Hi there,
First we need to know what kind of power consumption we are talking about.
There is leakage (or static) power dependent on the cell size, or ultimately the transistor size. Dynamic power is dependent on switching (see the famous formula for dynamic power.... alpha*V^2*f). Internal power relates to switching inside the cell.
The values for dynamic and internal power provided by Genus and Innovus are usually garbage as these are strongly dependent on the input data waveforms. You have to give VCD file to the tools (or other format) to have correct answers. Otherwise, the tool will calculate an estimate based on its default switching settings.
For Sign-Off precision you need to run Voltus. You will need to create libraries with power data for Voltus first and after that you can analyze your design with specific VCDs...
Shlooky