Through extensive international collaboration, a standard test method and performance metric of no load and average efficiency have been established. For harmonizing the test method, the average efficiency is calculated based on 25% increments in output load from 25% to 100% and at no load or standby, the output power is limited to less than 0.5 watts depending on output voltage and other criteria. The first mandatory requirement by EPA in US was meeting efficiency Level IV legislated under EISA in 2007. In Europe, EU(EC)No270 Phase I went into effect around the same time. The requirements were very similar to Level IV.