The Marmot Hydrogen is a wonderful sleeping bag.
It’s best for summer trips and shoulder seasons.
An experienced backpacker can stretch it into colder weather, earning a great reputation among ultralight hikers.
I purchased the Marmot Hydrogen in the spring of 2019, in anticipation of a long hike on the Arizona Trail. It’s been my sole sleeping bag since then, with over 3 years of use.
It’s seen me through summer trips and winter trips alike. I’ve washed it in a front-loading washing machine (just once) with no ill effects.
After I have a little more disposable income, I plan to purchase a Feathered Friends bag (likely a Hummingbird 20) for a little more warmth and quality.
But until then, I’ve certainly been able to stretch the sleeping bag’s 30F rating to suit my needs, and plan to use it for summer trips long into the future.
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Marmot Hydrogen 30 Specs & Features
Weight: 23 ounces (27 ounces in Long)
Temperature Rating: 30 degrees F ( -1 C )
EN Comfort: 33.6 F (0.9 C)
EN Lower Limit: 23.4 F (-4.8 C)
Insulation: 800+ fill power goose down
Shape: Mummy
Length / Height: 72 inches (Long: 78)
Shoulder Girth: 61 inches (Long: 63)
Hip Girth: 56 inches (Long: 58)
Fill Weight: 10.9 ounces (Long 13.8)
Unisex – no Men’s or Women’s versions
No Short version – only Regular or Long
Nylon shell and lining
Includes Stuff Sack (6×12 inches, 5.6 liters)
Left Zipper, Full Length
2nd Zipper, 13 inches
Hood with draw cord
Internal zippered stash pocket
Hang loops
Choosing a Sleeping Bag: The Basics
Here’s a few notes to help you translate the specifications and features listed above.
Down vs. Synthetic
Goose down feathers are infinitely lighter and more efficient than synthetic insulation. Down compresses and packs to a smaller volume than synthetics, too.
The main drawback is that down loses its powers of insulation when it’s wet, whereas synthetic material will still keep you warm. Products made with goose down also tend to be more expensive than synthetic, and some folks may be allergic to the down feathers. Synthetic bags are easier to wash, too.
Down Fill Power
You’ll often come across a “fill power” rating for down. For example, the Marmot Hydrogen uses 800+ fill power down. This number is simply a measure of quality for the down feathers. Feathers with more loft (and therefore more warmth per ounce) receive a higher rating. 950 fill power is more efficient than 600 fill power.
Temperature Ratings: Traditional, EN and ISO Test Standards
Traditionally, sleeping bag temperature ratings have been determined by the manufacturer. For example, the Kelty Cosmic (a nice budget bag) is rated at 20 degrees because Kelty decided that 20 degrees is the lowest temperature at which the average sleeper will stay warm in the Cosmic.
Each brand used their own testing methods (and some still do). So in theory, a Kelty 20-degree rating could be equivalent to a Marmot 30-degree rating.
In 2005, Europe began standardizing temperature ratings through the EN system. ISO standards took over the system in 2017, but the testing methods today are basically the same as the original EN standard. So for our purposes the terms are interchangeable.
In the test, a heated manikin full of sensors is placed in the sleeping bag. A sleeping pad is underneath the dummy, and it is dressed in a base layer including socks and long underwear. Three temperature ratings are established. These are Comfort, Limit, and Extreme.
Comfort is the range at which the average woman should be comfortable and in a relaxed posture.
Limit is the range at which the average man should be uncomfortable and cold, in a curled posture, but not shivering.
Extreme is the absolute limit at which you can expect to remain alive, but not without suffering some effects of hypothermia.
It should be noted that a wealth of factors play in to your comfort in the real world, but it’s nice to have a standardized system in place today.
Mummy Bags vs Rectangular
This should be somewhat self-explanatory, but rectangular is your classic kids’ style bag, whereas a mummy bag is tapered to conform to your body shape, often featuring a hood with a draw cord that cinches tight, leaving little more than your nose exposed to the elements.
There’s also everything in-between, as many sleeping bags aren’t rectangular, but aren’t true mummy bags either.
Mummy bags are more efficient, and rectangular bags (and quilts) are more spacious and comfortable.
