This report presents a comprehensive analysis and comparison of the levelised cost of energy (LCOE) for the following offshore floating wind turbine concepts: Spar-Buoy (Hywind II), Tension-Leg-Spar (SWAY), Semi-Submersible (WindFloat), Tension-Leg-Wind-Turbine (TLWT) and Tension-Leg-Buoy (TLB). The analysis features a generic commercial wind farm consisting of 100 five megawatt turbines, at a far offshore site in a Life Cycle Analysis (LCA) perspective. Data for existing bottom-fixed turbines, both jacket and monopile concepts are used as reference values for adaptation to the generic wind farm parameters. The results indicate that LCOE values are strongly dependent on depth and distance from shore, due to mooring costs and export cable length, respectively. Based on the findings, depth is the dominant parameter to determine the optimal concept for a site. Distance to shore, Load Factor and availability are amongst the significant factors affecting the LCOE. The findings also indicate that LCOE of floating turbines applied in large scale and in intermediate depths of 50-150 m is comparable to bottom-fixed turbines. Floating turbines for increasing depths generally experience increased LCOE at a lower rate than bottom-fixed turbines. An optimal site, situated 100 km offshore would give LCOE in the range of (sic) 82.0-(sic) 236.7 per megawatt-hour for the conceptual designs in this paper. (c) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.