Unsteady load calculations for a large wind turbine using two blade element momentum (BEM) codes (FAST, HAWC2) are compared with results from blade resolved computational fluid dynamics simulations (FLOWer). This is to assess the performance of BEM under varying turbulence levels. Instantaneous and mean of power, spectral data and sectional blade forces are analysed for the three codes. The AVATAR research turbine with a radius of 102.88 m is used in this study. Based on comparisons, FLOWer and HAWC2 show a very close trend in mean power variations with different turbulence intensities. In contrast, FAST does not show a similar trend. This is conjectured to be due to different implementation in the BEM codes of the unsteady turbulence inflows, such as azimuthal variation of induction and dynamic inflow. The maximum error of CP is 6% for FAST and 1% for HAWC2 compared to FLOWer. (C) 2020 Elsevier Ltd. All rights reserved.