1. Simulation Based Approach
2. Non Simulative Approach or Vectorless Approach
Again at two stages
1. RTL Level
2. Gate Level
Depending about ur intent u can select any tool
1. Synopsys Power Compiler or Prime Power
2. Sequence Power Theater ( Not CoolTime , its not Power estimation tool as stated above )
I stand by Sequence's Power Theater because it not only estimates Power at both RTL as well as gate level but can also go by both simulative and non simulative approach .
Another feature that makes it unique is its ability to select the part of RTL code that leads to more power dissipation .
Azuro's PowerCentric provides a full-chip dynamic and static power analysis driven by activity, and at the gate level. It can also take RTL simulation activity as an input, even though it's analysis is at the gate level.
For vector less power analysis PT-PX stands tall but you can use prime power also
input files - For VCD flow (post and pre layout) - SPEF, netlist , VCD
for vector less flow -- netlist (but it will give only approx value but easy to use)