110volt kettle for decoctions?

It's been a while since I've posted in the electric brewing forum for the simple reason that, thanks to P-J's help, my 1/2 bbl electric brewery kicks ass! Anyway, as my brewing has progressed, I'd really like to begin doing decoctions for my German lagers. Has anyone thought about putting together a 110 electric kettle, to be used exclusively for decoctions? I'd like it to be super simple--maybe just a 1500 watt element mounted inside the kettle and a rheostat wired to the junction box on the side of the kettle? Would the rheostat idea work? Would the 1500watt element be able to boil a thick mash sample from a 15 gallon batch?

Bad idea IMHO. You'll be boiling the thick mash with the element and most likely scorching because there won't be enough liquid to carry away the heat.