You have to be cautious on using power extension at home, it may lead to disastrous result.
Since S9 has Power Consumption: 1375W + 7% based from the specs.
You will be needing power extension that rated to handle 1400 or greater wattage.
source from:
https://www.thespruce.com/extension-cord-choices-1152867Extension Cord Wire Gauges, Amperage Rating, and Wattage
Wire Gauge Amperage Rating Wattage Rating Power Tool Used
#18 5 Amps 600 Watts Detail Sander, Drill, Jig Saw
#16 7 Amps 840 Watts Belt Sander, Reciprocating Saw
#14 12 Amps 1,440 Watts Circular Saw, Miter Saw, Router
#12 16 Amps 1,920 Watts Table Saw, Radial Arm Saw
AWG #14 would be a good choice.