Increasingly, coal-fired power plants are required to balance power grids by compensating for the variable electricity supply from renewable energy sources. For this, high flexibility is needed, in terms of possessing resilience to frequent start-ups, meeting major and rapid load changes, and providing frequency control duties. This report reviews the means available and under development for achieving flexibility. Potential damage mechanisms are well known, and the necessary flexibility can be achieved with acceptable impacts on component life, efficiency and emissions. Designs are being developed to enable flexibility in future plants.