GST Applicability on recovery of electricity charges

Dear Members ,

I have three queries relating to the same transaction.

Background : We are a  logistics & warehousing company providing the services for the same .

There are multiple customers/clients in the warehouses .

The electricity bill for the month is pro-rated and recovered from each customer based on the usage .

i)The HSN Code 998311 .Is this correct.If not ,is there an issue if GST is not charged

ii)Is  the recovery of electricity subject to GST

iii)A few customers are charged @ 1/sq ft consolidated for electricity ,generator back up diesel etc .Is this subject to GST.

Would appreciate if response to the above queries can be given.

Thanks & regards ,

Varun Monga