Reviews You Can Rely On

Kelty Cosmic 0 Review

An inexpensive option that will keep you warm, but too bulky and heavy for heading more than a few miles into the backcountry
Kelty Cosmic 0
  • 1
  • 2
  • 3
  • 4
  • 5
Price:  $300 List | $279.95 at Amazon
Compare prices at 3 resellers
Pros:  Warm, inexpensive
Cons:  Heavy, large packed size, not very weather resistant
Manufacturer:   Kelty
By Matt Bento ⋅ Senior Review Editor  ⋅  Dec 14, 2021
Our Editors independently research, test, and rate the best products. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Learn more
42
OVERALL
SCORE


RANKED
#13 of 13
  • Warmth - 20% 6.0
  • Weight - 20% 2.0
  • Comfort - 20% 6.0
  • Packed Size - 15% 2.0
  • Weather Resistance - 15% 3.0
  • Features - 10% 6.0

Our Verdict

The Kelty Cosmic Down 0 is the heaviest, least weather-resistant bag in our review. A few years ago, this was the best bargain in winter sleeping bags, but the competition has grown fierce recently, and it's no longer our favorite in its price range. You do get a bag that still fulfills the primary job of a cold weather sleeping bag—keep you warm. Despite the low price, the Cosmic Down still has great features like a draft collar and full-length draft tube to shield you from winter winds. While not the most comfortable bag we tested, there is still ample room for side sleepers. It is fine for car camping, but there are warmer, lighter, and more weatherproof bags at this price point that we would rather recommend.

Looking for a three-season bargain?
The Kelty Cosmic 20 is another bargain for a three-season backpacking sleeping bag. For the impressively low price tag, Kelty gets the job done with a reasonably warm, decently comfortable, and semi-lightweight sleeping bag. If you're looking for an affordable all-arounder but don't need the warmth of the Cosmic 0, the Cosmic 20 might be the perfect match.

Compare to Similar Products

 
Kelty Cosmic 0
This Product
Kelty Cosmic 0
Awards  Editors' Choice Award Best Buy Award   
Price $279.95 at Amazon
Compare at 3 sellers
$639.95 at Backcountry
Compare at 2 sellers
$315 List
$315.00 at REI
$299 List$242.03 at Amazon
Compare at 2 sellers
Overall Score Sort Icon
42
73
62
59
55
Star Rating
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
Pros Warm, inexpensiveOne of the warmest bags in the test, lightweight, compression sack includedDWR shell fabric, glow in the dark zipper, large draft tube, inexpensiveDual zipper for venting and sitting up, zippered stash pocket, affordableWeather resistant, comfortable, inexpensive
Cons Heavy, large packed size, not very weather resistantLack of hydrophobic down, missing top hood cinch, snug fit not everyone's favoriteHeavy, static drawstring around the faceHeavy, small draft tube allows cold air infiltration, static drawcord over the faceHeavy, zipper snags
Bottom Line An inexpensive option that will keep you warm, but too bulky and heavy for heading more than a few miles into the backcountryA truly supreme sleeping bag that stands out for impressive weight savings without missing out on warmthAn inexpensive bag that offers excellent warmth and weather resistance, albeit heavier than most in our fleetA great first four-season bag that weighs a little more but costs a bit less than mostThis bag is heavy on the warmth and light on the wallet
Rating Categories Kelty Cosmic 0 Mountain Hardwear P... Mountain Hardwear B... Marmot Never Summer 0 Rab Ascent 900
Warmth (20%)
6.0
8.0
7.0
6.0
5.0
Weight (20%)
2.0
8.0
6.0
6.0
5.0
Comfort (20%)
6.0
6.0
6.0
6.0
6.0
Packed Size (15%)
2.0
8.0
5.0
5.0
4.0
Weather Resistance (15%)
3.0
6.0
7.0
6.0
6.0
Features (10%)
6.0
8.0
6.0
6.0
8.0
Specs Kelty Cosmic 0 Mountain Hardwear P... Mountain Hardwear B... Marmot Never Summer 0 Rab Ascent 900
Measured Weight (lbs, size Regular) 4.56 lbs 2.68 lbs 3.13 lbs 3.19 lbs 3.29 lbs
Fill Weight (oz) 39.5 oz 29.6 oz 35 oz 36.2 oz 31.7 oz
Type of Down Fill Duck Down Goose Down RDS Cert/Fluorine Free Down Down European Goose Down
Fill Power 550 850 650 650 650
Material Weight (excludes down, oz) 39.5 oz 13.28 oz 15.1 oz 14.9 oz 20.98 oz
Temperature Rating 0°F 0°F 0°F 0°F 0°F
Pocket Yes Yes Yes Yes Yes
Shoulder Girth (inches) 62" 58" 62" 62" 59"
Hip Girth (inches) 58" 52" 53" 57" 51"
Foot Girth (inches) Not listed Not listed Not listed 48.5" 49"
Shell Material 20D Nylon 10D nylon Ghost ripstop, DWR finish 20-denier ripstop nylon 20-denier ripstop nylon Pertex Microlite
Continuous Baffle Yes No Yes Yes Yes

