NEPLAN Electricity is a software tool to analyse, plan, optimize and simulate electricity networks. The user-friendly graphical interface allows the user to perform study cases very efficiently. The customizable software has a modular concept and covers all electrical aspects in transmission, distribution, generation / industrial networks. It suits also for renewable energy system and SmartGrid applications because all necessary models and simulation methods are integrated with a very high accuracy and performance. Besides steady state calculations, power quality and optimization aspects and protection design, the NEPLAN simulator allows to model wind and solar power plants with their controls for dynamic simulations (RMS/EMT) in detail and integrates also Matlab/Simulink models. The common database and the unique application programming interface simplify the integration of NEPLAN in external applications.