fund’s first investment in battery energy storage in Finland. As the country’s wind power capacity continues to grow, the demand for storage solutions has only increased, making this asset critical to maintaining the stability of the grid and providing greater reliability. We are proud to have brought this solution online within 18 months, and we see significant opportunity to invest in battery storage in the Nordics, where we plan to continue building out our platform.”

Towards a smarter and cleaner electricity system 

Energy storage facilities are a critical part of the green transition energy system. They provide flexibility in situations where renewable energy production fluctuates and enable electricity to be stored when it is available in abundance and at a low cost. 

”This is the first energy storage investment for Ardian. It is an important step in the implementation of our strategy in Finland and more broadly in the Nordic countries. We see significant investment opportunities in combining  renewable energy generation and battery electricity storage technology to build a more stable and sustainable energy system. Ardian's and eNordic's strong position in the Nordic countries and their experience in the long-term development of renewable energy create excellent conditions to drive the energy transition," says Eero Auranne, CEO, eNordic Oy.