A solar combiner box is worth the investment, even if you have a small three-string setup. It protects your solar power system and makes maintenance hassle-free. In addition, the correct combiner box saves you from spending more on your solar setup down the road. The best solar combiner box is reliable, efficient, and not too heavy on your pocket. With this in mind, we compiled a list of the best combiner boxes in the market.
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Best Solar Combiner Box in 2021 at a Glance
- Best Overall: ECO-WORTHY 6 Strings PV Combiner Joint Box
- Second Best Overall: PolyEnergy PV Combiner Box 4 String
- Best for Many Solar Panels: Midnite Solar Mnpv12 PV Array Combiner Box
- Most Compact: Eco-Worthy 4 String Combiner Box
- Most Durable: Midnite Solar Combiner Box Mnpv6-250
- Best Enclosure: AIMS POWER Com3in60A Combiner Box
- Best Budget Combiner Box: ECO LLC 4 Strings PV Combiner Box
- Easiest to Install: ENZPOWER IP66 Combiner Box
Combiner boxes are not just devices that combine the output of strings for an inverter. The best combiner boxes come with specifications that include lightning protection, reverse-current prevention, and disconnect switches—not forgetting that there are some factors to consider when selecting a combiner box. We reviewed each product’s safety capabilities, enclosure, weather resistance, scalability, and much more.
So even if you’re not a first-time buyer, here are the best solar combiner boxes that you should look into in 2021.
The 8 Best Solar Combiner Box in 2021
1. ECO-WORTHY 6 String PV Combiner Joint Box
The Eco-Worthy 6 String PV Combiner Joint Box tops our list for several reasons. To begin with, it has a robust and non-conductive enclosure box. Second, when you open it up, you will find a well-organized internal system. Finally, the build quality coupled with finishing is also impressive.
A single PV lead will get you an input of 10A, which is duty-rated 250 Vdc. That, along with 63A output circuit breakers and ground wires, makes this combiner box very efficient and safe.
The high-current, touch-safe breakers are not the only way this combiner keeps the solar setup safe. Its anti-backflow and anti-reverse protection prevent damage to the wiring. One stand-out feature is the lightning protection, which makes it perfect for an off-grid system. It also holds up pretty well in humidity and high temperatures. Setup is pretty straightforward, and almost anyone can get it done.
This combiner box has many merits, but it falls short in some areas. For example, you can’t use this combiner box for more than six strings. But a solution for that is buying two of these combiner boxes. They are not too expensive and fall in the lower-intermediate price range. Also, we think the wiring should have been thicker. Finally, the lock mechanism is not up to the mark found in other products in the same category.
- Easy to set up.
- High-voltage fuse.
- Over-voltage, short circuit, and lightning protection.
- Tolerance to high temperature.
- Perfect for an off-grid system.
- Relatively small container, one has to, sometimes, get creative with the wire arrangement.
- The locking mechanism needs improvement.
2. PolyEnergy PV Combiner Box 4 String
The PolyEnergy PV Combiner Box 4 String makes our list because of its high-end protection measures. The combiner box comes with 63A output circuit breakers and a 15A output fuse. You will also find a state-of-the-art PV system with a dedicated DC fuse and reverse-current protection, and features make it resistant to short circuit faults.
A high-voltage lightning arrester and waterproof enclosure make this combiner box the perfect solution for areas with a lot of thunderstorms and rain.
The combiner box comes with a mounting buckle, which makes its placement sturdy. It works on both on-grid and off-grid systems. We tested PV and RV solar power, and the combiner box adapts to both as the manufacturer promised.
We think a shortcoming of this combiner box is that it only connects four strings. But if you have a small setup, this is not a problem for you.
- Easy to install with a mounting buckle.
- Lightning and reverse current protection.
- Short circuit and over-voltage protection.
- Waterproof enclosure.
- Works with the both PV array and RV solar power.
- 63A output breakers and DC fuses.
- Connects only four strings.
3. Midnite Solar Mnpv12 Combiner Box
The Midnite Solar Mnpv12 is the go-to if you require a combiner box that supports heavy-duty setups. Unlike other boxes, it supports up to 12 circuit breakers with high output, making it suitable for large buildings and houses.
