This paper presents a sample calculation of the benefits inherented in reducing sulphur dioxide (SO2) emissions for the Israel Electric Corporation (IEC) through a system approach. A methodology for calculating the benefits inherented in reducing various pollutant emissions has been formulated as well. This methodology was implemented for two sets of data, which describe a ''clean'' scenario and a ''polluted'' scenario through a model for long term optimal generation system expansion planning. The methodology described is suitable for calculating the cost of preventing the emission of SO2 and other pollutants as well.