Transition from monopoly to competition-based markets is widely recognized processes around the globe when it comes to achieving efficient electricity and gas trade thus presenting direct benefits to the final energy consumers. But when talking about smaller infrastructures like district heating (DH) market is still viewed as a natural monopoly. This article presents Lithuanian case to open up existing municipal infrastructure to third-party access in order to complete fuel switch in DH generation faster and to increase efficiency of the entire system through competitive pressure. The article presents the set of circumstances in DH sector back in 2010; focuses on regulatory framework, which was developed and introduced through two phases in Lithuania; and formulates impacts of the reorganization of DH sector from vertically integrated monopoly to single buyer model for de-monopolized generation.