Developers say it will bring greater energy security in the wake of decoupling from the Russian BRELL grid last year, and connection to the continental European grid.

Located just 25 kilometers south of Tallinn, the facility, called Hertz 1, is a significant technical upgrade for Estonia and includes a high-voltage 330 kV connection to the main grid, via underground cable.

This development boosts the physical resilience of connectivity and sets a new standard for integrating large storage units into the national grid, "Aktuaalne kaamera" reported.

The facility was built by Estonian firm Evecon and funded by French investors, including Corsica Sole, a French independent solar power producer.

"We did it in France, we did it in Belgium, and now, it's the moment for the Baltics to turn in this wonderful world, decarbonize with more wind, more solar and stabilized energy. Hopefully we think that this investment will be paid off during 10 years," said Corsica Sole CEO Michael Coudyser. The batteries' expiry time is about 10 years, he added. "Of course, it depends how we use it."

"With the projects on the platform operating simultaneously, we could cover the electricity consumption of 90,000 households," Evecon CEO Karl-Joonatan Kvell noted.

"We need to ensure stability in complex conditions where consumption and production can fluctuate significantly. Additionally, since February's [2025] desynchronization [from the Russian power grid], Estonia has been obliged to maintain the region's frequency and grid balance on its own. This is precisely the scale at which a battery park can contribute by providing flexible services and participating in the market," Kvell went on.

Rated at 100 MW, the battery park is based on a container solution – 54 of the containers house a total of 2,328 battery modules, along with battery racks, cooling, fire protection, and monitoring systems, forming a secure and self-contained unit. This modular approach allows the system to efficiently store and release electricity, ensuring reliability throughout its lifecycle, the project's developers say.

Kiisa testing led to Estlink malfunction last month

However, the birth of the Kiisa battery park has not been completely smooth. Late last month, testing ahead of launch caused a malfunction in both Estlink electricity cables linking Estonia and Finland, leading to a 1,000 MW generation shortfall.

"I can confidently confirm that the given test has been successfully completed, approved by Elering, and that the battery park has been reliably designed and built in accordance with applicable requirements," Kvell said on this.

Kiisa's Herz 1 to be joined by sister facility in Aruküla

The facility is also to be joined by a sister project in Aruküla, also near Tallinn, at a cost of €170 million and also built by Evecon together with renewable energy company Corsica Sole and investment fund Mirova. This marks the largest current private investment in Estonia's energy sector.

Minister of Energy and Environment Andres Sutt (Reform) said Estonia will certainly need more battery parks like Kiisa and Aruküla.

"Such parks help cut price spikes or price volatility, which from the consumer's perspective is needed in every way, because I think everyone is interested in a more stable electricity price. And it is equally important from the investor's point of view: the more predictable the electricity price, the easier it is to make investments," he said.

"Elering already has nearly one thousand megawatts of battery storage under contract, so I believe we are all moving in the right direction," Sutt added.

Hertz 1 began operating at full capacity on Tuesday, with construction on Hertz 2 in Aruküla already underway.

When both stations are up and running, at the end of this year, their total capacity will reach 200 MW, and 400 MWh, which will mean one of the most powerful battery complexes in continental Europe being located in Estonia.

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