Finland and Estonia’s Estlink connections were interrupted – The reason was the testing of a large battery park

The battery warehouse built in Kiisa, Estonia has started full-scale operation at the beginning of February. This is a historic achievement for the Baltic energy sector.

The large battery park is the first of two projects. Hertz 1 and Hertz 2 are each energy storages with a storage capacity of 200 megawatt hours and a nominal output of one hundred megawatts.

The purpose of the battery parks is to stabilize the electricity system, especially since the Baltics separated from the Russian electricity grid and moved to the European continental grid.

The Hertz 1 battery park, which has now started operating, is located only 25 kilometers southwest of Tallinn. The battery warehouse consists of 54 containers containing a total of 2,328 battery modules.

The construction of the Hertz 2 battery park is already well underway in Aruküla, in the northeastern part of the country. It is supposed to be completed during the current year.

When both battery storages are ready, the combined capacity will rise to 400 megawatt hours and the power to 200 megawatts.

The battery complex will be one of the largest in continental Europe.

The total investment is estimated at 200 million euros.

The background of the Hertz projects is Baltic Storage Platform (BSP). It is a Baltic energy company Evecon’sa French solar company Corsica Solemin and investment company People joint venture.

Problems with testing

The Hertz 1 battery park underwent final grid connection testing on January 20, 2026. It resulted in an outage that temporarily affected the Estonian electricity system.

As a result of the malfunction, both Estlink connections between Finland and Estonia were interrupted, which in turn led to a power loss of about a thousand megawatts in the Estonian network.

One thousand megawatts is about 20 percent of the electricity load in the Baltic region in winter.

The power deficit was initially compensated with the support of the continental European power grid, which was followed by the introduction of reserve capacity in the Baltic countries.

News about the topic, among other things Evening newspaperEstonian Business paper and PV Magazine.