I ordered a 12V 1A power adapter. The adapter I got provided 12.3V without any load, and a maximum of 0.74A. I can only imagine how low the voltage gets while under load, but it definitely won't hold 12V under load.
I ordered a 5V 1A power adapter. The adapter I got provided 5.2V without any load, and a maximum of 0.46A. I can only imagine how low the voltage gets while under load, but it definitely won't hold 5V under load.