In this work, a mathematical model was developed, in three steps, to predict the expected precision between two identical co-located Ultraviolet (UV) pyranometers. The resulting model shows that uncertainty is high at low UV irradiance and stabilizes at higher levels. The model was validated with multi-year UV radiation data from a photochemical assessment monitoring station. The solution can be used to evaluate and set the threshold levels of data quality control procedures in solar radiation monitoring stations.