If your PC is not beeing used and its Switched On then set it to Hybernation Mode. This will save current.
Also use good power supplies this too will save your Electricity Bills. However good power supplies cannot be purchased with casing for Rs. 2,400/- 2,600/- since power supply alone will cost around Rs. 2,500 for 300W. These psu do not have energy wastage. You can get them from Us.
The Pentium D processor consumes more power. The LCD takes about 30W. This is 1/3 of the 17" CRT power requirement. The present Pentium Dual core consumes less power.
For bills to be around Rs. 20K then your units must be around 600+.