On 6 February, the largest thermal storage facility in the Baltics was opened. The Estonian heating provider Utilitas commissioned the 1100-MWh-Väo storage — a kind of big thermos – in the Estonian capital of Tallinn.
The Väo site is the first large-scale heat accumulator in Tallinn, with two more to follow, the company writes in a press release. The idea is that with the storage of heat, the use of fossil fuels to heat up homes, offices and other buildings will diminish. The heat is distributed using a district heating system of pipes.
Olympic swimming pools
The Väo thermal storage facility is 42 metres (138 feet) high and 26 metres (85 feet) in diameter. It can store up to 20,000 cubic metres (5,283,441 US gal.) of water — equal to the capacity of almost eight full-size Olympic swimming pools. Swedish construction company Granitor built the 80-megawatt facility, with a total cost of about EUR 8 million. The water is heated by power generated with wood chips and other local leftovers from forestry industry turned into biomass.
Largest heat storage in the world
While the Väo “thermos” is the biggest in the Baltic States, the biggest in the world is being constructed underground in a cavern further north, in Vantaa, Finland. Vantaan Energia there is constructing “Varanto”. It is set to open by 2030 and hold 1.1 million cubic metres (290,589,257.6 US gal.) of water, or a capacity of 90 GWh. | © 2026 Marcel Burger, nordicreporter.com. Press photo of the Väo site by Utilitas. The big “thermos” to the far right of the photo.