Maneesh,
There has been a lot of research into how many BTU's it takes to boil water. How long it will take varies by altitude. You can look this up on line. However, you probably wanted to know how much water boiling has been done with a
rocket stove. I believe there is a design on-line somewhere for a rocket institutional cooker made from a 55 gallon barrel. A lot of people keep a water pot on top of the barrel of their
rocket stove.
Our company offers a shippable core consisting of burn tunnel,
feed tube, and heat riser in three sizes. We have some designs covering how to use the J-Tube cores on our website, www.dragonheaters.com. We have an idea for a unit which would have a cooking surface over the heat riser and a small oven next to it for bread or pizza.
Ernie & Erica also have some designs. You could incorporate our shippable core into their designs.
Cindy