I went further and put something similar to this in our trailer:
100A AC LCD Panel Digital Power Meter Monitor Voltage KWh Watt Voltmeter Ammeter
(search ebay for that)
Connected it to the Progressive PT30C (hardwired version) on the output side (and put the ammeter coil on the output wire inside the PT30C).
This way you can see your voltage, and the power consumption at the same time. I mounted it in a small project box (most electronics stores have them) and used some 4 conductor 16 AWG SJOW wire to route it to from the surge protector to the device I mounted on the wall.
Make sure you put a fuse inline with the hot voltage wire.