Dear Gunwant,
You could have given little more information about you and your requirement. Are you student or professional? Why have you raised this query? What is the nature of your industry? What is the output?
Plant efficiency depending on its output. For example, for crude oil extraction plant, number of barrels extracted per week/month, cost per barrel, number of persons employed per barrel.
Second example is about steel plant. The government run plant produces 10 million Metric Ton of steel by employing 100,000 persons. However, their competitor in the private sector gives the same output by employing just 10,000 persons.
Therefore, while raising query please note to give complete information.
Thanks,
Dinesh Divekar