Wave energy has the potential to be a major contributor to the global energy mix. It is estimated that commercial deployment of wave and tidal energy arrays could meet as much as 20% of the UK’s current electricity demand, with an installed capacity of 30-50 GW providing up to 16,000 jobs. However, the wave energy sector has not yet developed into a commercial industry due to several key challenges. One reason private investors have been reluctant to back the sector is that the uncertainty surrounding lifetime costs of wave energy arrays makes it difficult to obtain reliable estimates for overall cost of energy. In order to improve these estimates, a better understanding of the operations and maintenance (O&M) phase of wave energy arrays needs to be gained. This thesis presents an O&M simulation tool designed for wave energy arrays. The work presented uses the model to assess aspects of O&M strategies for two different types of wave energy converter. Uncertainty in the model inputs is also addressed by undertaking a series of sensitivity analyses. The methods and results presented in this thesis highlight the importance of using an O&M simulation tool to plan lifetime logistics for wave energy arrays and obtain realistic cost estimates. The work has also shown how an O&M tool can be used to identify critical components in wave energy converters, thereby helping to design the best device possible for the challenging marine environment. Understanding lifetime costs of wave energy arrays will drive the sector towards commercialisation, bringing wave energy a step closer to fulfilling its potential as a major contributor to global energy production.