Is it really required to remove the voltage regulator to save power?

[benhub]

Hi! The site about powering an Arduino Mini Pro with batteries suggests to remove the voltage regulator. But in the sparkfun tutorial about this Arduino I just read the following:

If you already have a regulated 3.3V source from somewhere else in your project, you can connect that directly to the VCC pin. This will bypass the regulator and directly power the ATmega328. Don’t forget to connect the grounds (GND) too!
https://learn.sparkfun.com/tutorials/using-the-arduino-pro-mini-33v/all

So, is it really required to remove the voltage regulator? Could the battery be connected directly to VCC? Does the voltage regulator use power when having the battery connected to VCC+GND?

[hard-shovel]

@benhub Short answers, No, Yes, Yes

The regulator will use power if connected.
If your circuit is power hungry then removing the regulator will have limited effect.
The sparkfun schematic on the article that you listed notes to disconnect the regulator for low power, so the advice is consistent.
Unless you are using the genuine sparkfun versions of the pro-mini where the jumper can be cut then physically removing the regulator is recommended.