Abstract We performed a study to determine whether flue gas bypass and solvent storage can increase the profitability of a power plant equipped with post-combustion carbon capture technology. By increasing flexibility, these technologies allow increased output when electric energy prices are high. We used the Integrated Environmental Control Model to characterize cost and operational parameters of a pulverized coal (PC) plant with both amine and ammonia carbon-capture systems, as well as a natural gas combined cycle plant with amine capture. We constructed profit-maximization operating models with both perfect and imperfect information about electric energy prices in a large electricity market in the Eastern United States. We optimized the size of the regenerator and solvent storage vessels to maximize profitability. Results indicate that the profitability benefits of flexible CCS range from 0 to 35%. Most of the potential benefit is capital savings from allowing the regenerator to be undersized. The benefits of flexible CCS were found to decline with increasing CO 2 prices, with steady-state units preferable above a CO 2 emissions price of $40/tonne. Flexible CCS was never optimal when the overall plant was profitable. While flexible CCS can boost profitability under policies that force plants with CCS to be built even where they are not profitable, it is less relevant under market-based policies that incentivize CCS through CO 2 prices.