New equations covering a wide range of oil types are developed to estimate the treating rate and treating temperature for dual polarity electrostatic desalters and AC conventional electrostatic desalters in Iranian oil fields. Production of wet crude had been a growing problem that affected the quality of produced oil in Iran. Application of the correct technology and the installation of proper desalting facilities were required to solve this problem. Therefore, it was decided to install electrostatic desalting plants progressively in Iranian oilfields. By the end of 2004, more than 20 dealing plants wit a total capacity of 207,000 standard cubic metres per day of treated crude have been installed. The performance of the majority of these desalting plants have been tested and found satisfactory. It is expected that the rate of wet crude production will increase to 366,000 standard cubic metres per day in 2007. This study shows that a dual polarity electrostatic desalter may operate at a minimum crude oil inlet temperature, resulting in extra fuel savings and eliminating the need for a heating system in the vessel. In addition, the treating rate for a dual polarity electrostatic desalter is more than for an AC conventional electrostatic desalter.