The book proposes a new paradigm for power theory that can be used in power systems and electrical networks. This new approach links electromagnetic and circuit theories in a coherent way by taking a fresh look at the old debates of poynting vector and reactive power as well as offering a mathematically consistent and physically coherent interpretation of the power concept and the mechanism of power transmission. Seeing the advances in geometrical optics, quantum mechanics, and geometric algebra, the monograph illustrates that, to paraphrase Heaviside, there is no finality in the development of a vibrant discipline such as power theory.