Another feature that makes it ideal for a large power system is that it supports up to 10 strings with positive fuses. We also found it impressive that the combiner box uses plus bus bars to set up two inverters or controllers. It has 15 position ground bus bars and 15 negative bus bars as well.
We tried the three configurations that the manufacturer suggests, and they all worked without a problem. So you can use it with one grounded, one ungrounded, or two grounded inverters.
The only drawback of this combiner box is that you need to buy breakers and fuse holders separately. It would have been more convenient for customers if they both were included in the combiner box.
- Lightweight and compact.
- Waterproof and corrosion-resistant.
- Plus, bus bars make configuration easy.
- Three different configurations.
- Supports 12 circuit breakers with high output.
- Breakers and fuse holders don’t come with the package.
4. Eco-Worthy PV Solar Combiner Box
If you want an excellent combiner box that does not take up much space, the Eco-Worthy 4 String Solar Combiner Box is your best bet, especially if space is of the essence.
This best solar combiner box comprises three safety measures built into this combiner box, and we tested them out. First, the high-voltage DC fuse, breakers, and ground cables prevent short circuits. Second, the combiner box can manage the overflow of current and voltage to protect the energy system.
The combiner box also optimizes the connection of the PV array to the inverter to keep the setup safe. Like other combiner boxes in its class, it comes with lightning protection and others to protect it from torrents.
At just 4.4 pounds, you can fix the compact enclosure box anywhere. It also has a lighting system to make checking and repairing easy. We also found out that it doesn’t heat up quickly and is tolerant to high humidity.
Where this combiner box falls short is that it only connects four strings. That makes it ideal for a small setup but not large houses and buildings.
- Anti-backflow and lightning protection.
- Prevents short circuits and overflow of current.
- An efficient circuit breaker with high output.
- Lightweight and compact.
- Works in high temperature and humidity.
- High duty rate (250 Volts DC).
- High-voltage fuses.
- Connects only four strings.
- It does not handle a high amperage.
5. Midnite Solar Combiner Box Mnpv6-250
The Midnite Solar Combiner Box Mnpv6-250 is the best option for people who want a durable yet compact combiner box. It weighs 4.4 pounds which makes it easy to install and relocate. In addition, its aluminum box and plastic interior make it corrosion-resistant and rain-proof.
We tried two inverters and chargers on this combiner box. It supports them easily. However, it will not support more than 300 Vdc. The combiner box has inputs for three breakers. But they’re not included in the package and are sold separately by Midnite.
- Lightweight and compact
- Easy to install and relocate
- Waterproof and corrosion-resistant
- Supports two different chargers and inverters
- Breakers are not included in the package
- It does not support more than 300 Vdc
6. AIMS POWER Com3in60A Solar Panels Combiner Box
The AIMS POWER Com3in60A Solar Panels Combiner Box has a well-organized enclosure with flexible mounting options. This allows you to set it up on almost any surface. Furthermore, high temperature and humidity are not a problem for this combiner box as the manufacturer used a rigid casing that ensures the internal components remain protected.
By assessing its performance, this combiner box sports a 1000 Vdc input and output current of 60A. In addition, the 125A output breaker helps minimize the risk of unexpected short circuits. Finally, the package includes replaceable fuses.
The Aims power combiner box offers much that you may not find in your regular box. For one, it is a standalone PV system. This means you don’t need to buy extra equipment like breakers, branch connectors, and disconnect switches. Instead, installation is made easy by a helpful user manual.
As found in most combiner boxes, it comes with lightning and ground protection. It’s waterproof as well, so you don’t have to worry about thunderstorms. Another feature that we do not see much is a tamper-proof lock. This combiner box has that along with a ten-year warranty.
A drawback of this combiner box is that it’s heavy at 15 pounds. That makes it difficult to carry around and relocate.
