This article is a report of experiments on the Jetboil MiniMo cook set’s backpacking stove, regarding its efficiency. This particular stove gets high marks across the outdoor community concerning its minimal fuel usage. So I’m quantifying this efficiency for the sake of future comparison to itself in different conditions or to other stove systems.
Experiment 2 is a more controlled, more precise, better quality study than Experiment 1; the latter having been run at a campsite with more rudimentary equipment, and not in lab type conditions. Therefore this second experiment is presented before the first below.
Experiment 2 – Controlled Environment in a Garage
After running my first fuel efficiency study on the Jetboil MiniMo, in Joshua Tree, I was able to tease out its limitations and repeat it in a more refined manner. In that initial experiment, I had found the highest efficiency was likely near the midpoint in the openness of the fuel valve, and thus I focused in on that for my more controlled runs. However, it turns out, the most fuel efficient run in this second experiment was that where the fuel delivery rate was the lowest (two 180° twists of the valve handle). This is more consistent with the idea that there would be less waste heat being dissipated from around the burner area of the stove, and bottom of the cooking pot.
Methodology
Equipment Used
- Jetboil MiniMo cook set
- Taylor Compact Folding Probe Digital Thermometer, model 1476-21
- Toprime Digital Gram Kitchen Scale (500g max capacity; 0.01g precision)
- Kitchen graduated measuring cup
- Apple iPhone timer
Experiment
The thermometer was turned on and allowed to measure the ambient air while the other equipment was being put in place.
The stove was attached to a medium sized can of JetPower brand IsoPro fuel, which is an 80/20 mixture of IsoButane and Propane. The stove/fuel canister combo was then weighed on the scale twice. Both numbers were noted and averaged.
240mL of water was measured out and placed in the Jetboil pot. After some time had passed the water’s temperature was measured in the pot and noted. The pot was then attached to the stove.
For each run of the experiment, the fuel valve was opened to various 180° rotational twists between 2 and 5, the igniter was pressed, and the timer was started.
The probe thermometer was then placed in the water and monitored until final temperatures of 99.2 to 99.4C° were achieved. Once achieved, the fuel valve was closed and the timer was stopped.
The stove/fuel can combo was then reweighed in similar fashion to its initial weighing.
The water was tossed out of the pot and a 15 minute rest period, to let the pot and stove cool to ambient temperature, was implemented.
This process was then repeated for different, noted twists of the fuel valve.
Comparison To Experiment 1
The methodology in Experiment 2 was the same as in Experiment 1, except I used a more precise scale, and had more consistent temperature readings, both for ambient air, and water, as a function of the laboratory type environment, where no solar energy gain was present. Further I was closer to sea level, and had no confounding wind to deal with. All this is reflected in the data below. Note how all the readings and results form a much tighter consensus, than those from Experiment 1.
Fuel Efficiency Calculation
As in Experiment 1, fuel efficiency is defined by the following equation:
fuel efficiency = (mcδT)/(g*46,532) = 240*4.18*δT/(g*46,532)
At above the boiling points of both isobutane and propane, their combined energy density for a 80/20 mixture is defined in the following manner:
0.8*45,590J/g+0.2*50,300J/g = 46,532J/g
Collected Data
| Number of Valve Twists | Grams of Fuel Used | Time to Final Water Temp (seconds) | Initial Water Temperature C° | Final Water Temperature C° |
|---|---|---|---|---|
| 2 | 3.02 | 127 | 26.2 | 99.4 |
| 3 | 3.25 | 70 | 26.3 | 99.3 |
| 4 | 3.11 | 78 | 26.3 | 99.0 |
| 5 | 3.11 | 74 | 26.4 | 99.2 |
Ambient Air Temp
The ambient air consistently stayed at 27.8 and 28.2C° throughout the experiment.
Calculated Values
| Number of Valve Twists | Energy Needed To Raise Water Temperature (J) | Inherent Energy In Fuel (J) | Efficiency |
|---|---|---|---|
| 2 | 73,434 | 140,527 | 52% |
| 3 | 73,234 | 151,229 | 48% |
| 4 | 72,932 | 144,715 | 50% |
| 5 | 73,033 | 144,715 | 50% |
Discussion
Because the data and results in this experiment enjoyed such a tight consensus between runs, I’m going to state that there is a strong likelihood that the fuel efficiency of a Jetboil MiniMo stove and cook system is around 50% at ambient air temperatures around 28C°, or summertime conditions. (28C° also encompasses Spring and Fall conditions in Southern California.)
