The influence of Computational Fluid Dynamics (CFD) modeling techniques on the accuracy of fixed pitch vertical axis turbine power output predictions was investigated. Using Two-Dimensional (2D) and Three-Dimensional (3D) models, as well as the Baseline-Reynolds Stress Model (BSL-RSM) and the k-ω Shear Stress Transport (k-ω SST) model in its fully turbulent and laminar-to-turbulent formulation, differences in power output modeling accuracy were evaluated against experimental results from literature. The highest correlation was found using a 3D domain model that fully resolved the boundary layer combined with the k-ω SST laminar-to-turbulent model. The turbulent 3D fully resolved boundary layer k-ω SST model also accurately predicted power output for most rotational rates, at a significantly reduced computational cost when compared to its laminar-to-turbulent formulation. The 3D fully resolved BSL-RSM model and 3D wall function boundary layer k-ω SST model were found to poorly simulate power output. Poor output predictions were also obtained using 2D domain k-ω SST models, as they were unable to account for blade tip and strut effects. The authors suggest that 3D domain fully turbulent k-ω SST models with fully resolved boundary layer meshes are used for predicting turbine power output given their accuracy and computational efficiency.