Our Analysis and Test Results

Cosmic Down 0 Updates


Kelty has updated their Cosmic line since our test cycle with this winter bag. The new model was revised with trapezoidal baffles, and the water-repellent coating is now PFC-free. The fill weight has increased by 6 oz, so it's a little warmer than the previous iteration. Most importantly, the weight (now over 4.5 pounds for size Regular), packed size, and price have increased significantly. It's now a very large sleeping bag that is unlikely to fit in many backpacking packs. Compare the two versions below; the model we tested is pictured first, followed by the updated Cosmic Down 0.

Click to enlarge
Click to enlarge

We have had our hands on the newer version, though, and can confirm that it's heavier and bulkier than ever. We're linking to the updated version above, but the content of this review from here on refers to that older version.

Hands-On Review of the Cosmic Down 0


There's no getting around it—this bag comes in at the bottom of the heap in nearly every one of our testing metrics. If the high price of premium down feathers is stopping you from enjoying cold weather camping, the Cosmic Down provides the necessary warmth but is a bear to carry around in the backcountry.

This bag is warm, lofty, and affordable, but also quite heavy.
This bag is warm, lofty, and affordable, but also quite heavy.
Credit: Matt Bento

Warmth


With 33 oz of 600 fill power duck down, the Cosmic Down is as warm as the super-lightweight Western Mountaineering Versalite, which costs hundreds of dollars more and is almost two pounds lighter. A draft collar and an effective draft tube help trap in heat, and so does the narrow foot box.

While not as comfortable for tossing and turning or stomach sleeping, a narrow cut reduces the bag's uninsulated space, keeping the user warmer. While this bag's shell fabric compromises weather resistance, and low fill power down adversely affects packability, warmth is one metric where this budget-friendly bag still does ok.

Light?...not exactly, but this bag does bring the warmth at a...
Light?...not exactly, but this bag does bring the warmth at a fraction of the cost of the competition. Not a bad deal for winter car camping.
Credit: Matt Bento

Weight


At 3.8 lbs, the Cosmic 0 is one of the heaviest bags in our review. This is because of the relatively heavy shell materials and the 33 ounces of duck down needed to achieve the same warmth as lighter bags with higher quality down.

While thick and durable, the 50-denier ripstop shell adds lots of weight. The fill weight to material weight ratio on this bag is about 1:1, where on the Western Mountaineering Versalite, it's 3:1. This bag has a relatively poor warmth to weight ratio and wouldn't be our first choice to lug into the mountains, but it's still lighter than many of the synthetic options out there. If you aren't hiking far, this Best Buy on a Tight Budget could be the ticket, especially if you're looking to save some Benjamins.

Comfort


A generous 62" of girth around the shoulders make it possible for back and side sleepers to snuggle in comfortably. The foot box is on the narrow side at 40", which helps maintain heat efficiently, but doesn't allow for much space to spread your feet around.

