For laptops, Intel's i3 and dual-core i7 CPUs are both rated with a 35 W max TDP. However, it seems to me, with the i7 being more powerful, that the i7 would draw more power than the i3 on average, thus reducing battery life. Is this the case?
Engadget ran a test an Toshiba's new Portege R705 with an i3-350M and managed 4.5 hours of battery life on a 66 Wh battery. The laptop does come with an i7-620M as an option. What battery life should I expect with the i7 compared to the i3?
Well, power draw is going to be higher. For sure, you'll have less battery life. However, it's going to be a big drop. i7 for mobiles is just a faster clocked i3 with a few more features, it's in essence the same chip.
How much battery you'll sacrifice? it's hard to say, too many variables. Your best bet is to find out from another source that actually has the lappy.
But it won't be much, 15 minutes at worst possible case. Remember, TDP is not power consumption .