Selecting the products to include in our reviews is never easy. In the case of 3-season backpacking sleeping bags, we searched for the top-rated hooded bags under 2.5 pounds with temperature ratings between 20-35°F. The Hyperion was an exciting choice because it weighs just over a pound but promises 32° performance. In our tests, however, this temperature rating proved to be largely aspirational. The bag thus didn't score that well in our 3-season review, but it's worth considering alongside other ultralight sleeping bags.
Performance Comparison
The Therm-a-Rest Hyperion is exceptionally light. To fully enjoy this benefit consider using it with a ultralight shelter or no shelter at all.
Warmth
This bag contains premium, 900 fill power, goose down, but only 9.2 ounces of it. With this insulation, it receives a 32°F lower limit EN temperature rating. For comparison, the Western Mountaineering MegaLite has a similar 30° rating but comes with 30% more down (by weight).
The Western Mountaineering MegaLite (left) and Therm-a-Rest Hyperion (right) both have similar quality down, but the MegaLite's extra 4 oz in fill weight bolster the bag's overall loft.
Our testers think the Hyperion feels colder than other bags with a similar rating. Based on this performance we only recommend it for summer or the warmer nights of spring and fall.
Weight
On our scale, the Hyperion weighed in at 1.14 pounds for a size long. This is nearly 5 ounces less than the second lightest bag in the review, the Feathered Friends Merlin. However, comparing the Hyperion's weight with the Merlin isn't really fair. Our testers struggled to stay warm in the Hyperion at 45°F, but felt fine in the Merlin down to 25°F. It's still worth acknowledging the Hyperion's exceptionally low weight, but shoppers should be aware that its warmth-to-weight ratio isn't so exceptional.
Although we think the Hyperion's lower body dimensions are too narrow, we like its ergonomically shaped footbox.
Comfort
To save weight, this bag also features particularly narrow dimensions — dimensions that were narrow enough that some of our testers that sleep on their sides or stomachs consider them a deal breaker. Therm-a-Rest also claims that the fitted length of a size Long is 78 inches (6'6"). Our 6'2" lead tester, however, felt constrained by the hood in a size Long. We thus can't recommend that size for anyone 6'3" or taller.
The Hyperion compresses as well as just about any hooded sleeping bag. It also comes with its own light and effective compression sack.
Packed Size
The Hyperion comes with a great compression sack that's light (1.7oz) and capable of compressing it to its minimum volume. In our test with an after-market compression sack it packed down to 6.6 liters, the smallest in the review. Like its weight performance, however, this packed size is partially a result of its minimal insulation that's unlikely to provide the same warmth as its slightly bulkier competitors.
The half-length zipper only has a single slide. This greatly limits your options for venting excess heat. It could also be a huge problem if the zipper gets misaligned--there isn't any way to back it down and restart it.
Versatility
To achieve its low weight, this bag uses a short, half-length zipper. This zipper also has only one slide, so you're not able to zip the bag up and then use a second slide to vent heat from the bottom of the zipper. Both the shorter zipper and the lack of a second slide limit the bag's ability to excess heat and restrict its use to a narrow range of temperatures. They also prevent you from sharing the bag as a quilt or zipping it together with a second bag.
There are two straps on the underside of the Hyperion for attaching it to a sleeping pad. We really like that they're also removable if you don't want to use them.
Features and Design
Our favorite feature on this bag is its sleeping pad attachment system. If you like to secure your bag to your pad, it will get the job done. If not, it's easy to remove and trim its weight. We also like the simple button closure at the top of the zipper. It's light but effective at preventing the zipper from sliding down if you roll over in the night.
Best Applications
The Hyperion is ideal for ultralight applications when its minimal weight might be worth suffering through the occasional cold night. We envision activities like tentless backpacking or alpine climbing. We don't think it's warm enough, however, for extensive use in spring and fall. In summer though its awesome weight and packed size really shine.
Both the Hyperion (top) and Western Mountaineering MegaLite (bottom) bags that we tested were size long and advertised for heights up to 6'6". This image, however, clearly shows that the Hyperion is several inches shorter.
Value
This is one of the more expensive bags, with a list price of $360. For a bit more, you can get a warmer and more versatile Feathered Friends Merlin. Our Best Ultralight Sleeping Bag Review also includes several other options, like the Editors' Choice Feathered Friends Flicker, that are similarly light and warm but cheaper. For these reasons, we don't consider this bag a great value.
Conclusion
The Hyperion's shockingly low weight and minuscule packed size caught our attention. A single pound for a full 3-season sleeping bag?!? That seemed impossible. Unfortunately, it turns out that it was. Although this bag's down is high-quality, the limited amount of it wasn't able to convince our testers that it can provide adequate warmth for spring or fall. The Hyperion is still a great bag, but shoppers should know that its better suited for summer or ultralight sufferfests.
