I've been using a 1300 watt Suppentown induction cooktop full-time in my van for several months now, and it works great. I mainly use it for boiling water for coffee, and for basic cooking. As a result, I rarely have it on for more than 10 minutes at a time. The highest setting, which I use only for boiling water, draws around 85 DC amps, as reported on my Trimetric battery monitor. Takes about three minutes, which comes out to around 4 amp hours to make coffee. For most cooking, the 500 watt setting is fine, so the power draw is considerably less. If your cooking needs are as basic as mine, then I think an induction cooktop makes way more sense than a propane setup. Totally impractical, however, if you want to be able to simmer a pot for an hour or so.
Glenn
http://www.tosimplify.net