What is a solar combiner box and do you need one?


One challenge you’ll come across when putting together a solar power system is how to link up all your photovoltaic (PV) modules – i.e. the components that turn light into electricity – without getting tangled in a complex mess of wires.

If you’re using a lot of PV arrays to generate enough solar electricity for your home or small business, feeding all those separate cables into your central load center gets hard to manage, and potentially dangerous.

This is where your solar combiner box, or PV combiner box, comes in.

A solar panel combiner box combines the outputs of all your inverters, or your strings. These feed into the box, turning the electricity into a single circuit. Out of that box comes a single wire you can connect to your main load center.

If that sounds like a handy fix for you, read on. In this post, we’ll dive into the technical and practical aspects of using a PV combiner box, including exactly what they are, how they work, and the benefits you’ll get from using a combiner box for solar panels.

Table of Contents

What is a solar combiner box?

As the name suggests, a combiner box is where different wires and connections are combined. DC Combiner boxes are usually used for large, centralized PV installations, while you’re more likely to see an AC combiner box in residential settings.

At the most basic level, the PV combiner box should contain:

  • An internal load centeror panelboard. This houses overcurrent protection devices, like fuses, and all the busses/busbars (mechanical conductors) or other connections that relay power to these devices and their circuits. In very simple terms, the load center handles incoming power from multiple sources and outputs this into a single circuit.
  • Circuit breakers. These protect the circuits feeding into the box from electrical faults, in case there is a voltage surge.
  • Communication device. Some manufacturersalso integrate a communication device into the combiner box. This means you don’t need a separate communication module to monitor what’s happening inside the system. More on that later in this blog post.

But this really is the bare minimum. A good solar combiner box will form the central hub of your solar energy installation. It’s where you manage power distribution, electricity metering, and communication for the whole system.

That might include PV monitoring and transformers for grid and production metering. It could even offer data transfer to the Cloud, allowing you to keep an eye on the smooth running of the system and catch any problems as soon as they arise.

But more on that later in this post.

Another important thing to note:

AC Combiner boxes are widely used in microinverter systems. That’s because, in these kinds of systems, you would have multiple microinverters or microinverter circuits.

You can read more about the pros and cons of using microinverters vs. string inverters here. Overall, microinverters are usually more reliable and efficient than string inverters.

In this blog post, we’ll focus on AC combiner boxes – which means we’re assuming you’re using a microinverter in your solar system.

Four reasons to use a combiner box for solar panels

Using a top-notch solar combiner box offers far more benefits than simply tidying up your system, or even making your wiring safer. Here are four compelling reasons why:

  1. Save time with a one-time installation
    If the PV system is for your home, the combiner box usually lets you integrate connection and communication functionalities. This means that, once you have the box, you don’t need to install a separate communication gateway. Technicians only need to make one trip to get everything set up.
  2. Easy outdoor maintenance
    With a combiner box, any maintenance on the system can be done outdoors. This is convenient for both you and your installer, as installers won’t need to wait for access to your home to get to work.
  3. You don’t have to make changes to your main load center
    If your PV system uses several microinverter circuit branches, chances are you don’t have enough space on your main load center to connect all those wires. With a combiner box, you don’t need to worry about this – and you won’t have to make the load center bigger to accommodate all of your wiring. You can wire all the branches into the same place – the combiner box – and then install this on the load center.
  4. You avoid electrical faults

Every circuit breaker in the combiner box provides overcurrent protection. If there’s an abnormality on any given circuit branch, the corresponding breaker will trip to protect the system. This gives you more uptime and fewer problems to fix.


The Hoymiles Solar Combiner Box

We mentioned before that the best types of solar panel combiner box offer comprehensive system monitoring and communication.

This is precisely what the Hoymiles Combiner Box offers.

The box has the capacity to group all the microinverter circuits on your system and output this power to your main load center. But more than that, it’s a central hub for your solar energy system, not just a simple tool for combining circuits.  

Hoymiles Combiner Box Diagram
How the Hoymiles PV Combiner Box connects to your microinverters, main load center and grid, and the S-Miles Cloud.
The Hoymiles PV Combiner Box contains:
  • A communication module, with a pre-installed data transmission unit (DTU) for communication, and a meter for measuring power.
  • Solid-core PV current transformers. These are used for production metering.
  • Split-core grid current transformers.These are used for grid metering.
  • Reliable cloud connectivity.The Hoymiles combiner box connects to S-Miles Cloud – our real-time app that monitors the performance of your solar system – through 4G and Ethernet. The DTU collects the PV and microinverter data and sends this to the S-Miled Cloud monitoring platform. This gives you seamless communication and data transfer, so you can keep an eye on the system at all times.

Key Features and Benefits of the Hoymiles Combiner Box

Still unsure? Below we talk you through the features of our own solar combiner boxes, so you can see exactly why each one matters, and how it translates into benefits for you.

Benefits of Hoymiles Solar Combiner Boxes

Hoymiles Combiner Box Benefits

Hoymiles solar combiner box is only available in North America. Please drop us a message for any product inquiry.