When several solar panel strings need to merge into a single inverter connection, the combiner box is the junction that also handles protection. Two options sit at very different price points: the 2 in 2 Out Solar Combiner Box at USD 125.82 and the 4 String Solar Combiner Box at USD 62.54. Your choice depends on the size of your array, the protection features you want, and how much you plan to spend. The box you choose also needs to match your inverter's input voltage and the way your panels are wired.
Both boxes are listed as new, and the table below shows the key specifications side by side.
Quick verdict
If you're running a modest array and want fuse, breaker, and surge protection in one box, the 2-in-2-out is the cleaner solution. It keeps everything compact. If you're planning a larger array and want more input capacity for less money, the four-string unit is the pragmatic pick.
Comparison table
| Spec | 2 in 2 Out Solar Combiner | 4 String Solar Combiner |
|---|---|---|
| Price | USD 125.82 | USD 62.54 |
| PV inputs | 2 strings | 4 strings |
| Max current per string | 20A | 10A |
| Circuit breaker | 20A DC | 63A, 550V |
| Surge protection | SPD, 40KA, T2 | 2 SPDs, 40KA, 600V |
| System voltage | 500V | 1000V input, 600V output |
| Enclosure material | ABS, PC | ABS, PC |
Where each wins
The 2-in-2-out model takes the lead when per-string current matters and when you want the extra safety of a fuse in addition to the breaker and surge protector. That fuse layer is a meaningful difference, because it catches a fault that could otherwise bypass the breaker. The 4-string model takes the lead when you need more PV inputs, a heavier breaker, higher system voltage, and an IP65 enclosure. It's clearly aimed at installations where the box lives outdoors.
Product notes
2 in 2 Out Solar Combiner Box
This box is about integrating protection. It includes a 20A PV fuse alongside a DC circuit breaker and a Type 2 surge protector, so you get three layers of safety in a single ABS/PC housing. The 11.73-inch square footprint leaves room for wiring, and the included combiner box is all you need to connect two PV strings. The limitation is capacity: it's designed for a modest system, with a 20A breaker and a 500V rating. If your array is small and you value that extra fuse, this is the more protective choice.
4 String Solar Combiner Box
This unit is built for arrays that need more inputs. It combines four PV strings into a single output and includes a 63A, 550V circuit breaker plus two surge protection devices. The IP65-rated enclosure and 1000V maximum input make it suited for outdoor installations, and the package includes a combination lock and mounting plates. The included combination lock also helps deter tampering in an exposed outdoor location. The trade-off is per-string current: each input is rated at 10A, so it suits panels that stay within that limit. If you're expanding from two strings to four, this box saves you from buying a second unit. For a larger solar system, it delivers a lot of input capacity at a lower price.
Final choice
Pick the 2 in 2 Out Solar Combiner Box if you're wiring a smaller array and want fuse, breaker, and surge protection together in a compact housing. Pick the 4 String Solar Combiner Box if you need more PV inputs, a heavier breaker, and higher voltage tolerance, and your per-string current is within its rating. Let the size of your array and the current per string be the deciding factors. The 2-in-2-out is the more protective small-system choice; the 4-string is the higher-capacity choice. The right pick will spare you from reworking the box later.
