3600 kilo joules is equal to 1 kilowatt hour that is one unit.

You are using 15120 kilo joules per day

Therefore Delhi electricity consumption in unit is equal to 15120/ 3600 that is 4.2 units per day therefore if you take a one month of 30 days then the total consumption of electricity in units is 4.2 x 30 which is equal to 126