Due to Horizon 2030 objectives, industry is committed to improving traditional auxiliary bi-drum boilers performance in existing plants. In this study, a new operation methodology for auxiliary bi-drum boilers has been developed to reduce the operational cost of the plant. Two new functioning modes have been defined as "hot standby mode" (HSM) and "fast hot startup" (FHS). Both of them will be studied using thermal dynamic calculations. In addition, Power Plant Simulation & Design (PPSD) commercial software has been used for dynamic performance analysis. Results show that auxiliary bi-drum boilers will be able to operate under those conditions only if some additional technological modifications are implemented. For example, automated burners that are adapted to current standards, feed water control valve capable of regulating the flow during HSM, automate superheater valve drains and a continuous blow down valve. This new operation methodology will result in energy savings and reduction in operational cost. (C) 2018 Elsevier Ltd. All rights reserved.