Electric supply is essential for any economic growth. The electricdemand growth requires the increase of the installed capacity to meet theconsumption. Another alternative is the better use of installed capacity.Demand Side Management CDSM) has been increasingly adopted byutilities as a substitute for huge investments and as a method foroptimization of resources use. DSM is the planning, implementation andevaluation of .rility activities that are designed to encourage consumers tomodify their electricity consumption patterns with respect to both the leveldemand and energy.The presented work introduces a demand side management systemusing the expert system technique. The system is not case oriented. It iscomposed of a main module which, based upon set of rules, and selects oneof many possible solutions to perform DSM. The system has been testedusing data from industrial and residential applications. It uses practicalexperience gained during implementation of energy conservation systems.The system also offers user flexibility together with performanceexpectation. It allows the addition of extra rules upon user needs.The system performs DSM according to one of the followingstrategies:Peak clipping.Energy conservation:Building automationEfficiency equipment.Valley filling.Load shifting.Load building.Flexible load shape.The increasing use of power electronics devices and equipment hasincreased the harmonic levels in several networks. Also the presence ofpower converter and static V AR compensator can lead to numeroustechnical problems in the power networks. Their adverse effects havenecessitated the present standards and guidelines pertinent to tolerablelimits of current and voltage harmonic.