Nouveau Driver Power Management Against The NVIDIA Blob
First up is the Nouveau vs. NVIDIA drivers being compared while each system was idling at the Unity desktop with Compiz enabled.
When idling, the NVIDIA driver across all four systems had consumed less power than the Nouveau driver. This though is not too much of a surprise with a noticeable decrease in power consumption for the higher-end graphics cards. With the lower-end GeForce 9500GT, the NVIDIA driver was not dramatically more power efficient than the community's reverse-engineered driver.
Interestingly, when using the NVIDIA driver its core temperature was higher than the Nouveau driver for the GeForce 8 series. For the GeForce 9 series, the core temperature was lower. This is quite odd that the NVIDIA driver produced a higher core temperature while being more power efficient, but perhaps there is a bug in the GeForce 8 series reverse-engineered thermal sensor code that is causing the core temperature to be lower than it actually is running.