Before boxing my new CW keyer based on K3NG work, I measured the current consumption since I have not been able to find it online. With an ATmega32U4 (a Leonardo clone) it drains 32 mA, regardless it is powered at 5V or through the supplied regulator (RAW pin). If the power save mode is enabled in the firmware, current in my specimen drops to 3 mA, but the keyer is not functional. I had hoped for lower current.
The embedded power LED could be removed to save few mA.
Conclusion: an on/off button must be installed.