The analytical brief discusses the importance of demand-side flexibility for power sector transformation. It acknowledges the input and review of experts from various organizations, including Imperial College London, ERCOT, ETSAP, ENTSO-E, Flexitricity, IRENA, and others. The study was supervised by Dolf Gielen and was made available online at www.irena.org/publications. For questions or feedback, readers can contact publications@irena.org.