Hello Sanjay,
Our experience is that the PLL's power consumption is fairly low as compared to the clock network it is driving in most cases. To get a sense for the amount of power the PLL consumes as a function of the VCO frequency, download a copy of the Early Power Estimator spreadsheet for the device you are interested in
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For a more detailed analysis, grab a copy of Quartus and fire up a toy design with the PLL in it, and run it through the PowerPlay Power Analyser. The PLL models for 90 nm and 65 nm devices take into account your VCO frequency, M/N values, and counter settings.
Regards,
Paul Leventis Altera Corp.