Demand for small-scale water desalination and power supply including the utilisation of renewable energy sources at off-grid and sites is rapidly increasing. Integrated systems for the simultaneous de-centralised supply of water and power at "water and power points" in many cases are the most appropriate solutions for settlements and industrial sites in sun belt regions with limited access to grid power and fuel supply. SimTech and ZSW are developing their software tools, IPSEpro and RESYSpro, for the prediction of technical, economic and ecological performance of water and power point systems including desalination and water treatment (membrane and thermal processes), renewable energy sources for power (e.g., wind and PV power) and conventional power generator (e.g., Diesel). A good example for a typical application of these tools is the reported design and performance analysis of a demonstration plant for seawater reverse osmosis (RO) desalination powered from renewable energy sources on the African coast of the Mediterranean Sea. The water and power point shall supply 300 m(3)/d and 240 kW electricity to a village. For the RO demand of 60 kW, a 200 kW wind turbine is integrated with a 300 kW diesel GenSet. The key results from the systems analysis are the renewable energy fraction, the costs of investment, O&M and replacements, the life-cycle cost and present value of the project and finally the levelised electricity and water costs.