Distillation, or condensation from a vapor, is the most widely used desalination process; freezing and thawing, electrodialysis, and reverse osmosis are also used. All are energy-intensive and therefore expensive; so, for this reason, it is generally used only where sources of fresh water are not economically available.

Currently, more than two billion gallons (eight million cubic meters) of fresh water are produced each day by several thousand desalination plants throughout the world, the largest producers are apparently are in the Arabian Peninsula.