Ocean wave energy has significant technical potential but limited full-scale deployments and technology convergence. Consequently, guidelines for developing wave energy converters (WECs) are still developing themselves, especially around experimental uncertainty analysis (UA). To develop a comprehensive WEC-specific UA methodology, we conducted a 1:30 scale experiment of a case study oscillating water column (OWC) WEC. This paper presents the methodology, which describes UA principles and means to identify parameters causing uncertainty, and demonstrates new WEC-specific UA methods: general uncertainty analysis (GUA), the Monte Carlo method (MCM) for uncertainty propagation, and Type A and Type B uncertainty evaluation. Results show the expanded uncertainty averaged +/- 16% for capture width ratio and +/- 6% for wave loads; Type B uncertainty tended to be slightly larger than Type A uncertainty; and uncertainty in regular waves slightly larger than irregular waves. The MCM was found to be effective and efficient in uncertainty propagation. In general, given WECs tend to maximise motions, use a power take-off system, and must survive storms, WEC model tests may be especially susceptible to uncertainty due to nonlinearities and modelling complexities. In conclusion, UA should be carried out in WEC model test experiments. We close with recommendations for refining relevant international guidelines. (c) 2020 Elsevier Ltd. All rights reserved.