This book is about fuzzy logic controller (FLC) and its applications in energy systems. It aims to give an insight into a clear understanding and design approaches of FLCs in MATLAB� and MATLAB/Simulink� environment. It includes a basic theory of fuzzy sets and FL to prepare the reader for a better understanding of fuzzy partitioning, fuzzy relation and fuzzy decision-making processing, which are required for designing FLCs. A fuzzy unit called fuzzy processor is developed and designed to be used as a fuzzy decision maker and a FLC depending on the application prob