Power plants are prime candidates to apply CO2 capture for final storage as a mitigation option for climate change. Many CO2 capture concepts make use of a sorption-desorption cycle to separate CO2 from flue gas or O-2 from air. These include commercial absorption processes, as well as processes using new sorbent formulations, adsorption, and high-temperature chemical looping cycles for CO2 and O-2. All of these new processes must confront the large scale of carbon flows typical in a power plant. In this work, a common mass balance for all of these processes is used to define a parameter that highlights the minimum sorbent performance required to keep sorbent makeup costs at an acceptable level. A well-established reference system for which reliable commercial data exist (absorption with monoethanolamine, MEA) is used as a technoeconomic baseline to show that some of the sorbents being proposed in the open literature might need to be tested under laboratory conditions for tens of thousands of sorption-desorption cycles before they can be further considered as viable options for CO2 capture from power plants.