An engineering-economic analysis of the behaviours of each of two pre-combustion gas-turbine combined cycles with CO2 capture (an Integrated Gasification Combined Cycle (IGCC) and an Integrated Reforming Combined Cycle (IRCC)) is described. Their economic performances have been evaluated in terms of the break-even electricity selling price. The results show that the proposed pre-combustion power plant efficiency values (37% and 43.7% for the IGCC and the IRCC respectively) are significantly lower compared to a conventional plant value (55.3%). The CO2 emissions of the latter are less than half those of the conventional plant. Introducing an hypothetical carbon tax equal to 50 pound/tCO2, the break-even selling price (BESP) for the proposed IGCC and IRCC plants is 4.40p/kWh and 4.10p/kWh respectively, while for the conventional plant amounts to 4.73p/kWh. A sensitivity analysis has been carried out by varying the most influential investment parameters. The analysis has revealed that, considering the uncertainties associated with these key parameters, a substantial risk that the BESP could exceed the first value obtained is so prominent in some cases to alter their ranking order with respect to the most competitive technology. The final part of the analysis is a Monte-Carlo simulation to determine the impact of simultaneous variations of all the variables, subject to uncertainty, on the break-even selling unit price for the generated electricity. From the simulation, it derives that the BESP value ranges from 3.13p/kWh to over 6.00p/kWh for the IGCC case with a 50% probability of exceeding the first value obtained (4.40p/kWh). In the IRCC case, the range of possible value for the BESP is from 2.85p/kWh to 6.10p/kWh, and there is a 60% probability that the actual BESP would exceed the first value obtained (4.10p/kWh). Copyright (c) 2013 John Wiley & Sons, Ltd.