This paper deals with the implementation and analysis of real-time energy monitoring of the transient state of the wire electrical discharge machining (WEDM) process. Recently, sparking frequency information has been applied to control of the WEDM process, making more stable and efficient machining. Experimental results, however, show the limitations and insufficiency of that method. Instead of using the sparking frequency monitoring method, the use of a real-time instantaneous energy monitoring system is suggested for interpreting the state of the WEDM process in more precise detail. The transient state of the WEDM process is analyzed in detail with the developed system, and a transient stability criterion of the WEDM process is suggested. FANUC Wire EDM Filters