Earlier quoted context omitted.
In the US, normal circuits aren't always 20A, especially in residential buildings, where they are more commonly 15A in bedrooms and offices. https://en.wikipedia.org/wiki/NEMA_connector
While technically true, the NEMA 5-15R receptacles are rated for use on 20A circuits, and circuits for receptacles are almost always 20A circuits, in modern construction at least. Older builds may not be, of course. That said, if your load is going to be a continuous load drawing 80% of the rated amperage, it really should be a NEMA 5-20 plug and receptacle, the one where one of the prongs is horizontal instead of ve…
This is not true. Standard builds (a majority) still use 15-amp circuits where 20-amp is not required by NEC.