my PSU is local made infact came installed with the cabinet , does it means if its 300 watt , its consuming 250 watts + power even in normal , without gpu system?
1) Power rating on psu is only for max watts that it can supply.
It does not mean that it will always use that much power. Generrally, cheaper psus have incorrect labels but anyway you dont need 300 watts.
2) So if you have a PSU that is rated 80% and you have PC that needs 100W, the PSU will use 100 * (100/80) = approx 125 watts.
Maybe a UPS might be able tell how much power is being drawn ( just guessing, i never had one).
But you can get approx power use by adding max / idle power use of each component and accounting for PSU efficiency. You can search for power use of each compenent on internet. I gave example link with sample system that used ~100 watt on load and about 50 on idle for i3
the wattage consumption I mentioned is for the configurtion which I recommended and not for your pc. for checking total wattage of your pc, u have to check your motherboard consumpotion plus consumption of each harddrives + consumption of dvd drives and any pci cards etc and add about 20% to the total. that will be the total cpu consumption
Maybe its valid thumbrule for your integrated one, i dont know, but in general - motherboard and misc consumption has nothing to do with cpu power usage. They all have to be added seperately, 20% will not work for all. Example a power hungry AMD 8 core processor will use much more than an efficient i3.