This research investigates the maximization of the expected wind farm power output through optimizing the layout of wind turbines as well as their heights. A model for determining the wind farm layout in 3dimensional (3-d) space is introduced. The objective of the layout design is to maximize the expected wind farm power output. To estimate the wind deficit in 3-d space, a linear 3-d wake loss model is developed and a criterion for identifying wakes affecting on a targeted wind turbine is constructed. The proposed model is complex and, therefore, solved by an evolutionary strategy algorithm. A comparative analysis of the proposed model and a benchmark model is conducted. In the computational study, the design solution offered by the proposed model indicates that the expected wind farm power output could be increased by choosing wind turbines with different heights. (C) 2015 Elsevier Ltd. All rights reserved.