This result is quite variant from Experiment 1, which showed up to 86% fuel efficiency, such being a function of the imprecise measuring scale I was using to weigh the fuel. This imprecision quantized the fuel use for some of Experiment 1’s runs at 2 grams, which in all likelihood, in light of Experiment 2’s more precise fuel weighing, were actually 3 to 3.35 grams. This then produced a smaller inherent energy number for the fuel in multiple runs, and thus erroneously larger efficiency results.
Revising Experiment 1’s Results
Correcting Experiment 1’s fuel usage with numbers consistent with Experiment 2, we can revise its results as follows:
| Twist Number | Energy Needed to Raise Water Temperature (J) | Inherent Energy in Fuel (J) | Stove Efficiency |
|---|---|---|---|
| 1 | 73,033 | 139,596 | 52% |
| 2 | 79,654 | 140,527 | 57% |
| 4 | 79,855 | 144,715 | 55% |
| 7 | 81,159 | 151,229 | 54% |
| 7 | 74,738 | 151,229 | 49% |
The results are still a little on the high side, but more congruous with Experiment 2’s findings. One would think these numbers would be lower than Experiment 2’s, under less ideal conditions for the stove.
Had I timed the stove’s operation to final temperature, rather than to a visual rolling boil which occurred before such, I would have gotten longer times in general, and could have used these to refine fuel usage and inherent energy ((t_average1/t_average2)*inherent energy = corrected inherent energy) in the above results.
Alas I was making things up as I went, and didn’t think about it until I was finished with the lab work on Experiment 1 in Joshua Tree.
Conclusion
At ambient temperatures around 28C°, the Jetboil MiniMo cook set’s fuel efficiency is around 50%. The result’s range held tightly to this number at 48-52C°, indicating there is a high probability that this is the true efficiency for the stove system.
Experiment 1 – Indian Cove Campsite, Joshua Tree National Park
How efficient is a Jetboil backpacking stove at transferring its fuel’s energy to the heating of water? The Jetboil MiniMo stove may have a stunning efficiency of up to 86%, based on my initial experiment with the stove at Joshua Tree National Park during the early Fall, when ambient air temps were in the high 60’s and low 70’s Fahrenheit. Based on the data I collected, the stove’s efficiency is likely somewhere between 39 to 86%. However there were many confounding factors during the experiment that necessitate its rerunning in a more controlled fashion, with more precise instrumentation.
Methodology
The Jetboil fuel canister and stove were weighed using a digital kitchen scale before and after each run of the experiment. 240mL of water was measured out, its temperature taken with a digital thermometer, and heated to a rolling boil inside the Jetboil MiniMo cup. The temperature was again taken right before extinguishing the stove, and the time was noted on how long the water took to achieve a rolling boil with an iPhone timer.
The stove and cup were then allowed to cool back down to ambient temperatures, and another run would then occur, where each had its own unique variance on how much fuel was being dispensed by the regulation valve, counted as ‘twists’ of the valve handle, where 1 twist was equal to a 180º turn. Runs were accomplished at 1, 2, 4, and 7 twists of the valve; 7 being the maximal opening of the valve. Runs were done in a randomized order, and the 7 twist run was repeated.
Efficiency was calculated based on theoretical energy needed to raise the water’s temperature, using the initial temperature, and temperature at boiling, and theoretical total energy of the Isobutane/Propane 80/20 mix based on grams used for a given trial run. These two numbers were found, with the former being divided by the latter.
