On a big, commercial Denali expedition, I start with a staggering 96 pounds (12 gallons) of white gas, which produces the 378 gallons of water needed for a 21-day trip. Of interest, 378 gallons of water weighs 3024 pounds, a statistic that makes it clear that water (and the requisite fuel and stove) is the most precious resource in the mountains. This fact of life in the alpine has kept me wondering why stove efficiency has long lagged behind other efforts to reduce the weight climbers must carry.
On expeditions in glaciated ranges I set up my kitchen by digging a big, deep pit and stretching a light, floorless tent over the hole. In bad weather I always appreciate that the stove heats up the kitchen, but I have spent literally hundreds of nights contemplating the fact that most of the energy that comes out of a traditional stove escapes before it can be used to make water. I dreamed of a stove that would work more efficiently–reducing the amount of fuel I need to carry. If all the heat that pours off a stove could be focused directly into the snow in the pot, no heat would be wasted. For many years, stove inefficiency was a problem that was largely unaddressed by manufacturers. Finally, a new generation of hyper-efficient stoves hit the market, and MSR’s Reactor is by far the best. In my experience, the Reactor reduces my fuel needs by 50 percent.
MSR has long made the stoves favored by guides. Their white gas stoves, especially the XGK and Whisperlite International, are the staples of most guided expeditions. But with small groups on long alpine routes, these white gas stoves are not efficient enough. Using a 80/20-percent blend of isobutane and propane MSR calls IsoPro, the Reactor is a much lighter cooking system.
With a weight of 1 pound, 2.8 ounces (532 grams), the basic Reactor stove comes with a 1.7-liter pot, a lid and a small sponge that is useful for drying the pot before stowing the stove inside it, and padding the stove during storage. The stove uses IsoPro fuel canisters that weigh 8 ounces each. The whole package is elegant and compact.
The included pot holds meals for two or three people. MSR also sells a 2.5-liter pot that works well for groups of three or four climbers. The pot is crafted from anodized aluminum that is shaped to maximize the transfer of heat from the stove and recapture the heat reflected by the pot. The pot itself is very sturdy and the heat transfer system is so well built and attached that it is all but indestructible. The plastic lid is transparent, so pot will still boil even if it is watched. The pot handle folds perfectly over the top to hold the lid in place while in your pack. The slightly concave base of the pot sits securely on the convex stove, and is easy to place even when my brain is addled from cold, altitude and exhaustion. The pot sits well on the stove and can be lifted during cooking, which was not possible with previous canister-stove models.
During summertime in the North Cascades, I typically budget 2 ounces of fuel per climber, per day if I am using a mixture of running water and partially melted snow. The stove puts out an impressive 9400 BTUs. This means water boils in just a few minutes, but it also means that each canister only lasts about 80 minutes. With this in mind, it is very important to make sure that the stove is never allowed to run when I am not actively cooking. The Reactor is easy to relight, so I typically turn it on and off many times while preparing a meal. Unlike white gas stoves, no priming is necessary. Once fully lit, the burner glows with the MSR logo. This is perhaps an unnecessary feature, but still cool the first time I saw it.
A requisite for any stove used in the alpine, the Reactor cooks very well in breezy conditions. The pot and stove nest together tightly, and both components have features that protect the flame from the wind. In fact, the stove is so efficient that use of a windscreen can creates a hazardous situation if the canister overheats and explodes. MSR warns users not to use a windscreen and I take heed.
Anything this well made has its limitations, and there are a few things that occasionally bother me about the design. When traveling ultra-light, I inevitably end up using the pot to scoop snow for making water. The handle is a little flimsy for this type of abuse. My handle has never broken, but it has been bent over time. As I scoop the snow, some of it is forced into the heat transfer system at the base of the pot, slowing the boil time a bit and creating extra steam.
The fuel canister operates in an upright position, so when it’s half-full or lower, my cooking times slow. If it’s in contact with the ground or very cold air, I need to continually re-warm the canister with my hands to reinvigorate the fuel. As to be expected, the price tag is steep. That said, I have actually paid retail to have one for my Northwest Mountain School and it was definitely worth the money.
The final downside is one the Reactor shares with all canister stoves; the canisters cannot be refilled and are harder to find than liquid fuel. The canister itself is heavy compared to the amount of fuel it holds, making up 33 percent of the total weight of the fuel package and can be a minor burden to pack out. The Reactor’s canisters are becoming easier to get in places like Chile, Argentina, Mexico and Nepal, but it is still not as flexible as liquid fuel stoves that can burn multiple fuel types including premium unleaded, kerosene, and benzene.
Despite these shortcomings, the Reactor is still the best efficiency-stove on the market. Its heat transfer system makes the stove incredibly fuel-efficient and a strong performer in breezy conditions. The Reactor is successfully designed for stability and is exceptionally compact and durable. I can’t help but give it a five-star rating.
Pros: durable; very compact; works well in some wind; efficient; elegantly put-together; has the perfect power and size for a group of two or three climbers.
Cons: base of pot can trap water in the heat transfer system; handle is easily bent if the pot is used to scoop snow; fuel canisters lose power when not completely full or cold; a bit bulky for a single climber; canisters cannot be refilled; stove does not accept multiple fuel types.