Story: I spent roughly 140 USD and a 20 hours or so integrating RPI 5 2g into my vehicle ODB2/12v system. Programming the PID data from ODB2 into something readable on the RPI is something I never want to do again, and the power issues on RPI (and, lack of support) have made it largely not worth it. Further, I thought I would come up with some use case to use the GPIO pins, (IE a hat for "mechanical" GPS, G force, etc.) but the headaches with power, programming and even the touchscreens I procured have made it not worth it.
I am now working on a basic NUC to replace that and it's a dream in comparison and cost next to nothing. GPIO access on RPI is negated as a "feature" by simply using USB on a NUC or similar mini pc for the same.
In comparison, my older laptop idles at around 5 W, even with multiple applications open. Similar experience more recently when looking at setting up a small home lab, the new Pi 5 seems to idle at around 5 W. A friend told me he has an Intel-based mini PC that draws less power. I'm tempted to try re-purposing an old phone, that should in theory do better.
I'd say the cheap ac to dc power supply it came with is no more than 80% efficient so 6.56W DC would be what I might expect to see if I peeled apart its DC feed side power cable and put a precise clamp ammeter around it.
Absolutely maxed out with stress-ng it's 24.6W at the wall.
You can take upstream kernel and u-boot and tf-a, just build it, flash it and have a working system for 10s of different boards from various manufacturers.