We had a offer for EFF1 from one manufacturer & IE3 from other manufacturer with significant higher cost compared to EFF1. As per the vendor Now IE3 is the latest standard for Premium Efficiency, gives attractive payback & EFF1 is nowhere around IE3 standard.

But my question is as per catalogue of EFF1 & IE3 efficiency levels are almost same, so considering the standard motor loading & Operating Hour, Operating KWH will be also be the same, saving also be the same. then how to differ between the two ? Are EFF1 manufacturer shows assumed efficiency figures irrespective of unmeasured losses which may be measured in case of IE3 ?

If IE3 is better then how to justify it?