Usually anything under 1500VA will typically use a standard 15A circuit or outlet. Do you know what L5-20R looks like? How about L14-20R? The images below will help you to identify the plug or outlet type that you are looking for.
UPS plug connector types
One of the things that must be considered when installing a UPS is your power requirements.

R-15R

R-20R, UL

5-20R, CUL

L5-15R

6-15R

6-20R

IEC-320

L5-20R

L5-30R

L6-20R

L14-20R

L14-30R