Since nothing is 100% efficient, to block a 1000 watt AC power feed to something, like a burner on an electric stove, you will have to spend another 1000 W to cancel it out. and since this will be ***horribly*** inefficient, the real answer probably will be over 10,000 W. Good luck with that. I suggest experimenting at the 1 W level and letting us know how it goes.
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