I had an old dell xps 15 laptop which used the i7 2630qm processor which I replaced with an newer lenovo y580 (i7 3630m) (because it overheated too much). The dell xps at idle usually used about 3-4 watts of power on the cpu, the lenovo uses about 4-6 watts. Both are at idle on maxmimum battery modes. Power measured using hw monitor. I thought ivy bridge used less power than sandy.