The objective of this work is to determine the impact of sub-hourly modelling of a power system with significant amounts of wind generation. This paper presents the modelling of the Irish power system for a one year period at 5 min, 15 min, 30 min and 60 min resolution simulations using a unit commitment and economic dispatch model assuming perfect foresight. The work examines how much operational costs increase with more accurate resolution. Results show that increased temporal resolution captures more variability in system load and renewable generation, and is necessary to capture the inflexibilities of thermal units that lead to more realistic estimations in total generation costs. Significant cycling and ramping of units is also captured in higher resolution modelling that hourly resolution modelling is unable to capture. (C) 2013 Elsevier Ltd. All rights reserved.