Abstract
It would be difficult that an engineering simulation program becomes popular, if the user-friendly graphical user interface (GUI) couldn't be developed. EnergyPlus released in 2001 isn't a user-friendly program, but a simulation engine. However, several interfaces have been developed in the world, because anybody can free-download EnergyPlus. The present paper considers functions of four typical interfaces by comparing their feature and shows the outline of a developing Japanese interface of EnergyPlus.
