Low Wattage here
Seems to be up to around 400watts.
Above that you usually have a round cord.
Double Insulated Zip cord is on TV's, DVD's, Mixers, Stick blendors, electric clocks, lamps, shavers, toothbrushes and the such.
Once you get above around 400watts, you get a thick round cord.
If an appliance is double insulated, you have a two pronged plug, otherwise (Excluding lamps) its a 3 pronged plug.