The Hydrogen is regarded as a true mummy bag. One can even dive deeper and start comparing shoulder girth and hip girth.
Fill Weight
The fill weight is a measure of how much insulation is used in the sleeping bag (in this case, down feathers).
My Marmot Hydrogen 30F Down Mummy Review (Reg)
Having owned and exclusively used this sleeping bag for over 2 years, I’m more than happy with it as a premium summer bag.
For the winter it leaves a lot to be desired, but if I lost this bag tomorrow, I would be happy to replace it with an identical Marmot Hydrogen. The Feathered Friends Hummingbird 30 would be a tempting replacement, with a weight savings of 2 ounces for that sweet, sweet 950+ fill power down. If I were looking for more of true summer bag at a better price point, I’d opt for the REI Magma 30.
I am 6’0 and 180 pounds, and the Reg version of the Marmot Hydrogen fits me perfectly. If I were any taller, though, I’d want the Long version.
I like the full length zipper for ventilation.
The biggest drawback for me the bag’s extra zipper. As I toss and turn, sometimes this zipper will pull itself open.
I’ve washed it in a front-loading washing machine with Nikwax down soap, and tumble dried with no ill effects.
The Best Summer Sleeping Bag
The Marmot Hydrogen shines best as a summer and three-season sleeping bag.
It’s weight of 23 ounces won’t break the scales for those warm summer nights, and the 30-degree rating is there for you after a high-elevation hail storm.
Summer thru-hikers on the Colorado Trail, JMT, and so on should look no further.
Likewise, this is a good fit for fast hikes on the Appalachian Trail and PCT, though many hikers will wish for something warmer for the coldest nights of the trip.
As mentioned above, if you’re looking for something a little more light (and less warm) at the same price, check out the REI Magma 30.
If you want something of nominally higher quality and greater warmth, check out the Feathered Friends Hummingbird UL30 or the Western Mountaineering Megalite.
As a Winter Bag
With adequate planning, an experienced backpacker can be somewhat comfortable in the Marmot Hydrogen, even when temperatures drop well below freezing (to the extent that ice is found in your morning drinking water).
I used this sleeping bag on a January backpacking trip without any serious discomfort. I was, however, prepared with plenty of extra clothes and a thin fleece liner. I was also sleeping in a tent, which helps.
One of my favorite tricks in recent years is the use of a lightweight camp pillow. This simple practice frees up extra clothes and material that can be worn overnight to help me keep warm.
Through this and a few other tricks (i.e. emptying my backpack and sleeping in it, and the old boiled Nalgene bottle), I’ve been able to stretch this into a 4-season sleeping bag.
Another justification in using the Marmot Hydrogen as a winter bag is this:
It’s easier to get up in the morning. If I’m wearing extra clothing overnight, it makes it that much easier to get out of my sleeping bag when it’s bitter cold. Early mornings in winter are a huge advantage, as it’s otherwise difficult to put in substantial miles with limited daylight hours (especially off-trail).
Marmot Hydrogen Comparisons (& How to Choose)
Here’s how the Marmot Hydrogen compares to some other sleeping bags. It’s interesting when you’re torn between bags that offer different temperature ratings – choosing my desired rating has always been my first step in choosing a sleeping bag.
After determining my desired rating, I then look for the most lightweight models that achieve that rating. Finally, I compare the costs and (depending on my budget) compromise on a sleeping bag that won’t break my back (in weight) and hopefully doesn’t break the bank, either.
vs the Marmot Helium
Temperature Rating: The Helium is rated at 15F, versus 30F for the Hydrogen.
EN Comfort Rating: The Helium is rated at 25F, versus 33.6 for the Hydrogen.
Weight: The Helium is 10 ounces heavier than the Hydrogen.
Fill Weight: The Helium’s fill weight is 20 ounces, versus 11 in the Hydrogen.
Fill Power: Both use 800-fill goose down.
Cost: The Helium is approximately $70 more expensive.
My Thoughts: I was surprised to discover that the comfort rating between these bags only varies by 8 degrees, especially when the overall rating shows a whopping 15 degree difference. On paper it appears that the Hydrogen is the better choice with only a nominal decrease in warmth, but in practice I can tell you the Helium is indeed a significantly warmer sleeping bag. The giveaway here is when you inspect the Fill Weight – the Helium has 20 ounces of insulation, 9 ounces more (almost double) that of the Hydrogen.
vs the Marmot Phase 30
Temperature Rating: The Phase 30 is rated at 33F degrees, versus 30F for the Hydrogen.
