Alcohol weighs 0.789 gram per cubic centimeter (or per millilitre – same thing). I use about 7 ml to boil one (250 ml) cup of water or about 5-6 grams. If I used butane I would use perhaps only 4 grams as it has a higher heat coefficient.
However once I count carrying around the heavy metal canister and the much heavier gas stove, alcohol becomes significantly lighter than a canister stove especially on shorter (eg weekend) trips when I can perhaps carry as little as 100 mls of alcohol in a bottle which weighs maybe 10 grams. On longer trips I usually use a 500ml or 1 litre Platypus bottle which weighs about 20 grams.
For example, on my Dusky Track Walk last year which took ten days (unsupplied), I started with less then 600 mls of fuel. I had worked out exactly how much water I would need to boil. At the end I had less than 30 mls left over – I must have missed a cup of coffee there somewhere. Well, actually I also had three sachets of porridge – my emergency supplies in case I took another day!
The empty canister of a butane stove can weigh 150 grams, then there is the stove weight. A simple alcohol stove like this (or this) can weigh as little as 7 grams – if you only want to boil. A canister stove typically weighs around 80-100 grams. It is also impossible to take just the right amount of butane, and you never know when you are going to run out as it is impossible to judge how much is in the canister. Sometimes therefore you need to carry two canisters. This is just silly even if the gas is slightly quicker, more controllable and ‘looks’ more ‘professional’.
Apparently the only more weight efficient fuel – than alcohol) is hexamine (esbits). They are a lttle slower to cook with, but you can simmer with them though you might not realize it –as mentioned here. Generally I prefer a simmer type alcohol stove like this one – or this even lighter one you can make yourself.
The only lighter fuel option is a wood burner stove. I usually carry one as well as the alcohol stove – in case I run out of fuel (eg bottle leak – it has never happened to me) or I decide to stay longer than I thought (which has – often) or if I stupidly did not have a windscreen and it was very windy (everyone makes mistakes) so that I used twice as much fuel as I intended (We were all young once!).
I have a variety of choices here. In my hunting day pack (which is super-minimal I carry only my egg-ring stove (as I am only staying out in an emergency – or (planned) overnight. If I am somewhere open fires are banned and enclosed type stoves are mandated (some National Parks – though I believe the rule only exists to protect us from idiots – and nothing will!) then I have a gasifier type stove like the Bushbuddy or Suluk.
My everyday carry is a bare Caldera Cone – I do not worry about leaving a tiny burnt spot; I only camp in the trackless wilderness anyway – which only weighs at most 30 grams and doubles as a windscreen for the alcohol stove. I always carry a couple of spare tent pegs anyway which is all that is needed to sit your billy on. Wherever I go there are always twigs. Hope you enjoy your dinner as much as I do.