The Complete Sleeping Bag Guide for NZ Trampers & Campers

Understanding Temperature Ratings

Temperature ratings are the most misunderstood spec on any sleeping bag. The number on the tag doesn't mean "you'll be warm at this temperature" — it means something more specific, and knowing the difference could save you a very bad night.

The ISO 23537 Standard

Quality sleeping bags are rated using the European ISO 23537 standard, which defines three temperature zones:

• Comfort rating — The temperature at which a cold sleeper (typically a woman) can sleep comfortably in a relaxed position without feeling cold. This is the conservative number. Use it if you run cold.
• Lower Limit (Limit rating) — The temperature at which a warm sleeper (typically a man) can sleep in a curled position without waking cold. Most manufacturers lead with this number.
• Extreme rating — Survival only. A cold sleeper can maintain basic survival at this temperature but will be uncomfortable and at risk of hypothermia. Do not use this as a planning figure.

Which Rating Should You Use?

For tramping in New Zealand, plan around the Comfort rating — not the Limit. Hut temperatures vary wildly. A DOC hut in mid-winter Fiordland may sit only a few degrees above zero inside. Tent camping drops further, especially at altitude. The cost of being too warm is unzipping a zip. The cost of being too cold is a miserable, dangerous night.

A general rule of thumb for NZ tramping: choose a bag rated at least 5°C below the coldest temperature you expect to encounter. Three-season tramping in most of New Zealand suits a bag rated to around -5°C comfort. For alpine or winter use, go colder.

Why Ratings Vary Between Manufacturers

Not every brand uses ISO-certified testing. Some older or budget bags use self-declared ratings that are optimistic at best. When comparing bags, look for ISO-tested ratings and compare like for like — Comfort-to-Comfort, not Comfort-to-Limit.

Down vs Synthetic Insulation — The NZ Context

The insulation inside your sleeping bag determines how it performs when things get wet, how much it weighs, and how it packs. New Zealand's climate — which combines high rainfall, high humidity, and rapid weather changes — makes this choice more nuanced than most.

Down Insulation

Down (goose or duck) offers an unmatched warmth-to-weight ratio. A quality down bag packs small, lasts well with proper care, and feels noticeably lighter in your pack than a synthetic equivalent at the same temperature rating. The traditional limitation — that down loses loft when wet — is now largely addressed by hydrophobic down treatments used by brands like One Planet and Rab. These treatments cause water to bead off the down clusters rather than soaking in, significantly improving performance in damp conditions.

For most NZ tramping and hut use, down is the right call. The weight and pack size savings are meaningful when you're carrying a full pack for multiple days.

Synthetic Insulation

Synthetic bags retain more warmth when wet and dry faster than untreated down. They're also more accessible price-wise at the entry level. The trade-off is weight and pack size — a synthetic bag rated to the same temperature as a down bag will typically be heavier and bulkier. For car camping, where pack weight is irrelevant, this doesn't matter at all. For multi-day tramping, it does.

For a deeper breakdown of both insulation types with specific NZ considerations, read our full article: Down vs Synthetic Sleeping Bags — Which is Right for You?

Fill Power Explained

Fill power is a measure of down quality — specifically, how much space one ounce of down occupies in cubic inches. Higher fill power means the down clusters are larger and trap more air per gram of weight, resulting in a warmer, lighter bag.

Fill Power Ratings at a Glance

• 600–650 fill power — Solid entry-level down. Warmer and more compressible than synthetic, but heavier than high-fill alternatives at the same temperature rating.
• 700–750 fill power — The sweet spot for most trampers. Good warmth-to-weight ratio, reasonable cost.
• 800–850 fill power — Premium territory. Noticeably lighter and more compressible. Suitable for technical tramping and alpine use.
• 900+ fill power — Expedition-grade. The lightest, most compressible option available. Used in bags designed for extreme cold and weight-critical alpine routes.