- Waterproof enclosure with flexible mounting options
- Tamper-proof lock
- Suitable for a high-capacity system
- Over-voltage, short circuit, and lightning protection
- Simple installation
- 125A output breaker
- Perfect for an off-grid system
- No need to buy disconnect switches, breakers, and connectors
- The combiner box is heavy
- It may be tricky to relocate
7. ECO LLC 4 String PV Combiner Box
The ECO LLC 4 String PV Combiner Box is one of the most popular combiner boxes in the US, and it earned its place not only because it’s budget-friendly but because it effectively gets the job done.
The Eco team prioritizes you staying safe as the first thing you notice is the safety labels the combiner box comes with. In addition, it has anti-backflow diodes to prevent damage by surges, short circuits, and reverse current. Finally, the single-input photovoltaic array also protects against overcharge and overload.
The package comes with touch-safe breakers and output cable glands. In addition, it has a lightning protection module and a non-conductive enclosure box, which makes it safer. Another valuable piece of equipment we found in the package was the grounding bus bar. That, along with high voltage breakers, makes it ideal for an off-grid system.
The combiner box works at a voltage of 250 V with a maximum of 10A on one PV input. Thus, the total input reaches 40A output. This capacity is enough for small to medium systems.
There’s a recommendation that you should not install the combiner box in direct sunlight and high ambient temperatures in the instruction manual. This could be a real bummer if you intend to install it on the roof like many other users. Even though the combiner box is compact and weighs 4.5 pounds, this limitation deterred us. But if you plan your setup in a shaded area, this combiner box is worth your consideration.
- Lightweight and compact
- Surge, short circuit, and lightning protection
- Prevents reverse current
- Easy to install and relocate
- Ideal for small to medium systems
- Perfect for an off-grid system
- Should not be set up under direct sunlight
- High temperatures reduce its longevity
8. ENZPOWER IP66 Combiner Box
If you’re looking for a compact combiner box with high efficiency, the ENZPOWER IP66 is the best solar combiner box for you. A feature that distinguishes this combiner box from others is its weight. At just 1.73 pounds, it’s the lightest combiner box on this list. The weight makes it both easy to set up and portable.
This combiner box is proof that size is not a measure of performance. It has 32A photovoltaic DC switches with special connectors. It comes with a disconnect switch as well. Also, its load breaking is up to 8 times the rated current, and it has double breaks with silver rivets. The manufacturers suggest that this solar combiner box can be used for both homes and commercial areas. It is also suitable for both on-grid and off-grid systems.
We found this combiner box to have an ergonomic design and high efficiency. As good as it may be, it lacks the advanced safety capabilities that the other combiner boxes possess. Combiner boxes are vulnerable to surges in voltage and short circuits. There should be measures to protect the system against them.
- Lightweight and compact
- Easy to relocate and install
- High efficiency and performance
- Suitable for both off-grid and on-grid setups
- It comes with a padlock for a tamper-proof enclosure
- Load breaking is 8 times the rated current
- Lacks advanced safety capabilities
What is a Solar Combiner Box?
In a photovoltaic array, multiple solar photovoltaic modules need to be connected to build up the input voltage required for the inverter. Simply put, a solar combiner box combines the input from multiple photovoltaic modules and feeds it to an inverter. That is, a combiner box combines the wires from these solar panels and their output into a single box.
Each of the cables is connected to a different fuse. From there, all the fuses send their output into a single line that goes into the inverter.
Newer models of combiner boxes also house other components like a surge protection device and robust data tracking hardware. These extra components expand the functionality of the combiner box.
Still unclear? Watch the explainer video below:
Do I need a solar combiner box?
Whether you need a solar combiner box or not depends on how many strings there are. For instance, if you are working with just two or three, you might not need to use combiner boxes. However, if you have more than three, you will need a combiner box.
Make sure that the combiner box that you choose has the correct number of inputs so that you can plug in each lead. You should have an idea about the total output as well.
Overall, using a combiner box can offer the following advantages:
- Protection from high current and high voltage
- It helps reduce cost on large scale projects
- It helps maximize the power output in an extensive system
- Reduces overall maintenance cost
- Make the system more manageable by reducing the number of leads going into the inverter.
- Can improve efficiency
In short, you do not always need a combiner box. But you can enjoy all the benefits mentioned above if you install it in your system. Also, if you are working with more than three strings, then a combiner box is mandatory.