q = mcδT = energy needed to heat the water
g*46,532J/g = available energy in the 80/20 IsoPro fuel mix at temps above both gas’ boiling points
energy density of isobutane = 45,590J/g
energy density of propane = 50,300J/g
Collected Data
| Number of Valve Twists | Grams of Fuel Used | Time to Boil (seconds) | Initial Temperature Cº | Final Temperature C° |
|---|---|---|---|---|
| 1 | 4 | 240 | 24.4 | 97.2 |
| 2 | 2 | 86 | 18.1 | 97.5 |
| 4 | 2 | 60 | 17.9 | 97.5** |
| 7 | 3 | 41 | 16.6 | 97.5** |
| 7 | 2 | 56 | 21.5 | 96 |
Calculated Values
| Number of Valve Twists | Energy Needed To Raise Water Temperature (J) | Inherent Energy In Fuel (J) | Efficiency |
|---|---|---|---|
| 1 | 73,033 | 186,128 | 39% |
| 2 | 79,654 | 93,064 | 86% |
| 4 | 79,855 | 93,064 | 86% |
| 7 | 81,159 | 139,596 | 58% |
| 7 | 74,738 | 93,064 | 80% |
Discussion
Below I will discuss the confounding variables that arose while trying to run this experiment at camp.
Fuel Weighing Scale’s Imprecision
One of the largest confounding variables in this experiment was the imprecision of the kitchen weighing scale used, which could only read the fuel weight to the nearest gram. Had the scale been able to weigh the fuel to the nearest 100th, or even 10th of a gram, the efficiency calculations would be a lot more nuanced.
Case in point, during one run of the experiment where the fuel delivery valve was opened to its maximum and the scale read a 3 gram usage. However during the replication of that same run, again with the valve fully open, the scale read a 2 gram usage, even though the time to rolling boil was longer. I suspect in reality these two values are much closer together. Or they could be the selfsame value being confounded by the scale’s rounding algorithm, and the fuel’s non-whole number initial starting weight on each trial, which can’t be detected, due to its imprecision.
If in reality, the usage was in the mid 2-handle range, such would yield efficiencies in the 60 to 70% range. This would be expected as there should be a loss in efficiency at the fuel’s maximal delivery rate, where more waste heat would be generated.
Solar Related Ambient Air and Water Temperature Gain
As I was obligated to spend 15 minutes or so between runs of the experiment, letting the pot and stove cool down, this meant that the morning sun had more and more of a chance at heating the ambient air and water source I was using. The initial water temperatures varied over a wide range due to this, from 16 to 24C°.
Altitude Related Boil Temperature
Indian Cove campground in Joshua Tree is 3,200 feet above sea level. This means water is going to boil at between 96 and 97C°. While this could mean less fuel is used, this still affects my calculation regarding energy needed to raise the temperature of the water to boiling. These values would be higher, were I to repeat the experiment at sea level, where water boils at 100C°.
Lowest Setting Does Not Achieve Rolling Boil
In my last experiment, comparing the efficiency of the Jetboil MiniMo stove to that of a GSI Outdoors Glacier stove, during a controlled windy condition experiment, I used the time to rolling boil as one of my main endpoints. I wanted to do the same during this experiment, but unfortunately the lowest setting on the MiniMo doesn’t let the water reach a rolling boil, but instead one that is more moderated in nature. It was at that point, I decided to capture temperature values of the boiling water, as I figured the water may be achieving a similar temperature during this run, compared to the others, regardless of its ability to boil in a more chaotic fashion.
Though the lowest setting allowed for the water to moderately boil at the 240 second mark. It didn’t achieve the over 97C° temperature until 320 seconds into the boil, which is when I extinguished the stove. Hence more grams of fuel were used than were needed to achieve a boil, confounding the results for this particular run.
Conclusion
This rudimentary experiment with the Jetboil MiniMo stove shows that it can achieve up to 86% efficiency, when used at camp. It further shows that the most efficient settings on its fuel rate control valve are likely somewhere in the middle, between maximum and minimum fuel delivery (two to four 180° twists of the valve from the closed position).
Because of confounding factors, like an imprecise fuel weight measure, and both fixed and floating environmental variables, it is necessary to repeat this experiment under more controlled conditions. I have purchased a more precise scale and will repeat the experiment closer to sea level in a garage, where solar gain can’t affect the temperatures of the water, pot or stove, and where wind can’t interfere with individual runs of the experiment.
Further Reading
More information about the Jetboil MiniMo on my Jetboil page of this site. There you can find articles ranging from Jetboil MiniMo accessories to burner cleaning instructions to field operation of the stove.