Here is a nice little program made for Gigabyte motherboards,
dynamic energy saver.
It saves power and money by turning off CPU cores and throttling the CPU speed when the speed isn’t needed.
What’s more it really works, as I am able to monitor the computers power consumption from my power monitor gadget I can see the power being used drop.
In the pic below you can see a row of pistons and two off the cores have been put to sleep.