How much electricity will I save if I use the onboard graphics card [closed]

"How long is a piece of string?

Without knowing your graphics card (and sometimes chipset), this is impossible to say... and there are many many factors involved.

The graphics card companies do not usually say how much voltage a single card will take but your best bet is to look at the requirements they give for a SLI/Crossfire and deduct it from the minimum specification...

For example - ATI Radeon™ HD 5770 System Requirements

450 Watt or greater power supply with one 75W 6-pin PCI Express® power connectors recommended (600 Watt and two 6-pin connectors for ATI CrossFireX™ technology in dual mode)

Meaning, 600w + 150w (2x 75w 6 pin) is 750w for two cards, the minimum specification is 450w + 75w = 525w, so deducted is 225w per card.... This is a high end card, and I am not sure how accurate, but I am not sure you will get better details on power specification.

This being said, I have been impressed with motherboards that have embedded ATI graphics, they seem to be very good, however, the last time I ran tests (about 2 years ago), I saw with some Intel boards, by using just a cheap £20 graphics card, it seemed to speed up general system performance - I am guessing due to offloading from the chipset. I am sure that even a low end card would use more power than embedded, but you may want to experiment yourself."