Given that we have seen the price of electricity sometimes jumping up to near 1 e per kWh here Finland, I have started to pay more attention to the power usage of my computers.
I have many headless Raspberry Pi units running all the time, so I first decided to investigate if there are any simple tricks on them to save power.
Many of the instructions I found were either obsolete (syntax changed etc.) or did not work. I have documented those settings and changes that I was able to measure or observe to have any effect. In the end, this was pretty futile effort. Pi does not consume much to start with, and any savings are even more marginal. But it's fun to tinker.
32-bit Raspberry Pi OS (bookworm) with:
The exactly same software (even SD card) was used on all models.
It seems the firmware enables TV out encoder when booting without an HDMI cable. Adding the following to config.txt shows 0.01-0.03 A (depending on the model) drop:
enable_tvout=0
It's also possible to verify that the video signal is not present using a monitor.
No measureable difference but you can visually observe the led is off after setting these in config.txt:
dtparam=pwr_led_trigger=none dtparam=pwr_led_activelow=off
NOTE: This does not work on Raspberry Pi Model B where the led is directly connected to the 3.3 V supply and is always on.
No measureable difference but you can visually observe the led is off after setting these in config.txt:
dtparam=act_led_trigger=none dtparam=act_led_activelow=on (Raspberry Pi Model B) dtparam=act_led_activelow=off (all later models)
Using these settings I have measured the following idle usage at 5 V (from highest to lowest):
It's worth noting that the first Raspberry Pi Model B and B+ are almost similar in specs, but there's a major difference due to power circuit redesign in B+.
Last updated: 2023-12-01 14:27 (EET)