We feel that staying warm in bitterly cold winter conditions affects our comfort level more than room to spread out. But if you think you'll be spending hundreds of hours inside a sleeping bag this winter, you'll want something more spacious.

Packed Size


The 600 fill down is the least compressible fill material in our selection, but the Cosmic 0 packs down smaller than the warmest bags in our review, which contain more much more down and have roomier cuts.

The included stuff sack is enormous, but our testers managed to cram the Cosmic 0 down to a backpackable size with a compression sack. If you're primarily looking for a sleeping bag for car camping or short backpacking trips, packed size is less of a concern.

This sleeping bag will occupy quite a bit of space in your pack.
This sleeping bag will occupy quite a bit of space in your pack.
Credit: Jenni Snead

Features


The Cosmic 0 offers many features similar to bags two and three times its price. It has a full-length draft tube that hangs down over the zipper and keeps out wind and moisture. When fully zipped, the draft collar rests under the chin, but it doesn't have a cinch-cord. The hood is well insulated and kept our testers' heads toasty.

We feel that deeper hoods are generally more comfortable, as they aren't as claustrophobic feeling and it's easier to cover our faces when it's super cold out completely. The Cosmic 0 has four webbing loops intended to create a way to attach a sleeping bag using cordage (user provided). Our testers had various opinions on this feature.

A stash pocket on the outside of the bag is nice for quick access at...
A stash pocket on the outside of the bag is nice for quick access at night, but not very effective for keeping batteries or phones warm.
Credit: Matt Bento

Some thought that the tie-in points were helpful for staying on the pad all night, others felt they were unnecessary and inhibited them from sitting up in the bag to drink coffee or investigate curious nighttime sounds. Our lead tester accidentally got one of the loops caught in the zipper and almost ripped it off. Overall, we felt that this bag has one of the more "snaggy" zippers in our review selection. The Cosmic does not have a stash pocket, but the stuff sack will do the trick if you need to keep small items like batteries warm and contained inside the bag.

Credit: Matt Bento

Weather Resistance


This bag scored low in this metric because it wetted out through the stitching in our light rain test, and it was the only bag in our review that had this problem. It also absorbed the most water in our submersion test and took the longest to dry. Unlike many of its competitors, this bag doesn't have a DWR treatment on its shell fabric. The good news is that you probably won't be using your 0-degree bag in a rainstorm, and weather resistance is the least of your concerns if your sleeping bag is submerged underwater. You can always add a DWR treatment to your bag after purchase pretty easily (we like Nikwax products for this purpose).

Nonetheless, these tests illustrate that the Cosmic is more vulnerable to melting snow and condensation than the other bags. This problem can be alleviated by an adequate tent or bivy sack.

Without a DWR Treatment or a Goretex membrane, water can seep right...
Without a DWR Treatment or a Goretex membrane, water can seep right through the shell of a sleeping bag.
Credit: Matt Bento

Value


The Cosmic 0 will keep you warm in the low temps for a low price. For folks that only spend a few nights a year in the wintry backcountry, the cash savings are worth the extra weight. For what it is, it's an okay deal.

Conclusion


If you're on a budget and don't want to miss out on some winter adventures because you don't have a warm bag, check out the Kelty Cosmic Down 0. Just make sure you have a good tent or bivy sack if precipitation is in the forecast. For a few short trips a year, the price can't be beat. Though heavy, this bag is plenty warm for sleeping temps down to the single digits, and lack of weather resistance is the main concern here.

Matt Bento
You Might Also Like

Ad-free. Influence-free. Powered by Testing.

GearLab is founded on the principle of honest, objective, reviews. Our experts test thousands of products each year using thoughtful test plans that bring out key performance differences between competing products. And, to assure complete independence, we buy all the products we test ourselves. No cherry-picked units sent by manufacturers. No sponsored content. No ads. Just real, honest, side-by-side testing and comparison.

Learn More