We've recently renovated out kitchen, and due to a gas leak in the mains, had to go with something electric. There was no way we were going to go with a traditional electric cooktop, on account of them being crap. So I decided to fork out the extra and go with induction (I stovetop biab).
I was a bit worried about the power, with big volumes of water, but I can tell you it's not an issue. Bear in mind the cook top I went with, the burners, or hobs are 2300 watt each. They can also 'power boost' to 3200 watt. Here's a link to the one I went with, its electolux:
http://www.ebay.com.au/itm/Electrolux-EHD9...e-/290754112652
For the record, the Big W pots do work on induction. And a single burner will bring it up to boil, when full, from 20 odd degrees in about half an hour. That's with the boost on. Easily keeps it at a boil, on 8/10 power, with boost off after achieving a boil.
I read on another forum, before I bought the cooktop, that the cheap ebay portable ones (2000 watt or thereabouts) are just gutsy enough for 5 gallons, or 20 litres.
This particular electrolux cooktop has a function whereby you can place large pots over 2 cooking zones. I have a 32 litre pot that I also use for biab, and 2 elements on 8/10 have no problems bringing that volume to a boil in a reasonable amount of time.
Overall I'm pretty happy with the purchase. Very happy even. The lack of information on the net about brewing on induction had me really worried, but it's all good. For the record, my 32 litre pot is a 2 dollar shop special, thin as. Cost like 40 bucks. Magnets do stick to it though.
Oh and btw no affiliation with electrolux, just a happy customer.