Realtek NIC uses over 1 Watt with no traffic

[Paul Menzel]

Dear Linux folks,


Using Ubuntu 18.10, Linux 4.18.0-11-generic, PowerTOP 2.9 shows, the NIC 
uses 1.77 Watts. A network cable is plugged in, but there is no real 
traffic according to `iftop`. Only an email program is running.

    $ lspci -nn -s 3:00.1
    03:00.1 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. 
RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] 
(rev 12)

Is that a measurement error, or does the NIC really need that much power?

> Der Akku meldet eine Entladungsrate von 10.2 W
> Der verbrauchte Strom ist: 0.00 J
> GrundsÃtzlich benÃtigte Energie wird auf 10.5 W geschÃtzt
>
> EnergieschÃtz.    Auslastung     GerÃtename
>   7.03 W      4,9%        Display backlight
>   1.77 W      0,0 pkts/s  Netzwerkschnittstelle: enp3s0f1(r8169)

Letting it run for a while, the value even grows to 3.5 Watts, but
closing and starting PowerTOP, it goes back to 1.7X Watts.


Kind regards,

Paul