Why Netgear R9000 consumes more power than its competitors?

> This router consumes a whoofing 19 V = 3.xx A. [...]

   "="?

   19V * 3.16A = 60W

> [...] astonishing little as 12 V = 5 A. [...]

   12V * 5A = 60W

> [...] I don't understand these calculations that much [...]

   Clearly.

   What, in your mind, makes one of these 60W figures "whoofing", and
the other 60W figure "astonishing little"?

> How can I reduce its power consumption without disabling 5GHz. I don't
> need 2.4GHz & 60GHz. [...]

   Disabling a radio might reduce the power consumption a little.

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual.  Read.  Look for "Control the
WiFi Radios".  Further reading might not hurt, either.

   But how would you know?  Are you equipped to measure the power
consumption of a device like this?  See, for example:

      https://en.wikipedia.org/wiki/Kill_A_Watt

   But, if you don't know power when you see it, then it's not obvious
that a meter will help much.