If you plug the amp into the wall, you might decide to plug in everything there and not buy the device.
Seriously, these devices make up for not having a 30 amp circuit.
I ran 2 of them with 10 Gua wire and separate breakers.
Another trick is to run a construction extension cord from a socket on a separate breaker and split the audio amps. I demonstrate the difference with some bass dropping out when I only use one circuit.
If you have a 15 amp circuit, with other things on it, you absolutely need the device.