EN Comfort Rating: The Phase 30 is rated at 42F, versus 33.6 for the Hydrogen.
Weight: The Phase 30 is 6 ounces lighter than the Hydrogen.
Fill Weight: The Phase 30’s fill weight is 8.5 ounces, versus 11 in the Hydrogen.
Fill Power: The Phase 30 uses 850+ fill, versus 800+ fill in the Hydrogen.
Cost: The Phase 30 is approximately $85 more expensive than the Hydrogen.
My Thoughts: Despite my claims that the Hydrogen is my best sleeping bag for summer backpacking, it appears as thought the Phase 30 could be even slightly better. The Phase 30, however, comes at an additional cost of $80 for a weight savings of 6 ounces, not to mention less versatility than you’ll have with the Hydrogen.
vs the Marmot Phase 20
Temperature Rating: The Phase 20 is rated at 20F degrees, versus 30F for the Hydrogen.
EN Comfort Rating: The Phase 20 is rated at 33F, versus 33.6 for the Hydrogen.
Weight: The Phase 20 is 0.8 ounces lighter than the Hydrogen.
Fill Weight: The Phase 20’s fill weight is 13.5 ounces, versus 11 in the Hydrogen.
Fill Power: The Phase 20 uses 850 fill, versus 800+ fill in the Hydrogen.
Cost: The Phase 20 is approximately $145 more expensive than the Hydrogen.
My Thoughts: Without personal experience with the Phase 20, I can only say that it tries to be a better, more versatile version of the Hydrogen for keeping you warm in cooler temperatures. The overall weight of the 2 bags is interchangeable, as is (interestingly) the EN comfort rating, despite how Marmot rates the Phase 20 at 20F, versus the 30F rating for the Hydrogen. To its credit, the Phase 20 offers higher-quality down with a slightly greater fill weight. The extra cost, however, at over $100 coupled with numerous complaints about the zipper in the Phase 20 reviews sounds like it’s not worth it.
It’s also worth noting that the Phase 20 offers a dedicated women’s version, whereas the Hydrogen is just a single unisex offering.
vs the Western Mountaineering Megalite
Temperature Rating: The Megalite is rated at 30F, same as the Hydrogen.
EN Comfort Rating: The Megalite is rated at 32F, versus 33.6 for the Hydrogen.
Weight: The Megalite is 0.7 ounces heavier than the Hydrogen.
Fill Weight: The Megalite’s fill weight is 12 ounces, versus 11 in the Hydrogen.
Fill Power: The Megalite uses 850+ fill, versus 800+ fill in the Hydrogen.
Cost: The Megalite is approximately $125 more expensive than the Hydrogen.
My Thoughts: On paper it looks like the WM Megalite and the Marmot Hydrogen are virtually interchangeable. Western Mountaineering, however, has a reputation for workmanship and quality that’s 2nd only to Feathered Friends (some backpackers attest that Western Mountaineering is better). So in this case seems to be a simple question of whether the Western Mountaineering brand is worth the extra money.
vs the REI Magma 30
Temperature Rating: The REI Magma 30 is rated at 30F, same as the Hydrogen.
EN Comfort Rating: The Magma 30 is rated at 39F, versus 33.6 for the Hydrogen.
Weight: The Magma 30 is 3.5 ounces lighter than the Hydrogen.
Fill Weight: The Magma 30’s fill weight is 8.5 ounces, versus 11 in the Hydrogen.
Fill Power: The Magma 30 uses 850 fill, versus 800+ fill in the Hydrogen.
Cost: The Magma 30 is virtually the same price as the Hydrogen – $340.
My Thoughts: If you’re primarily looking for your best summer sleeping bag, I think the Magma 30 ever-so-slightly edges out the Marmot Hydrogen (and for that matter, all the other bags on this list). It hits a sweet spot in warmth, weight, and cost. Just be mindful that the Magma 30 is less capable of seeing you through colder temperatures than the Hydrogen.
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