Mik,
"…+ the lightweight plastic bottle for carrying the alcohol."
Each Esbit tablet has its own container made of a plastic bubble/blister pack with a foil backing. Assume a hiker boils two cups of water for a meal. If one tablet boils two cups of water then that hiker is carrying 1 container of Esbit per meal.
Say that same hiker carries a 16 ounce bottle of alcohol in a re-purposed spring water bottle. Assume that hiker can boil two cups of water on his alcohol stove using 1 ounce of alcohol. At what point would the individual containers of the Esbit tablets add up to the weight of the re-purposed water bottle?
On another thread concerning solid fuel tablet stoves it was noted that some hikers carry dedicated Ziploc bags to contain their fuel tablets and the associated odor. Add the weight of this bag to the individual tablet blister packs and the weight of the fuel bottle seems almost less than or equal to all of the associated packaging materials.
The weight savings between the two types of fuel shows up when you realize that an Esbit weighs 14 grams or 1/2 ounce. A fluid ounce of alcohol weighs 24.2 grams. Zero out the containers and you get a difference of approximately 160 grams or 5.7 ounces.
Alcohol stoves burn clean. Esbit leaves soot and residue on the cook pot and "stove". This usually means that the hiker has to separate his stove and cook pot from the rest of his/her gear. This adds in a stuff sack and or another Ziploc. There can be additional weight if the hiker carries some sort of cloth or pack towel to wipe the soot from the cook pot after use. My guesstimate is that the stuff sack, Ziploc and "towel" could add up to 2 – 3 ounces in weight.
Both systems need stoves, pot stands and windscreens. I weight is the only consideration Esbit wins but not by much IMHO. Factor in the sooty residue and the odor of the tablets and alcohol, even though heavier, becomes more attractive to some hikers.
Note: You could remove the tablets from their packaging and put them all in the Ziploc to create a larger weight differential between Esbit and alcohol.
The lighter option is to use a wood stove. You carry the stove, windscreen and pot but gather your fuel at each spot where you choose to cook. In that way there is no fuel weight to consider at all. But you will spend time gathering wood and a wood stove does soot up also.
BTW I compared alcohol to canister stoves and found that since the canister stove is usually about twice as fast as an alcohol stove the two systems are about equal in weight over say a two week trek.
Esbit is lighter but the inherent soot and residue make alcohol more attractive to some hikers.
Party On,
Newton