Kernel option nohz_full in grub config.

Also disable hardware SMT as a kernel option in grub config. Then the cores can clock down way more often and L1 data cache size doubles.

XFCE and X11 tripled my laptop battery life vs. whatever Wayland+GNOME Ubuntu (2024?) brought by itself.

Powertop and tlp also help.

Happy camping.

EDIT: the lower heat dissipation also halved boot time. That one surpised me the most.

EDIT2: Disable "atime" with ext4 option "noatime". Saves a lot of power, heat, trimming, and re-writes on your SSD/NVMe.

For "faster shutdowns" manually run systemctl start fstrim.service. Not exactly sure why fstrim.timer seems unreliable.