If the Central Government or the State Government is of the opinion that it is necessary or expedient so to do in the public interest, it may, by notification and subject to such conditions as may be specified in the notification, exempt any designated consumer or class of designated consumers from application of all or any of the provisions of this Act:
     Provided that the Central Government or the State Government, as the case may be, shall not grant exemption to any designated consumer or class of designated consumers for a period exceeding five years:
     Provided further that the Central Government or the State Government, as the case may be, shall consult the Bureau of Energy Efficiency before granting such exemption.