the first is to use a simple average supply cost of desalination of m as a working estimate for the supply cost of desalination this figure is based on a benchmarking exercise of seawater ro desalination plants that led to a similar average supply cost and on previous studies that have taken an estimation approach to supply costs the supply cost is irrespective of technology type and feedwater because reported costs are not tractable the second method for calculating cost is to use an energy cost based method the first is electric energy that is produced from a large number of fuel sources including coal oil natural gas nuclear fuel photovoltaic solar and wind energy ro plants use only electrical energy while msf and med use some electrical energy thermal energy can be derived from many of the same fuel sources as electrical energy including oil and natural gas or from such alternative sources as solar thermal msf and med plants primarily use thermal energy while ro plants do not use any thermal energy water desalination report vol