If I were to use an extension cord on the 40 inch 1200 watt model, what gauge is required? I already own this cable. Would it work?
As Dave mentioned, you might not want 100' cord. I use a 14ga cord with no problems but it is only a 20' cord. I have seen cords catch fire on construction sites from drawing a high load over a long cord for too long.
A 1200 watt masterbuilt will only draw around 10amps so it "should" work on most quality extension cords. Also, the element will cycle on and off so it is not a constant 10 amp draw.
You could get a cord like this for $20 and be good to go:
This is the exact extension cord I use with my MES 30 Gen 1 and it works fine. I have two outdoor power outlets and use this for the front of the house outlet. Good recommendation, BMaddox.
As @DaveOmak said you have to take into account the wiring to the outlet in the first place. Wire sizes are typically based on 50' runs (depending on the local code). If your run is 200' total than 12ga might not be enough. That's why I always use a short cord with my electrics as I don't know the exact run to the outlet.