Ultralight backpacking geekery: stoves

As a climber, I’m always looking for ways to lighten my pack weight so I can have more energy to go for bigger, more exciting peaks. I’ve always like the idea of alcohol stoves. Their weight is counted in grams not ounces after all. But I never took them seriously because they use considerably more fuel than a basic canister stove. The incredible speed of an even heavier JetBoil or MSR Reactor also made that type of stove an attractive choice.
Then I had a conversation with a couple of alcohol- and esbit-burning stove converts on Friday evening, which got me thinking about them again. I got to pondering the break-even point for stove systems (i.e. when carrying an alcohol stove becomes less weight-efficient than a canister or other option), and before long I was elbows deep in spreadsheets.

Previously, I’d just been calculating total weight of the two systems at the beginning of the trip. I like to have a hot drink in the morning and a hot meal and a hot drink in the evening. This means I’m boiling roughly 48 ounces of water per day. This nets out to roughly 3 ounces of denatured alcohol, 3/4 ounce of iso-butane for a basic canister stove, or 1/2 ounce of iso-butane for a JetBoil. On a four-day trip, the total starting weight of the various systems including fuel is as follows:

Alcohol Stove: 14.25 ounces
Basic Canister Stove: 14 ounces (includes a full 4-ounce canister)
Jetboil Ti Sol: 17.375 ounces (includes a full 4-ounce canister)

See what I mean? Using this calculation, the basic canister stove system wins. Why bother with the slow alcohol stove? 

It finally occurred to me, though, that this comparison didn’t take into account how far you have to carry the weight and the varying rate at which the systems diminished in weight as fuel is burned. For example, even though you have to take more fuel for an alcohol stove, the system’s weight decreases rapidly because it burns so much fuel. I got to thinking that a better way to measure this would be to calculate the “weight-distance” of a stove system. (I readily admit that I may be reinventing the wheel here and this how everyone already compares one system vs. another, but it was such an a-ha moment that I wanted to share just in case no one had thought of it before.)

The calculation would go something like this: If you carry one ounce for one mile, you get a value of one. If you carry one ounce for 10 miles, that’s 10. If you carry 10 ounces one mile, that’s also 10. You can extrapolate this over a period of days based on the base weight of your stove system, amount of fuel you need per day, and your planned hiking distance to give you a total value for the “weight-distance” of a given system for a particular trip.

I played around with spreadsheets this morning and came up with an example of a four day trip. For one person, the weight-distances (in ounces) of the three stove systems would be as follows:

1-person-stove-chartClearly, the alcohol stove is the winner. Under my distance assumptions, it is more than 11 pounds lighter than a basic canister stove system and 26.5 pounds lighter than a JetBoil. That is a lot! 

Spreadsheets are amazing things. What happens if two people are using the stoves, burning twice as much fuel?

 

2-person-stove-chart

 

All of a sudden, the basic canister stove is the lightest option by more than 12 pounds. Huh!

Finally, I added it all up for a three-person trip, because sometimes you only take two stoves when there are six people on a trip.

 

3-person-stove-chart

 

The basic canister stove is still lighter, but the JetBoil comes in a close third and will likely be the better option in spite of the weight because of the time required to boil water for three people.

Finally, I added extra days to the solo chart until the numbers flip-flopped and the basic canister setup became more the lightest option. It finally happened when the trip length got to be six days long – two days longer than I originally thought:

1-person-stove-chart-break-even

 

These numbers blew me away. What do you think? Does this calculation make sense? Is this how you’ve been calculating weight all along and I’m just now catching up?

4 comments for “Ultralight backpacking geekery: stoves

  1. Gilbert Hoffman
    March 4, 2017 at 8:06 am

    That is some fine geeking out. There are probably others that do spreadsheets as well. ( I know of at least one, and he does a spreadsheet for total items carried.) I usually just do some rough calculations on paper. But I have never done math for the alcohol stoves before. Which is pretty interesting considering I have some friends who did the PCT with an alcohol stove. Makes me wonder why they went with that option?

    Something else to consider is size: Looking at your photo, (and assuming you don’t have a smaller pot for the canister stove) the Jetboil is the smallest system. Imagine using that smaller system allows to use a 50 liter pack instead of a 60 liter pack, reducing pack weight by ~4oz. throughout the whole of the trip? Or for a more climbing related carryover attempt, a smaller pack that doesn’t get in the way as much when climbing 5th class rock.

    Also consider ease of use. A Reactor goes from pack to boiling water poured in the Mountain House in less than 5 minutes. And it is virtually unaffected by wind. Consider too the prospect of poor weather and cooking in the vestibule. Or add to the spreadsheet the prospect of melting snow? You alluded to this ease of use when bumping up party size to 3 and desiring less time to boil water. The quicker water boiling allows for more time to do night photography, enjoy bedtime tea, or scout the route for the following day.

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