what is impact of discrete video card on battery life?

I am spec'ing out a computer that will be used for heavy social media work (Skype, IM, hefty multitasking, etc.) and don't know whether to include or avoid a discrete graphics card. Most of the video demands would be Photoshop, Second Life, and watching vidcasts. I'd go big, except this machine needs to have much better battery life than most gamers seem to expect, and I don't want to sabotage that with an unnecessary component. Will a dedicated graphics card (like a GeForce 8400M-GT or GeForce Go7600) noticeably shorten battery life? Or could the Intel GMA X3100 handle this stuff without trouble?

 

Integrated video cards have superior battery life compared to discrete cards but the difference isn't that significant that your PC shuts off on battery power after an hour. You can always adjust the power settings on your OS to help maximise battery life, but bear in mind if you're doing anything heavier than word processing or internet surfing on battery you shouldn't have such high hopes on performance when running off a battery.

 

youre always going to get much better battery life with integrated graphics

 

Any rough but quantitative-ish illustrations as to how much worse battery life is with discrete graphics? Are we talking shaving 10-20 minutes (off, let's say, a 4 hour battery life...that'd be what, 8%?), or something terrible, like shortening battery life by a third?

(Btw, thanks for those quick responses!)

 

Not many laptops last 4 hours on battery. Say on average a laptop with 2.5 hours on an integrated card watching a movie on battery would be shortened to 1.5-2 hours for an equivalent laptop with a dedicated card doing the same task.