Fill Power vs Fill Weight

Don't mistake fill power for fill weight. Fill weight is the actual amount of down in the bag. A bag with high fill power but low fill weight might still be under-insulated for cold conditions. Both numbers matter. Manufacturers sometimes list only fill power — if warmth is critical for your trip, check the temperature rating against ISO standards rather than relying on fill power alone.

Fit and Shape — Mummy, Semi-Rectangular, and Quilts

Shape affects warmth efficiency, comfort, and weight. The best shape depends on how you sleep and what you're doing.

Mummy Bags

Mummy bags taper from shoulders to feet, minimising dead air space your body has to heat. This makes them the warmest and most thermally efficient option. Most serious tramping bags are mummy shaped for this reason. The hood cinches around your head for warmth at the neck — critical on cold nights. The trade-off is that some sleepers find them restrictive.

For NZ hut tramping, most serious trampers use mummy bags. When temperatures drop, that thermal efficiency matters.

Semi-Rectangular Bags

Wider at the hips and shoulders, semi-rectangular bags offer more room to move. They're less thermally efficient than mummies but more comfortable for those who shift around in their sleep. Good for milder conditions, car camping, and anyone who finds mummy bags claustrophobic.

Sleeping Quilts

Quilts are an ultralight option that eliminates the insulation beneath you (which is compressed by your body weight and does almost nothing anyway). Used with a sleeping pad for underside insulation, a good quilt can save significant weight over a full mummy bag. The One Planet Quest Pro Quilt is designed for experienced trampers who have their sleep system dialled and want to cut pack weight. Not ideal for beginners or for conditions where temperatures fluctuate unpredictably.

Bag Length and Fit

A bag that's too long has extra dead air space at the foot that your body has to heat — wasteful and cold. A bag that's too short compresses the insulation at your feet. Most manufacturers offer regular and long sizes. If you're over 185cm, check the bag's rated maximum height before buying.

NZ-Specific Considerations

New Zealand's geography creates conditions that don't fit neatly into generic gear guides written for European or North American audiences. Here's what actually matters for tramping and camping in this country.

The West Coast and Fiordland

Wettest places in the country. Fiordland regularly receives over 7,000mm of annual rainfall. Milford Sound averages around 6,000mm. If you're tramping here — Milford Track, Routeburn, Kepler, Dusky — expect extended wet periods. Hydrophobic down or a synthetic bag is worth considering, and a dry bag inside your pack is non-negotiable. Even the best down bag won't save you if it's been sitting in a waterlogged pack for two days.

Alpine Conditions and Shoulder Seasons

New Zealand's alpine environment is notoriously unpredictable. The Southern Alps can deliver snow in any month. Shoulder season tramping (March–May, September–November) in alpine areas requires a bag rated well below zero. Temperatures at altitude on the Main Divide can drop to -10°C or colder at night. Plan for this, not for the average.

DOC Huts

New Zealand's hut network is exceptional — but huts are not hotels. Most DOC huts are unheated or have a single small wood burner. Hut temperatures on cold nights closely track outside ambient temps, especially in drafty older huts. A bag rated for tent camping is equally appropriate for huts. Don't be fooled by the walls — they keep the rain off, not the cold out.

Huts are also shared spaces. Bring earplugs. This is unrelated to your sleeping bag but equally important for a good night's sleep.

Condensation in Tents

Even on dry nights, condensation builds inside tents. A wet sleeping bag loses insulation effectiveness. Down bags with hydrophobic treatment handle this significantly better than untreated down. If you're tent camping regularly, this is a meaningful factor in your insulation choice.

Summer Tramping

Don't underestimate summer nights in the hills. Even in January, a night on the Tararua Range or the Kaimanawa ranges can drop to 5°C or lower at hut level. A bag rated to around -5°C comfort will see you through NZ summers comfortably. Light bags rated to +10°C or +12°C are only appropriate for low-altitude, genuinely warm-weather camping — coastal sites in January, for example.

