In October, the Raspberry Pi Foundation released an updated bootloader/firmware for the Raspberry Pi 4 which dramatically reduces power consumption and overall temperatures on the Pi 4 by setting the USB controller and CPU into a more power-friendly mode.
I wanted to post here the instructions for checking the current version, and upgrading, because I have a large number of Pis to upgrade over time, and I needed a quick reference. For more details, check out the Raspberry Pi Documentation page Raspberry Pi 4 boot EEPROM.
Checking if the current bootloader is up to date
Upgrade system packages and install the
$ sudo apt update
$ sudo apt -y full-upgrade
$ sudo apt install -y rpi-eeprom
Check if an update is required:
$ sudo rpi-eeprom-update
If you see a difference in the output, you can restart to update to the newer version. If everything's the same, you're already on the latest version.