Greenmagic 400W (GM400B)
#4 in LargeFull review
A low-cost 400 W folding panel for owners of large power stations who camp by the car or RV. The thin spec sheet means checking a station’s voltage limit before buying.
Amazon $315.99$315.99
The Greenmagic 400W (GM400B) is the better portable solar panel overall, rated 4.3 to 4.0. The Greenmagic 400W (GM400B) leads on durability and features. The DOKIO 300W Foldable Kit costs $136.22 less ($179.77 vs $315.99).
DOKIO 300W Foldable Kit
#12 in LargeFull review
A low-cost all-in-one kit for keeping a 12 V RV, boat or camper battery topped up. Power-station owners are better served by a panel with published electrical specs.
Amazon $179.77$179.77
Prices were last checked October 26, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Greenmagic 400W (GM400B) for durability (IP65 vs no IP rating, 1-year warranty) and features (built-in kickstand, series/parallel vs USB output).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every large portable solar panel; a clear win is highlighted. How we rank explains each one.
| Factor weight | Greenmagic 400W (GM400B) | DOKIO 300W Foldable Kit |
|---|---|---|
| Overall rating | 4.3/5 | 4.0/5 |
| Value 30% | 98 $0.79 per rated watt | 100 $0.60 per rated watt |
| Tested output 20% | 92 not yet tested; estimated 88% of rated watts from the median of the 11 tested panels | 92 not yet tested; estimated 88% of rated watts from the median of the 11 tested panels |
| Portability 15% | 100 18.6 W per lb (21.5 lb (9.8 kg)) | 100 19.7 W per lb (15.2 lb (6.9 kg)) |
| Durability 15% | 36 IP65 | 0 no IP rating, 1-year warranty |
| Efficiency 10% | 75 23.5% claimed efficiency | 50 efficiency not published (neutral score used) |
| Features 10% | 55 built-in kickstand, series/parallel | 20 USB output |
Specifications
| Greenmagic 400W (GM400B) | DOKIO 300W Foldable Kit | |
|---|---|---|
| Output | ||
| Rated power | 400 W | 300 W |
| Tested output | Not tested (estimated 88%) | Not tested (estimated 88%) |
| Efficiency | 23.5% (the listing gives a 21.5-23.5% range without saying cell or module; the top of the range is recorded) | - |
| Cells | Monocrystalline | Monocrystalline |
| Bifacial | No | No |
| Electrical | ||
| Series / parallel | Yes | - |
| Connections | ||
| Output connector | MC4 | - |
| Cables included | - | 9.85 ft (3 m) cable, PWM controller, SAE, XT60 and alligator-clip leads, DC5521, DC5525, DC35135 and DC6440 adapters |
| USB ports | None | Dual USB ports; they charge devices when a 12 V battery is connected |
| Build | ||
| Weight | 21.5 lb (9.8 kg) | 15.2 lb (6.9 kg) |
| Folded size | 32.09 x 31.30 x 1.97 in | 19.3 x 37.4 x 1.1 in |
| Kickstand | Yes | - |
| Water resistance | IP65 | - |
| Warranty | - | 1 years |
| Released | 2025-09 | - |