Rab Solar Ultra 2 Sleeping Bag review: Bags of warmth and robustness for an amazing price

The Rab Solar Ultra 2 Sleeping Bag is a synthetic mummy bag that’s strong on environmental credentials, as it features recycled fabrics and insulation too. The latter is synthetic, which will still trap warmth and keep you warm when wet, unlike down. It's aimed at lightweight mountain ascents in three-season conditions.

Due to its many excellent qualities, we placed this sleeping bag right at the top of our best sleeping bags roundup. However, if you're after lighter, you'd better head over to T3's best lightweight sleeping bags guide, as that has other, less heavy Rab sleeping bag options. Read my full Rab Solar Ultra 2 Sleeping Bag review below to find out more about this premium camping accessory.

Rab Solar Ultra 2 sleeping bag review: design and build 

When I tested another new 2022 Rab bag for my Rab Neutrino 400 Sleeping Bag review, that model it scored excellently on being lightweight and warm, but the devil's advocate could easily point out that down is unreliable in damp conditions, and lightweight fabrics tend to be more fragile than heavier-weight ones. Almost as if Rab was responding specifically to that point, the Rab Solar Ultra 2 Sleeping Bag is a robust, synthetic sleeping bag that offers the complete counterpoint, but incorporating many of the new design features that make the Neutrino a great sleeping bag. 

First up, the Rab Solar Ultra 2 Sleeping Bag is a mummy sleeping bag with an outer of 100% recycled polyester – 20D Atmos recycled nylon ripstop fabric (38gsm) with fluorocarbon-free DWR, to be specific. Inside we have a triple layer of Recycled Stratus Synthetic Sheet Insulation, 140gsm in the upper and a lower 60gsm in the base. This ensures the sleepers' warmth is trapped efficiently, and the lower section, which is being compressed anyway, is downgraded to save weight and bulk. The former comes in at a reasonable 1140g in regular length, the latter 40 x 22cm – not tiny, but reasonably portable.  

 A key technology here is the excitingly-monikered Thermo Ionic Lining Technology (TILT), a cutting-edge trick stolen from Rab’s premium super-lightweight Mythic Ultra bag. The basic premise is to reflect heat back into the bag more efficiently by adding a metallic reflective layer to the liner face. This not only boosts warmth (by up to 15%, according to Rab), but also adds very little weight, a handy combination in the world of sleeping bags.  

A less technical but ingenious trick is the combined use of offset localised quilting and elasticated internal quilting to pull insulation into the sleeper, reducing cold spots. Elsewhere there’s a neck baffle designed to trap heat, along with a 3/4 length main zip and YKK Anti-snag zip insert and anti snag internal zip guard – just like on the Rab Neutrino 400 Sleeping Bag.  

Rab Solar Ultra 2 Sleeping Bag review: performance and comfort 

Slightly confusingly, Rab’s sleep limit for the Rab Solar Ultra 2 Sleeping Bag is a robust -10°C (15°F), but the ISO EN much less generous, with a comfort level at 2°C (36°F), and a limit of -4°C (25°F). Either way, even Rab doesn’t claim anything more than three seasons, which I’d agree with in general. This is a tiny bit of a shame, as the best seasons for synthetic bags are the wetter, colder months, where days are short and the likelihood of things getting very wet is far higher than in the summer heatwave days. (Check out T3's down vs synthetic sleeping bag explainer for more info on that.)

Although the outer is made from entirely recycled material, it’s entirely not apparent in use, the slick but soft material being as comfortable as any other good sleeping bag on the market. Indeed, at the £200 price point the Rab Solar Ultra 2 Sleeping Bag feels like a premium bag in every sense. The attention to detail is identical to the Rab Neutrino 400 Sleeping Bag, which is nearly double the price. There are reasons for that of course, but the point is that the Solar Ultra 2 has a top quality look, feel and finish. The mobile phone or battery pocket is a good size, the adjustable hood and neck baffle easy to tweak for maximum comfort or warmth, and the insulation lofts to give a comfortable nest.  

The one issue that synthetic bags (and jackets) can suffer from is the insulation becoming compressed over time, something that’s difficult to counteract. In other good news, the zip anti-snag works perfectly, a major plus of this new generation of Rab bags. It’s simple enough – two stiffened areas either side of the zip combined with a plastic spreader – but it saves so much faffing around it’s really a tiny revelation.  

 Rab Solar Ultra 2 Sleeping Bag Review: verdict 

It’s hard not to like the Rab Solar Ultra 2 Sleeping Bag – the quality is excellent, and the materials are recycled, ticking the all-important sustainability box. The price is very reasonable, bearing this in mind too, and the robustness and wet-weather tolerance will be crucial for a wide range of folk, especially anyone from the UK.

It’s a shame the temperature rating isn’t a touch lower, which would make this bag an excellent year-round, all-conditions candidate, but in terms of bang for your buck, there’s an awful lot here for relatively little cash. At 1.1kg-odd, it’s no featherweight, but very few synthetic bags are, and the pack size – thanks to a well-designed compression sack – is decent too. Overall, if you’re looking for a robust, three-season bag at a wallet-friendly RRP, this is more than worth a look.