Renewable energy is playing an increasingly central role in the global energy supply due to decarbonisation and energy security aims. A vital aspect of renewable energy systems will be the predictability of the energy source, something that tidal stream energy can provide. The tidal sites suitable for energy extraction are by their nature turbulent, creating variations in the tidal energy converter (TEC) loads and affecting device durability. Developers use Blade Element Momentum (BEM) models to predict loading and improve designs of TECs. To simulate turbulence effects within these models, a synthetic flow field is generated using a combination of measured and assumed parameters. Inaccuracies in these parameters can lead to uncertainties in the simulated loads. This study investigates the sensitivity of turbulence characteristics to loads using a commercial BEM software. Variability in parameters shows a profound impact on the loads. Varying turbulence intensity resulted in a 90% change in fatigue loads for intensities ranging 2–24%. Length-scales showed a 49% decrease in loads across the range tested (5–70 m). A coherent flow field increased loads by 45% compared to a non-coherent flow. Hub-bending loads varied by 30% between different shear profiles, however varying the standard deviation profiles did not show notable effects. The results from this study emphasise the necessity for accurate turbulence parameter inputs to reduce uncertainty in device load modelling. It also highlights the importance of using realistic shear profiles as well as appropriate coherence models.