Larger wind turbines are believed to be advantageous from an investment and installation perspective, since costs for installation and inner cabling are dependent mainly on the number of wind turbines and not their size. Analogously, scaling up the turbines may also be argued to be advantageous from an operation and maintenance (O&M) perspective. For a given total power production of the wind farm, larger wind turbines give a smaller number of individual machines that needs to be maintained and could therefore give smaller O&M costs. However, the O&M costs are directly dependent on how failure rates, spare part costs, and time needed by technicians to perform each maintenance task and will develop for larger wind turbines. A simulation study is carried out with a discrete-event simulation model for the operational phase of an offshore wind farm, comparing the O&M costs of a wind farm consisting of 5 MW turbines with a wind farm consisting of 10 MW turbines. Simulation results confirm that O&M costs decrease when replacing two 5 MW turbines by one 10 MW turbine, if the total production capacity and all other parameters are kept equal. However, whether larger wind turbines can contribute to a reduction of cost of energy from an O&M perspective is first and foremost dependent on how the failure rates and maintenance durations for such wind turbines will develop compared to 5 MW wind turbines. Based on the results of this analysis, it is concluded that higher failure rates and maintenance durations rapidly are counterbalancing the benefits of larger wind turbines.