Sleeping Bag Recommendations by Use Case

Here's how our range maps to real NZ use cases. See the full selection at Dwights sleeping bags.

Weekend and Multi-Day Tramping (Huts and Tents)

This is the core NZ use case — three to seven days on the track, mix of huts and tent camping, weather unpredictable. You need a down bag that's light enough to carry, warm enough to handle cold hut nights, and ideally treated to handle damp conditions.

• One Planet Nitrous ($499–$549) — Our best-seller for good reason. Hydrophobic down, solid temperature rating, excellent warmth-to-weight ratio. The benchmark three-season tramping bag.
• One Planet Sonder ($599–$699) — A step up in warmth and down quality. Suits cooler tramping, shoulder season use, and those who run cold.
• One Planet Cocoon ($699–$749) — The warmest of the One Planet three-season range. Ideal for winter hut trips, the colder South Island tracks, and trampers who want the security of extra warmth.

Alpine and Expedition Use

For mountaineering, ski touring, and routes where overnight temperatures regularly drop below -10°C, you need expedition-rated gear.

• One Planet Bush Lite ($849–$1,019) — High fill power down, designed for serious mountain use. Packs small, performs cold.
• Rab Neutrino Pro ($1,091) — Premium hydrophobic down construction, exceptional warmth-to-weight. One of the best expedition bags on the market for serious alpine use.
• Rab Expedition 1000 — Extreme cold rating for genuinely polar or high-altitude conditions.

Ultralight Tramping

• One Planet Quest Pro Quilt ($449–$479) — For experienced trampers building a gram-counted sleep system. Pairs with a quality sleeping pad. Significant weight saving over a full mummy bag at comparable warmth.

Car Camping

Pack weight doesn't matter. Comfort and value do.

• Dwights Thermoshell -8 ($129.99) — Our own synthetic car camping bag. Rated to -8°C, good size, outstanding value. Heavy and bulky by tramping standards, but that doesn't matter when you're driving to the campsite. Not suitable for hiking or hut trips — keep it in the car or the boot.
• One Planet Sac ($259) — A step up in comfort and packability for car campers who want something a bit more refined.

Kids

• Dwights Kids Thermopod ($119.99) — Sized right for kids, rated for NZ camping conditions. Synthetic insulation that handles the abuse children tend to deliver. Good for campgrounds, beach trips, and introductory hut adventures.

Not sure which bag fits your trip? Browse our full range and read more on our sleeping bag blog for detailed comparisons and advice.

Care and Storage

A sleeping bag is a significant investment. How you care for it determines how well it keeps performing.

Washing

Down bags should be washed in a front-loading machine (no agitator) on a delicate cycle with a down-specific cleaner like Nikwax Down Wash. Never use regular detergent — it strips the natural oils from the down and degrades loft. Rinse thoroughly. Dry on low heat with two or three clean tennis balls to break up clumps. This takes a long time — two to three hours in a commercial dryer. Don't rush it. Damp down can mildew.

Synthetic bags are more forgiving and can be washed with a gentle general detergent. Same low-heat drying process applies.

Drying After a Trip

Hang your bag out and air it thoroughly after every trip — even if it doesn't feel wet. Body moisture accumulates through the night and will degrade insulation over time if the bag is stored damp. Even a few hours on a clothesline after you get home makes a real difference.

Storage

Never store a sleeping bag compressed in its stuff sack. Compression over extended periods permanently damages insulation — both down and synthetic. Store your bag loose: hang it in a wardrobe, store it in a large cotton storage sack, or lay it flat. The stuff sack is for transport only.

Re-Waterproofing Down

Hydrophobic down treatments lose effectiveness over time and with washing. After a few seasons or a wash cycle, apply a down-specific DWR treatment like Nikwax Down Proof to restore water repellency. It's a small step that meaningfully extends performance in NZ's wet conditions.