How do you wire Solar Panels to a Combiner Box?
Let’s suppose that you have 12 photovoltaic modules in your system. Intuitively, you might decide to combine the negative and positive leads to a charge controller, which would then link with the interval. But this would result in a total of 24 input leads going into the inverter. Now that is not an excellent way to manage the solar panel’s positive and negative wire system.
At the same time, you might also plan to put all the connections together. However, that would result in a dangerously high voltage. So, you must divide the panel leads into three sets. These will go into the combiner box (or combiner boxes if you’re using multiple boxes). Here, these leads will then convert into a single wire that will connect with inverters.
If you are wondering how to install combiner boxes, make sure to read the instruction manual. All products that we have listed above come with a user manual that will take you through the entire setup process.
WARNING: Never try to inspect wiring or carry out maintenance with a live electrical connection. The high voltage could be fatal.
What does a combiner do?
The purpose of a combiner box is to manage a series of photovoltaic panels to enhance their function. In the market, you can now find combiner boxes with many safety measures. These deal with reverse current, surge, and voltage overload problems.
The best solar combiner box would typically have features such as fault failure coupled with high-end construction and other advanced capabilities. Wondering what traits you should look for in a combiner box? Let’s take a look at them.
What Features To Look For in Combiner Boxes?
Some combiner boxes can manage separate systems. However, not every combiner box is capable of that. Some might only be suitable for a single system. At the same time, some provide a higher level of safety capabilities, for example, to prevent a short-circuit fault or surges. Here are some features for you to consider.
Ease of Installation
Most of the modern combiners support DIY. But some of them are difficult to set up. If you don’t have experience with electrical devices, it’s best to consult a professional, especially if you want to combine multiple systems.
A solar panel combiner box is generally a low-maintenance device. But if you are fixing leaks and loose connections often, you didn’t install the combiner box properly. So you might need to set it up from scratch. That’s why a combiner box that’s difficult to install is not just a hassle; you might do it wrong and have problems in the future.
Many users don’t realize this, but the enclosure is one of the most critical components of a combiner box system. Unfortunately, it is also among the expensive components in the combiner box.
The proper enclosure will make sure that it lasts for a long time. Your combiner box is going to be outside, facing the elements. That’s why it should be waterproof and resistant to corrosion, especially if you have rainy weather with high humidity.
A non-metallic enclosure or an aluminum one with a plastic interior meets these requirements. You should check for humidity tolerance as well.
If you live in a hot climate, try placing the combiner box in the shade or a wall that doesn’t face the sunlight. The enclosure’s color also plays a role in how well it can handle a high temperature. You should avoid a dark-colored enclosure because it absorbs radiation.
First of all, you must ensure that the combiner boxes you are using fulfill the codes of your jurisdiction. They must also have fault failure and other rapid failure solutions.
Some combiner boxes have more advanced capabilities to safeguard your setup than others. For example, some of them protect against lightning and over-voltage, and some do not. Most people install combiners in off-grid systems. These areas are prone to lightning and surges, so this feature is a must-have if you live in that climate.
You should also check for a reverse-current prevention system, anti-backflow diodes, and a breaker is included in the package. Finally, make sure that the combiner box you buy can support your solar power system. It’s not a good idea to push the combiner box to its limits.
The ECO-WORTHY 6 String PV Combiner Joint Box is the best solar combiner box on our list. It is an all-rounder with high efficiency and advanced safety measures. However, the best combiner box for you can be different, depending on your location and requirements. For instance, sturdy placement will be an essential feature for you if you live on rough terrain. In that case, we recommend the AIMS POWER Com3in60A.
Another scenario is if you have a solar energy system with more than six strings, our top pick won’t work for you. You will need, for example, the Midnite Solar Mnpv12 Combiner Box. This model supports up to 10. So go through all the options on our list and find a combiner box that meets your needs. Moving forward, some modern features that we want to see in a combiner box are monitoring and data-tracking. So if you find a combiner box with monitoring for temperature, power output, humidity, etc., don’t hesitate to give it a try. Got any box that you feel should be on our list, kindly leave a comment below.