At SIGGRAPH 2014, Intel has demonstrated DirectX 12 on a Surface Pro 3 (i5-4300U).
The first demonstration shows the power savings of DX12, using Intel's Asteroids demo, has the FPS locked:
The second demonstration shows the performance boost while drawing the same amount of power:
Overall, the results show a ~50% decrease in CPU power consumption, or a ~50% increase in FPS on the same hardware running DX12.
For more information, check out the link.