"However, my experience over a range of upright stoves (different models, different brands) is that the variation in fuel consumption between stoves is actually less (in general) that the variation found between low power and high power for the same stove. Large changes in pot diameter also change the efficiency somewhat."
+1 Low power is the way to go, IMO/IME.
"I have considerable experience with the burner head used in the FMS-117T stove: Fire Maple have used it on several different models. It does have good efficiency. By way of example, I normally allow 30 g of fuel per day for morning tea and dinner for Sue and myself. On a 6 day trip last week with an MYOG stove using that same burner head I averaged 26 g per day."
Wince, but that's because I'm a guy that is used to wringing 7 days out of a 110 gram canister for 2 people. But that is due to a difference in cooking styles. We each get by with 12 oz of water, brought to near body temp in the sleeping bag overnight and then heated to drinking temperature plus a bit to allow for cooling, probably ~150 degrees.
"Well, yes, BUT that only applies when you try to boil the water away into steam. Just taking water up to 100 C does not incur that penalty."
True enough, if you can control it that precisely. Mostly, I just wanted to give the potential penaly some visibility, especially since I have heard so many references to "bringing water to a boil". It is certainly not an issue for me, given my above mentioned style.
"If you are trying to cook some sorts of rice or rehydrate some sorts of dehydrated foods (for instance), you do really need to hold the water at 100 C for some time. Just holding the water at 80 C (~180 F) simply will not (ime) get some sorts of rice or dehi soft. The water just does not seem to get into the food. Somer foods are worse than others in this regard."
Here things get a bit sticky, IME. For lower elevations this holds. At higher elevations, water will boil at temperatures well below 100* C. In this case, one would not only incur the fuel penalty, but their rice would be, shall we say, al dente. Most folks who hike at higher elevations therefore use only foods that can be made palatable at much lower temperatures, cous cous, cracked wheat, and dehydrated food that reconstitute at lower temps, etc. This is the audience I was addressing when I made my original comments about latent heat of vaporization, as many of them have mentioned bringing water to a boil in various threads. Even if they do not boil for long, there is a certain penalty, perhaps small but nonetheless real, to be paid unnecessarily for the small of water they vaporize, and in reality their food would likely reconstitute at a much lower temperature, saving even more fuel. I know this to be true simply because I cooked my meals for many years and found myself saving considerable fuel after I figured out that I didn't have to bring my water to a boil, or even close, to rehydrate potatoes, beans, cous cous, etc. FWIW