X-bit Labs has published a big article in which they compare the power consumption of overclocked processors, you can check it out over here.
Processor power consumption is closely connected with their clock frequency. That is why when overclockers increase their system performance they sacrifice energy efficiency. But how serious this problem actually is? We tested nice different processors from Athlon II, Core 2, Core i3, Core i7 and Phenom II families overclocked to different levels and are ready to give you an extensive answer to this question.