I have the Max Burton 1800W unit that I use as an auxiliary burner when I need it. Against your 15K BTU burners, I don't think you'll find a significant difference in time to boil water, since those are some pretty powerful burners! Performance against standard range burners is significantly better, however. Check to see if a magnet will stick to the bottom of the cookware you plan to use; if it doesn't, you won't be able to use it on an induction burner.

Another vote for the Max Burton. Since I don't have gas, I can't compare it, but it does boil water very quickly. I've been very happy with mine.

Counter top (120V) units top out about 1800 watts, which will heat a pot of water about as fast as a 13k BTU/hr gas burner. To get the true power of induction, at least compared to a home "pro" gas range, you need 240V built in units.

Still a great purchase. Mine has a timer function that will shut off after xxx minutes -- great for cooking rice.

Before I got my Miele 36" Induction Cooktop, for over 2 years I used (and still have and use) a Circulon 120V, 1500w portable induction round burner. The smooth, black glass surface cleans up easily and the unit works great!!!