A Gen'24 foldable panel, four SunPower cells
The Xtorm SolarBooster 28W belongs to what the brand itself labels its "Gen'24" range. It is a foldable, portable solar panel with no built-in battery, designed to charge a phone, tablet, GoPro or power bank straight from the sun. It unfolds into four panels, each fitted with one monocrystalline SunPower cell, for a combined rated output of 28W.
Unfolded, it measures roughly 88.7 x 23.6cm at 2.3cm thick. Two USB ports (one USB-A, one USB-C) allow two devices to charge at once, and a built-in LCD screen shows the amperage being delivered live. With no internal battery, this panel stores nothing: a device, or a power bank, needs to stay plugged in while the panel sits in the sun for the energy to actually transfer.
UK pricing, around £120 to £130 depending on retailer, places it well above foldable USB panels of comparable power already reviewed on this site, which is worth weighing before deciding.
Efficiency that is never given a number
Xtorm's documentation highlights the cell technology (monocrystalline silicon, ETFE construction, SunPower branding) and claims better efficiency than standard polycrystalline panels, but never publishes an actual efficiency percentage for this model. That is a real gap next to the BigBlue 28W, whose own spec sheet states 24% cell efficiency outright.
No independent measurement exists for this specific model, which is true of nearly every small foldable panel in this category. On panels of comparable rated output, real-world production in full sun typically falls short of the nameplate figure, and drops sharply under cloud cover or at a shallow angle to the sun, regardless of brand.
In practice, this panel behaves like almost every small USB panel in its class: output depends heavily on direct sunlight, useful as a top-up over several hours, but no match for a mains socket for a quick charge.
910g: the heaviest in its own comparison
Folded, the SolarBooster 28W weighs 910g and packs into its supplied carry case. That is a reasonable weight for a panel of this output, but it is also, quite precisely, the heaviest of the four panels Xtorm itself chooses to cite in its own product comparison.
The comparison is particularly unflattering against the BigBlue 28W: at exactly matching rated output (28W), the gap reaches 230g, or 34% more on the scale. Even the Elfcam 40W, despite offering 12W more, is lighter according to figures Xtorm itself publishes in its own comparison table.
The unfolded footprint (88.7 x 23.6cm, 2.3cm thick) stays compact and fits the supplied backpack-style case. But on a product whose central selling point is portability, that extra half-pound compared with the closest rival matters to the decision.
IPX4: protected against water, silent on dust
The SolarBooster 28W is rated IPX4: it resists splashing water and light rain for short periods, but the "X" in place of the first digit means no dust or solid-particle protection is claimed for this product at all. That is not the same as zero dust protection, but it is a figure the manufacturer simply does not disclose.
| Product | Xtorm SolarBooster 28W | BigBlue 28W | Elfcam 40W | FlexSolar 25W pocket |
|---|---|---|---|---|
| Claimed rating | IPX4 | IP44 | IPX5 | Splash-resistant (rating unspecified) |
| Dust protection claimed | Not stated | Yes (level 4) | Not stated | Not stated |
On this specific point, the SolarBooster 28W is the only one of the four cited panels with no dust protection claim whatsoever: the BigBlue 28W (IP44) covers both aspects, and the Elfcam 40W claims a higher rating on water alone (IPX5). None of these ratings has been independently verified in public to date; they are all manufacturer-stated figures.
For everyday hiking or van-life use, this nuance stays secondary as long as the panel is not left out in heavy rain or set down on very dusty ground for hours on end. It is still worth knowing before buying rather than discovering afterwards.
The LCD screen and kickstand: the real differentiator
This is where the SolarBooster 28W genuinely scores. Its built-in LCD screen shows the live amperage being delivered by the panel, which allows for precise adjustment towards the sun to optimise collection, rather than guessing whether the chosen angle is right. Xtorm itself states, in its own comparison table, that none of the three panels it compares itself against (BigBlue 28W, Elfcam 40W, FlexSolar 25W) offer this feature.
On raw connectivity, both ports (USB-A and USB-C) cap at 15W each (5V/3A), a figure that exactly matches the BigBlue 28W at identical panel rated output (28W). Neither offers a DC or MC4 output: this panel cannot plug directly into a power station fitted with a dedicated solar input, a limit shared by almost every USB panel in this format.
The real gap is elsewhere: the BigBlue 28W offers three ports in total (2x USB-C and 1x USB-A) against two on the SolarBooster. For anyone routinely charging more than two devices at once, that is a genuine practical difference. The SolarBooster partly makes up for it with its built-in kickstand, which allows it to sit at the best angle to the sun without an improvised prop, and its carabiner, handy for clipping to a backpack on the move: two ergonomic touches the BigBlue 28W does not offer.
Against the BigBlue 28W: same power, very different price
At exactly matching rated output (28W), the BigBlue 28W is the SolarBooster's most direct rival, and it is also a product already reviewed on this site. The comparison, criterion by criterion, is fairly one-sided on several objective points.
| Criterion | Xtorm SolarBooster 28W | BigBlue 28W |
|---|---|---|
| Rated power output | 28W | 28W |
| Claimed cell efficiency | Not stated | 24% |
| Folded weight | 910g | 680g |
| Output ports | 2 (USB-A, USB-C, 15W each) | 3 (2x USB-C, 1x USB-A, 15W each) |
| Control screen | LCD (amperage) | None |
| Built-in kickstand and carabiner | Yes | No |
| Claimed weatherproofing | IPX4 | IP44 |
| Claimed warranty | 2 years (3 years under 2+1) | 2 years |
| UK price observed | ≈ £120 to £130 | ≈ £60 |
The BigBlue 28W wins on weight, claimed weatherproofing, port count and price. The SolarBooster answers with a genuine LCD screen and ergonomic extras (kickstand, carabiner) the BigBlue lacks, plus a year's extra warranty under its 2+1 scheme. Even so, the observed price gap, more than double, is wide against what those two advantages actually amount to in daily use.
A solar top-up, not a standalone power source
Like any battery-free foldable panel of this output, the SolarBooster 28W earns its keep as a top-up, not as a primary power source. With no internal storage, the energy produced has to be used immediately by whatever is plugged in, or by a power bank sitting alongside: the moment the sun goes or the panel is unplugged, output stops dead.
The hinges between the four folding panels are fairly stiff, with the end panels tending to fold back on their own unless something holds them flat once the panel is laid out on the ground. That is not a dealbreaker, but it is worth knowing: weighing down the corners with stones or the supplied straps avoids the issue entirely.
Used on a multi-day hike, in a van or while camping, this type of panel mainly keeps a phone or power bank topped up over several days with no mains access, rather than delivering a fast charge with full self-sufficiency. The SolarBooster's LCD screen helps precisely with that top-up use, by making it easy to find the best available angle to the sun.
Who the SolarBooster 28W is for
Supplied with a USB-A cable and a USB-C cable, the Xtorm SolarBooster 28W suits travellers, hikers and van-lifers who genuinely value the LCD readout and the ergonomic extras (kickstand, carabiner), and who are willing to pay significantly more for those two additions.
For anyone chasing the best balance between price and available power, with no need for a live amp readout, the BigBlue 28W covers the same outdoor USB charging need at a noticeably lower price, with one extra port and 230g less to carry. For anyone needing more raw power, the Elfcam 40W, cited by Xtorm itself, offers 12W more for a price close to the BigBlue's.
The SolarBooster 28W remains a defensible choice for a specific type of buyer, one who values visual charge feedback and the standing of an established outdoor-accessories brand, rather than an obvious pick for most nomadic solar charging needs.
