Nitecore NU25 UL review

Buy the NU25 UL if you want the lightest rechargeable lamp we cover that still has real reach and a choice of light color. Nitecore publishes 47 grams including the bracket and headband, 400 lumens, 132 meters, 4,351 candela, IP66, and three color temperatures plus red. The figure that will surprise you is the reach: at 10.9 candela per lumen this is the most concentrated headlamp beam on this site, and its 132 m beats the 130 m Nitecore publishes for its own 1,400-lumen NU43. The limit is energy - a 700 mAh cell is 2.6 watt-hours, the smallest store of any rechargeable lamp here.

We have not tested this headlamp. We own none of the products on this site, we have no laboratory, and nothing here is an impression of how it feels on a head after six hours. This review takes every figure Nitecore publishes, runs the arithmetic those figures allow, and says what they do and do not commit the company to.

It also settles an argument this site has been having with itself. Until today we wrote, in four separate places, that the NU25 UL's reputation as the ultralight default was "doing work the published data does not" - because we had recorded its weight, beam distance, candela, runtime and ingress rating as unpublished. All five are published, and have been, on Nitecore's own product page. This is the third Nitecore page we have found by reading nitecore.com/sitemap.xml after guessing a URL wrongly, following the P30i and the NU43. Every page that called the weight unavailable has been corrected in the same change as this one.

The published specification

Sixteen published figures and three gaps. The notable absence is CRI, on a lamp whose headline feature is a choice of three color temperatures - more on that below.

The surprise: this is the longest-reaching headlamp we cover

Nitecore publishes both a beam distance and a peak intensity here, which means the two figures check each other. Under ANSI FL 1 beam distance is the point where illuminance falls to 0.25 lux, so the relationship is fixed and exact.

Put that next to the rest of Nitecore's own range and it produces the most useful single fact on this page. This 400-lumen lamp publishes 132 meters. Nitecore's 1,400-lumen NU43 publishes 130. Three and a half times the output, two meters less reach - from the same company, in the same catalog. If you have ever wondered whether lumens buy distance, that pair answers it more cleanly than anything else we have found.

What it means in use is that the NU25 UL is the unusual ultralight lamp that can actually pick something out at a distance. What it gives up is spill: a beam that concentrated puts proportionally less light at your feet and in the verges, which is the trade throw versus flood sets out. For a lamp you walk by, the NU43's wide 2.7 is arguably the better shape; for spotting a cairn or a trail marker, this one is.

The weight question, finally answered

47 grams, bracket and headband included. That phrasing matters, and Nitecore deserves credit for it: most makers publish a weight without saying what is on the scale, so the figures across a category are not strictly comparable.

So on the raw numbers the NU25 UL is third, within 4 grams of the lightest - and it is the only one of the three whose maker tells you the headband is on the scale. We are not going to re-rank the table on an assumption about what the other two figures cover; we are going to point out that the NU25 UL's reputation for being the lightest practical rechargeable is now defensible from a published figure rather than from forum consensus, which is all we previously had.

Three color temperatures, and the figure that is missing

The feature this lamp is actually sold on is its dual-core MCT emitter: 3,000 K warm, 4,500 K neutral and 6,500 K cool white, plus auxiliary red with two brightness options. Nothing else we cover offers three white color temperatures in one lamp; the Fenix HL18R-T offers two.

Why it matters outdoors is scattering. Cool white at 6,500 K scatters hardest off fog, dust and falling snow, which is why a bright cool beam can be worse than a dimmer warm one in bad air. Warm light at 3,000 K cuts through it and renders browns and reds more naturally, which helps on a trail or a map. Our CRI explained guide covers how color temperature and color rendering differ - they are routinely confused, and they are not the same thing.

Which is exactly where the gap bites. Nitecore publishes no CRI figure for any of the three temperatures. Color temperature tells you the tint of the light; CRI tells you whether colors under it look like themselves. A lamp sold on light quality that publishes the first and not the second is answering half the question. Only two products on this site publish a CRI figure at all - the Acebeam Pokelit AA at 90-plus and the Wurkkos FC11C at 90 - so this is a category failing rather than a Nitecore one, but on this particular lamp it is the figure we would most want.

