The paper highlights the unprecedented transformation of the power sector driven by the increasing share and importance of renewable energy in the contemporary energy landscape. The paper explores the key factors behind the disruption of the power industry which has been taking place for more than a decade and the growing needs of the electricity systems for flexibility. It sets the context of the power sector transformation in Bulgaria looking into the changing energy mix and market environment. It further explores the market fundamentals, which point to a new approach in balancing demand and supply in the electricity system with providers of low carbon flexibility technology. Then, it focuses on the impact of the high share of renewables on electricity prices and the market price signals for investing into electricity storage facilities in Bulgaria in the context of continuous deployment of renewable energy sources (RES) and retiring lignite-fired power plants. In the end it acknowledges that energy storage will play a key role for ensuring stability and reliability in the decarbonized power system, for which the appropriate regulatory framework with de-risking tools need to be put in place to guarantee the sustainable and viable operation of the storage systems.