Optimizing ThinkPad Z13 battery life on Linux

After fine-tuning my ThinkPad Z13 laptop running Linux, I've significantly reduced power consumption, especially with light usage. Below is a breakdown of the setup and results, which may help others optimize their systems for better battery life.

Test baseline

Laptop: ThinkPad Z13 Gen 1 (AMD Ryzen 7 PRO 6850U, 16GB RAM, 512GB SSD)

• Brightness: 25% (light -S 25)
• Speaker: 50%
• Wi-Fi: On
• Bluetooth: Off (rfkill block 1)
• Window manager: Sway (Wayland)
• Browser: Ungoogled Chromium with VAAPI and native Wayland, no extensions

CPU and GPU tuning

1. Use kernel >= v6.5 for some new hardware supports, with amd_pstate active for better CPU power management, providing significant battery savings.
2. Use TLP >= v1.6 for some new hardware supports: TLP is essential for laptops, optimizing power usage with minimal intervention. Adjust EPP (Energy Performance Policy) to power-saving mode.
3. CPU governor: set the governor to powersave by default, reducing power consumption when idle.
4. AMD GPU power mode: set to low, optimizing power usage for the integrated GPU. Note that this has caused some graphical glitches on my machine in the past, but I don't experience them anymore. YMMV.
5. Undervolting: helps reduce power draw without sacrificing performance.

Some example configuration in NixOS:

{
  services = {
    tlp = {
      enable = true;
      settings = {
        CPU_DRIVER_OPMODE_ON_BAT = "active";
        CPU_ENERGY_PERF_POLICY_ON_BAT = "power";
        CPU_SCALING_GOVERNOR_ON_BAT = "powersave";
        RADEON_DPM_PERF_LEVEL_ON_BAT = "low";
        PLATFORM_PROFILE_ON_BAT = "low-power";
        DEVICES_TO_DISABLE_ON_BAT_NOT_IN_USE = "bluetooth wifi wwan";
      };
    };
  };
}

I also have a small script to verify these settings, you can find it here

Some gotchas

• Docker network interfaces may cause high power consumption. I disabled Docker on boot and set it to start on demand by socket activation:

{
  virtualisation = {
    docker = {
      enable = true;
      enableOnBoot = false;
    };
  };
}

• Firefox consumes more power than Chromium for some reason. I still haven't figured out why, so I stick with Chromium for now.
• Sway fractional scaling: avoid fractional scaling for now to reduce the graphical load.

Test Results

• Idle power usage: Less than 3W
• Light web browsing (up to 10 tabs, including Reddit, Hacker News, GitHub, etc.): 3-4W
• 1080p AV1 YouTube (30fps): 5W (example video)
• 4K AV1 YouTube: 7.5W
• Closed lid overnight: lost ~1% of battery, and powertop shows ~0.2W consumption after waking up.

With these tweaks, my battery consumption dropped from 10-12W to 2-5W. Although the machine feels a bit slower, I don't mind the slight performance hit for the significant battery life improvement, since I mostly use my laptop for light tasks.