This paper presents a post-processing extension to a Monte-Carlo based generation portfolio planning tool in order to assess the short-term operational implications of different possible future generation portfolios. This extension involves running promising portfolios through a year of economic dispatch at 30-minute intervals whilst considering operational constraints and associated costs including minimum operating levels, ramp rate constraints and generator start-up costs. A case study of a power system with coal, combined cycle gas turbine (CCGT), open cycle gas turbine (OCGT) and wind generation options highlights that incorporating operational criteria into the long-term generation investment and planning analysis can have operating, economic and emissions implications for the different generation portfolios. The extent of the impacts depends on the dispatch strategies; the carbon price; and the mix of technologies within the portfolio. As intermittent generation within power systems increases and carbon pricing begins to change the merit order, such short-term operational considerations will become more significant for long-term generation investment frameworks. (C) 2014 Elsevier Ltd. All rights reserved.