Hello everyone !

I have no idea if I’m in the right community, because it’s a mix of hardware and some light code/command to extract the power consumption out of my old laptop. I need some assistance and if someone way more intelligent than me could check the code and give feedback :)

Important infos

  • 12 year old ASUS N76 laptop
  • Bare bone server running Debian 12
  • No battery (died long time ago)

Because I have no battery connected to my laptop It’s impossible to use tools like lm-sensors, powerstat, powertop to output the wattage. But from the following ressource I can estimate the power based on the Energy.

time=1
declare T0=($(sudo cat /sys/class/powercap/*/energy_uj)); sleep $time; declare T1=($(sudo cat /sys/class/powercap/*/energy_uj))
for i in "${!T0[@]}"; do echo - | awk "{printf \"%.1f W\", $((${T1[i]}-${T0[i]})) / $time / 1e6 }" ; done

While It effectively outputs something, I’m not sure if I can rely on that to estimate the power consumption and if the code is actually correct? :/

Thanks :).

Edit:

My goal is to calculate the power drawn from my laptop without any electric appliance (maybe a worded my question/title wrong?). While It could be easily done with the top package or lm-sensors, this only work by measuring the battery discharge, which in my case is impossible because my laptop is directly connected to the outlet with his power cord (battery died years ago).

I dug a bit further through the web and found someone who asked the same question on superuser.com. While this gives a different reference point, nobody actually could answer the question.

This seems a bit harder than I though and is actually related to the /sys/class/powercap/*/energy_uj files and though someone could give me a bit more details on how this works and what the output actually shows.

This is also related to the power capping framework in the linux kernel? And as per the documentation this is representing the CPU packages current energy counter in micro joules.

So I came a bit closer in understanding how it works and what it does, even tough I’m still not sure what am I actually looking at :\ .

  • @fuckwit_mcbumcrumble
    11•9 months ago

    What is your goal with measuring this? Be aware that power consumption is designed to spike and return low. Most modern laptops won’t run very fast with a dead battery. Even with a high wattage charger because the spikes are too intense. Even with the highest wattage charger.

    The average power estimates that hwinfo in windows gets me is pretty accurate, but even it can’t account fully for the spikes. I’m not sure what the best equivalent is for Linux.

    • @[email protected]OP
      1•9 months ago

      My goal is to calculate the power drawn from my laptop without any electric appliance (maybe a worded my question/title wrong?). While It could be easily done with the top package or lm-sensors, this only work by measuring the battery discharge, which in my case is impossible because my laptop is directly connected to the outlet with his power cord (battery died years ago).

      I dug a bit further through the web and found someone who asked the same question on superuser.com. While this gives a different reference point, nobody actually could answer the question.

      This seems a bit harder than I though and is actually related to the /sys/class/powercap/*/energy_uj files and though someone could give me a bit more details on how this works and what the output actually shows.

      This is also related to the power capping framework in the linux kernel? And as per the documentation this is representing CPU packages current energy counter in micro joules.

      So I came a bit closer in understanding how it works and what it does, even tough I’m not sure what am I actually looking at :\ .