I recently got a new USB-C power tester, and my first use was measuring the power consumption of the PicoCalc (@ MMBasic console).
The lowest power consumption I measured was 0.4 watts with the display turned off and 0.44 watts with the display set to its lowest brightness level. At around 0.5 watts, the display reaches a brightness that is comfortably usable indoors to me.
One notable finding is the significant impact of the audio volume knob: Even without any sound playing, turning the volume knob to its maximum setting increases power consumption by about 0.3 watts. This nearly doubles the power usage at the lowest brightness. With maximum brightness (and volume turned down), I measured a consumption of 1.3 watts.
It would be interesting to see how these measurements compare when using other boards, such as the Luckfox Lyra. Please feel free to report the power consumption of your setups!