1977 – Beginning the transformation of Kardoskút depleted gas field into an underground storage site. The process continued in Pusztaederics and Hajdúszoboszló, by putting in operation these assets as well. The latest – in the 80ies - built storge site is Zsana. The operation of the underground storage sites was managed by MOL Földgáztároló Rt.

April 1, 2006 – After 16 months of approval procedure of the Hungarian and European authorities, E.ON Ruhrgas International AG (ERI) takes over 100% of the shares in MOL Földgázellátó Zrt and MOL Földgáztároló Zrt. The former natural gas storage company of Hungary has a new name and a new brand: E.ON Földgáz Storage Zrt.

2007 – Beginning the development of Zsana underground storage site.

November 2009 – Finishing the development of Zsana underground storage site, and through that the largest and most flexible underground storage site in Central-Eastern-Europe was putted in operation.