When you're choosing among charge controllers solar BOS components, the solar combiner box doesn't get as much attention as the inverter, but it decides how many panel strings you can safely combine before they reach the controller. Today's comparison looks at two very different approaches: a compact combiner box priced at $62.54 and a larger, more robust combiner box at $219.99. The $157.45 gap between them is too big to ignore, so let's see what it actually buys you.
Quick verdict
The right combiner box comes down to array size and how much built-in protection you want. If you only need a few inputs, the compact, lower-priced combiner is a solid match. For a larger array with more inputs, the bigger unit delivers more comprehensive protection.
Comparison at a glance
| Feature | 4-String Combiner Box | 6-String Combiner Box |
|---|---|---|
| Price | USD 62.54 | USD 219.99 |
| Price bar | ||
| Input strings | 4 | 6 |
| Circuit breaker | 63A, 550V | 63A breaker + 20A fuses |
| Surge protection | 2 devices, 40KA, 600V | Included surge and short circuit protection |
| Housing | ABS/PC | Metal spray housing |
| Security | Combination lock | Lock and key |
| IP rating | IP65 | IP65 |
| Wiring | Wall-mount plates included | Pre-wired with solar wires |
Where each product wins
The lower-priced combiner is the better fit when you have a modest array and want a lower upfront cost. Its compact footprint works well in tight spaces, and the included hardware helps you get it mounted without extra purchasing.
The higher-priced combiner pulls ahead when you need more input capacity and a more substantial enclosure. It's a ready-to-go box with built-in protections, making it a stronger match for permanent, larger-scale installations.
Product notes
4 String Solar Combiner Box
The 4 String Solar Combiner Box keeps the installation simple. It has a standard 63A circuit breaker rated at 550V, two surge protection devices at 40KA/600V, and an IP65-rated ABS/PC housing that can handle weather exposure. The package includes a combination lock and four mounting plates, so you can fix it to a wall without hunting for extra hardware. For a small array, the main limitation is the four-string input limit: each connected PV string is rated for a maximum input current of 10A, and the total input is capped at 40A. If you plan to expand to five or more strings, this unit will run out of inputs. It's also physically compact, which is good for tight spaces but means you won't have room for a bigger combiner later.
6 String Solar Combiner Box
The 6 String Solar Combiner Box is a more complete solution right out of the box. It comes pre-wired with solar system wires and includes a built-in ground connector, so you spend less time running wire and more time securing connections. The 20A rated fuses give each string individual overload and overcharge protection, and the metal spray housing with lock and key adds another layer of security. The trade-off is that this unit is built for bigger, three-phase installations; if your setup is a small single-array system, you're carrying extra capacity you may not use. It's a heavier, more permanent box that trades simplicity for scalability.
Final choice by use case
For a modest array, choose the lower-priced combiner. It's compact and comes with mounting hardware, so you can get a straightforward install done without a lot of extras.
For a larger installation, choose the larger combiner. It's ready to handle more inputs and a permanent setup, with built-in protections that suit a bigger solar system.
