Carbon capture from power plants holds the key to any significant reduction in CO2 emissions. This work considers the energy penalty related to CO2 capture from coal, natural gas and fuel oil-based power plants. We evaluate the minimum thermodynamic work for CO2 capture, and then estimate achievable targets. All the three modes of capture-combustion: pre-combustion, post-combustion, and oxy combustion, are considered. The low CO2 concentration in natural gas-based power plants translates into the highest capture energy per ton of CO2. However, the lowest energy penalty of 10% is obtained with pre-combustion capture in natural gas-based power plants (versus 17% for coal-based power plants). The highest energy penalty of about 20% is found for oxy combustion capture from coal-based power plants. In general, pre-combustion capture seems to provide the lowest energy penalties. (C) 2016 Elsevier Ltd. All rights reserved.