Review: Marmot Hydrogen 30 Sleeping Bag

Ultralight Sleeping Bag
Marmot Hydrogen 30
$399, 1 lb. 9.4 oz./720g (regular)
Sizes: unisex regular and long ($419)

For backpackers prioritizing low gear weight who don’t tend to get cold very easily, a sleeping bag rated 30 degrees Fahrenheit can function as their go-to for most three-season trips. And Marmot’s Hydrogen 30 remains one of the perhaps three highest-quality and warmest ultralight mummy bags at this temperature rating, as I affirmed sleeping in it for two nights on southern Utah’s Owl and Fish canyons loop in early May and five nights hiking the Grand Canyon’s Gems Route in mid-April.

Just three of those backpacking nights that I slept in the Hydrogen 30 were inside a tent: one quite windy night in the high 30s F, with a below-freezing wind chill, in Owl Canyon, and two nights in the Grand Canyon. My four nights sleeping out under the stars included a calm night in the mid-40s in Fish Canyon and three nights with winds gusting up to 30 miles per hour at times and overnight lows in the 40s and 50s in the Grand Canyon. In every circumstance, I stayed perfectly warm, even partly opening the bag on the milder nights. I also slept quite well in this bag out under the stars for two nights in the 50s in Idaho’s City of Rocks National Reserve.

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The Marmot Hydrogen 30 hood.
The Marmot Hydrogen 30 hood.

The 800-fill down, treated with ExpeDry to make it dry faster if it gets wet, gives it a high warmth-to-weight ratio and an EN comfort rating of 36° F/2° C, limit rating of 27° F/-3° C, and extreme rating of -3° F/-19° C—while still weighing a modest one pound 9.4 ounces/720 grams (regular length).

Its weight trails close behind the very lightest and it’s warmer than all but a couple of them with which the Hydrogen 30 compares closely for warmth: As I wrote above, it packs enough warmth for nights that creep toward its temp rating (unless you sleep cold; see my “Pro Tips for Buying Sleeping Bags” for tips on that). And it stuffs down to a compact 4.6 liters/280 cubic inches/12.2×5.9 inches. When pulled from its stuff sack the Hydrogen lofts up to about three to four inches.

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The Marmot Hydrogen 30 with both top zippers open and the flap folded down.
The Marmot Hydrogen 30 with both top zippers open and the flap folded down.

This bag kept me warm on nights that fell within the temperature range that backpackers will typically encounter in summer in mid-latitude mountains and in spring and fall in the desert Southwest.

Warmth if boosted, of course, by the adjustable hood, which closes evenly and comfortably around my face and head, while the draft collar and tube along the zipper protected me from chilly air outside and strong, cool gusts when I enjoyed long, deep slumber under the stars.

On mild nights when I kept the bag partly open to ventilate, the short second zipper on the upper right side of the bag’s top side (opposite the main zipper) enabled me to fold a flap of the bag down off my shoulders and upper torso, like a blanket—a nice feature because opening the main zipper just on one side to fold a triangle of the top of the bag off you often just results in the flap flipping back over you. The anti-snag slider on the full-length main zipper (on the left) works well. The wraparound construction of the footbox also boosts warmth.

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The circumference measures 61 inches at the shoulders, 56 inches at the hips, and 44.5 inches at the feet—roomier than other leading ultralight, 30-degree bags like the Mountain Hardwear Phantom 30 and Feathered Friends Hummingbird UL 30 at a weight penalty of just a few ounces and a price lower than both. I found there’s plenty of space to move my feet around and stuff a little extra clothing down there to boost insulation and keep that clothing warm for morning. Its length is the standard 72 inches/183 centimeters (regular bag). An internal zippered pocket fits a smartphone to keep it out of the cold.

While the sizes are unisex, I think unisex sizing makes sense in sleeping bags because body shapes and sizes vary greatly within genders as much as between genders.

The Marmot Hydrogen 30 in southern Utah's Owl Canyon.
Testing the Marmot Hydrogen 30 in southern Utah’s Owl Canyon.

The 75 percent recycled, Pertex Ultralight 20-denier ripstop shell fabric, with a PFC-free DWR (durable, water-repellent treatment), blocked those strong gusts quite well when I slept under the stars.

For backpackers on a budget, the Marmot Lost Coast 30 ($199, 2 lbs. 6 oz./1.07 kg, regular), with 600-fill down, while heavier and bulkier, is even slightly roomier and has the zippered internal pocket.

The Verdict

With a bit more space than some of the best and lightest ultralight down sleeping bags, while weighing just a few ounces more—and costing less—plus a high warmth-to-weight ratio and packability, the Marmot Hydrogen 30 certainly ranks among the few very best ultralight, 30-degree, mummy bags.


You can support my work on this blog, at no cost to you, by clicking either of these affiliate links to purchase a Marmot Hydrogen 30 at, or a Marmot Lost Coast 30 at

See all reviews of sleeping bags, air mattresses, backpacking gear, and ultralight backpacking gear at The Big Outside, plus my “Pro Tips for Buying Sleeping Bags” and “10 Pro Tips: Staying Warm in a Sleeping Bag.”

And don’t miss my popular reviews of “25 Essential Backpacking Gear Accessories” and “The Best Backpacking Gear” of the year.

NOTE: I tested gear for Backpacker magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See the Gear Reviews page at The Big Outside for categorized menus of all reviews and expert buying tips.

—Michael Lanza

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