The real issue, as I see it, is not so much one of cost but one of available real BTU's to the kettle. I have used commercial electric burner elements that can do the job, but I was using them in a commercial kitchen. A two burner electric hotplate usually operates on 220V 3-phase current, much like an electric dryer. Now, even used these units will run you hundreds of dollars. Then the logistics of wiring, etc. High Gravity in OK sets up electric brew systems and has much more info than can be told in an e-mail.
I would think that the best one could do with a household electric burner would be mini batches of a couple of gallons.
Yeah that's a concern that i had and i was hoping that someone would know the comparison between output and BTUs