As an engineering geek, I spend a lot of time considering just this sort of tradeoff. (Too much time if you ask my wife...) It's true that for longer trips, canister stoves become more weight efficient than most alcohol stoves. But, it is the stove's fault, not the fuel. Most alcohol stoves waste a lot of heat due to poor flame control. An efficient alcohol stove can be more weight efficient than a canister setup for any length trip. Of course, convenience, reliability, pot type, windscreens, phaseofthemoon, etc. come into play in the real world. But from a strictly theoretical/thermodynamic point of view:
Unless I botched the math, a 110g Butane Canister provides approx. 4900 btu and weighs about 7.0 oz full/3.2oz empty; it takes approx. 6.8oz of Ethanol to provide the same heat energy. (Methanol is less efficient.)
So, assuming a 1oz alcohol bottle, a .5oz alcohol stove, and a 3oz canister stove:
Alcohol: 9.3oz full/2.5oz empty/5.9oz average Canister: 10.0oz full/6.2oz empty/8.1oz average
Note that this comparision is worst case for the Alcohol setup and best case for the canister. For shorter trips, you still lug around the empty canister weight (and unused butane, unless you start with a partially empty canister), but you can take only as much Alcohol as you need.
Cheers,
Mike
PS  responding to questions below, "ounces" in this post are avoirdupois ounces (weight), not fluid ounces (volume).
Edited by MikeMartin on 03/09/2005 09:21:37 MST.
