It’s easy. All you need is to find out the electricity tariff in your area. Here is the link of current tariffs in India http://www.bijlibachao.com/news/domestic-electricity-lt-tariff-slabs-and-rates-for-all-states-in-india-in-2016.html
Now that you have the tariff rate, it is time to calculate your energy consumption.
You can have four 100W Bulbs and you will use them for 6 hours each day.
You also have four fans each of 60W and they are used for 8 hours per day.
Your total energy consumption per day will then be 4x100x6 + 4x60x8 = 4320 Wh
Monthly consumption = 4.32×30 =73.92 Kilowatts =73.92 Units (1KWh =1 unit).
If you stay in UP, your tariff will be 4.4 Rs/Units
The total cost of the project will be 73.92×4.4=318.72Rs