This paper presents a steady-state analysis of the isolated class-E² converter outside nominal operation. By transforming the isolated class-E² converter into the typical topology of the class-E inverter, the switching patterns can be comprehended on the parameter spaces easily. The output power and the power-conversion efficiency can be expressed as functions of circuit parameters such as coupling coefficient of the transformer, load resistance, and operating frequency. The class-E² wireless power transfer (WPT) system was designed and implemented in this paper for verifying the analytical expressions. The analytical predictions of system performance against coupling-coefficient and load-resistance variations agreed with PSpice simulation and experimental results quantitatively, which showed the validity of the analytical expressions. Comparisons between the class-E² and classD-E WPT systems are shown along with their discussions. Additionally, two application examples of the analytical expressions are introduced in this paper, which shows the usefulness of the analytical equations.