Thermoeconomy is a useful and powerful tool that combines thermodynamics and economics. It can evaluate how irreversibility and costs of any process affect the exergoeconomic cost of the product flows. The thermoeconomic analysis of a seawater reverse osmosis desalination plant with a 21,000 m(3)/d nominal capacity located in Tenerife (Canary Islands, Spain) is given. This analysis extends the exergy analysis performed in a previous paper where further details about features of desalination facility, flow diagram, equipment purposes and flows of the process are widely provided. The main result indicates that economics predominates over the thermodynamics aspect; thus the influence of the operational parameters on the unit cost of the final product is significantly limited. Reverse osmosis skid is the most influential equipment on both the thermodynamic and economic aspects. As well, pretreatment has a large influence on the unit cost of the final product, essentially due to O&M costs. The unit cost of external consumption and the annual real discount rate are the most influential parameters on the sensitivity analysis of the final product and the high-pressure pump efficiency the most important of the operational ones; conversely, membrane replacement is the least important among the parameters analysed.