Before we go over the test results let's first review what's happening when you put a flame under a pot full of water. Here's a page covering the transfer of heat, in fact you can plug in your own values and solve for various aspects of the formula. The components of heat transfer are: surface area, thickness, thermal conductivity, and the differences in temperature.
Each component contributes to overall heat transfer in its own way. The type of pot material makes a difference, aluminum having better thermal conductivity than titanium or stainless steel but not as good as copper. Thickness also matters, and of course the type and thickness also play a factor in how light and durable the stove is.
The temperature of the flame is an obvious one. If we are using the same fuel it becomes a matter of how much is released in a given time, the efficiency of the burn, and how evenly the flame is spread out. Still, there are theoretical limits to what a stove can do and I doubt if any manufacturer can claim to take the same amount of fuel and turn it into a flame that is significantly hotter than other stoves. Plus, adding heat doesn't always help, as we will see.
Then there's surface area. To put surface area in perspective think of a slice of toast and a pad of butter. The butter is our metaphorical flame and as we spread it across the toast it is sucked into the dry bread. If our slice of toast was the size of a half dollar the butter would quickly saturate the bread and we would have extra butter left over. If the toast was the size of a magazine we would end up with mostly unbuttered toast.
The thing you might not remember about spreading butter on toast and other surface area situations is that area is proportional to the square of the linear dimension. In other words if you double the toast size from 2x2 to 4x4 the surface area is now four times larger, making it an important factor in the equation.
Which brings us back to the pan of water with the raging inferno below it. If your pot area is too small (and/or a poor conductor of heat) a lot of the heat from the flame will go pouring ineffectively into the surrounding air. As an experiment bring your hand a few inches from the pot. Do you feel a high heat? (as opposed to warmth) That is waste heat. The stove burned fuel to make it and, obviously, it wasn't transferred into your pot of water.
The "ideal" stove would burn just enough fuel to produce the heat that the pot is capable of absorbing at that particular moment. Of course with that many elements in the equation "ideal" is a moving target, leaving tired backpackers cranking the heat full blast and hoping for the best.
Remember Jetboil's secret technology, the FluxRing? Well, that's a marketing word for "greatly increased surface area without having to lug a huge pot around." They've taken a whole bunch of surface area, folded it up, and put it into a small area, conveniently located in the path of the flame. Check out a car's radiator or look in the back of an air conditioner, they both use a similar method to greatly increase surface area without using up a lot of space.
Well, enough of my blabbering, let's get back to our regularly scheduled stove test...
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