Two point six watt-hours is the real constraint

Nitecore publishes the cell capacity, which lets the lamp be placed on the measure this site uses across the whole category: stored energy against the weight you carry.

This is the honest counterweight to everything good above. An ultralight lamp is light because it carries less energy, not because it is more efficient, and 2.6 watt-hours is a genuine limit on how long 400 lumens can last. If you want both light weight and endurance, the comparison to make is against the NU43, which carries nearly five times the energy for 69 grams more.

Forty-five hours, and what it does not tell you

Nitecore publishes one runtime figure: a 45-hour maximum. There are four brightness levels, three special modes and two red brightness options, and the 45 hours is not attached to any of them. That is a thinner disclosure than the NU43 manages, where Nitecore at least names 8 lumens and 100 lumens as two separate points.

How runtime is defined sets out the ANSI FL 1 rule these figures are measured under - time until output falls to a tenth of where it started - which is a second reason the single headline number is not a working figure.

IP66: the one place the sheet goes backwards

Nitecore publishes IP66 and a 1 m impact rating. Under IEC 60529 the first 6 is dust tight and the second is protection against powerful water jets - not immersion. That is a real step down from the IP68 Nitecore publishes for the NU43 and Fenix publishes for the HM65R-T, both of which state submersion to 2 meters.

For walking, backpacking and camping in rain, IP66 is enough; dropped in a creek, it is not a rating that covers you. It is better than the IPX4 Petzl publishes across the Tikkina, Tikka and Actik Core, because the dust digit is real and jets are a harder test than splashing. But if the lamp is going near water, the Princeton Tec Vizz publishes IPX7 immersion on replaceable AAA cells and the Black Diamond Spot 400-R publishes IP67.

Small details that are published and worth knowing

• Two buttons, deliberately different in shape and feel, which Nitecore states is for one-handed operation. On a lamp you adjust with gloves on in the dark, that is a design decision rather than a specification, and it is the right one.
• A diffusing stuff sack in the box. Pull it over the lamp and you have a small lantern - a genuinely useful inclusion on a lamp this size, and the kind of thing most makers charge extra for.
• A USB-C to USB-C cable, not USB-A to C. Worth knowing if everything else you carry still charges from an A port.
• Power indicators for remaining charge, which matters on a sealed 700 mAh cell where running out is the whole failure mode.
• No charge-cycle figure. On a built-in battery that is the gap we would most like filled - Petzl states three years or 300 cycles for the Swift LT.

Who should buy something else

Skip it if you need a night's light rather than a night's weight. 2.6 watt-hours is the smallest store here. The Nitecore NU43 carries 12.6 Wh at 116 g, and the Fenix HM65R-T 12.2 Wh with a replaceable 18650 and a CR123A fallback.

Skip it if the lamp will be immersed. IP66 covers jets, not submersion. The Vizz publishes IPX7 and the Spot 400-R IP67.

Skip it if you want a runtime you can plan with. One figure for nine settings, with no level attached, is the thinnest runtime disclosure of any lamp we have reviewed - and the arithmetic says it belongs to the dimmest setting.

Skip it if the battery has to outlive the lamp. The cell is sealed and no cycle life is published. The Petzl Tikka and Tikkina run on three AAA cells you can buy anywhere, which is also the right answer for a car or a drawer.

The verdict, stated as what it commits to

Nitecore commits to 400 lumens, 132 meters, 4,351 candela, three color temperatures plus red, 47 grams with the bracket and headband, a 700 mAh cell, a 45-hour maximum, IP66 and a 1 m drop rating - and the two beam figures agree to within a tenth of a percent, which is as good as disclosure gets. For backpacking, fastpacking or anything where grams are the budget and you still want to see something at distance, this is the lamp, and its reputation is now backed by the maker's own numbers rather than by consensus.

What it does not commit to is a CRI figure on a lamp sold on light color, a runtime attached to any particular level, or a cycle life on a sealed cell - and 2.6 watt-hours is a hard ceiling no interface design gets around. Buy it for weight, reach and color choice. Buy something else if you need endurance, immersion, or a battery you can replace. For the category ranked on what each maker actually prints, see headlamp brands compared.