Drawing 20A on 12V means 240W which on 110V is 1A and a bit (a bit more once you consider efficiency of the conversion).

The spec sheet says that it will draw 2.7A max on a 115V input.

The power supply will convert the high voltage low amps into low voltage high amps.

Drawing 20A on 12V means 240W which on 110V is 1A and a bit (a bit more once you consider efficiency of the conversion).

The spec sheet of the power supply you linked says that it will draw 2.7A max on a 115V input.

The power supply will convert the high voltage low amps into low voltage high amps.