If you’ve been building your own off-grid power system, you know the struggle — finding a clean, organized, and weatherproof way to store your solar batteries and inverters.
Wall-mounting 2,000 pounds of lithium batteries isn’t exactly ideal, and giving up half your garage to server racks isn’t much better. That’s where the EG4 BOSSBox ESS Enclosure comes in: a steel, all-weather energy storage enclosure designed to safely store your entire solar setup outdoors.
With capacity for up to 43 kWh of battery storage and 32kW of inverter output, the BOSSBox isn’t just a cabinet, it’s a complete solar battery housing system built for real homes, cabins, and even small businesses looking to expand their backup power setup.
When we visited Signature Solar down in Texas earlier this year, we saw our first BOSS Box up close. It stood out to us right away, as they had one out in the parking lot powering their solar EV charger. It looked sleek, professional, and far more “put-together” than the usual plywood shed or metal cabinet we’ve seen used for other off-grid battery installations.
Fast forward a few months, and we finally got our hands on one for testing here at The Solar Lab. We’ve been using it long enough to see what it’s great at, and where it falls short.
Spoiler Alert: it’s not a perfect battery storage solution, but we think it could offer a lot of homeowners some really practical benefits.
Before we dive into everything we like about this weather-resistant energy storage enclosure, let’s take a quick look at what it’s supposed to bring to the table:
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Assembly was surprisingly easy, and all of the panels fit together smoothly. The overall design is simple enough that two people could assemble it in a single afternoon.
One thing we quickly learned, though: build it where you want it to stay. Since the batteries form part of the enclosure’s structure, moving it after assembly means disassembling parts of it. We thought we’d put it together in the middle of the backyard for filming purposes, so getting it into our garage afterwards was a real team effort.
Speaking of which, we actually wanted to test the portability of the BOSSBox when we first decided we were going to review it. Thanks to its integrated base, you can pick it up with a forklift or pallet jack, even when it’s fully loaded with batteries and inverters.
That makes it a great choice for installers or anyone who might move their system later, say from one property to another. We understand that most home owners aren’t going to have a forklift handy, but knowing it is portable at all is going to make it an attractive option to those who would otherwise have to build a permanent shelter for their outdoor batteries and inverters.
During our weather testing, we actually got quite a bit of rain, which the BOSS Box ESS was able to handle quite easily. We then simulated heavy rainfall using a garden hose, which allowed us to see how the unit handled prolonged and direct exposure to moisture. While it performed well overall, a bit of water did seep in through the door seams. This is something we’ll come back to later.
Now that we’ve covered the basics, let’s jump into all of the things we like (and dislike) about this all-in-one energy storage enclosure:
The epoxy-coated steel construction feels durable and premium. Unlike DIY battery sheds or wooden enclosures, this looks like it belongs next to a Generac backup system or a professional grid-tied installation. It’s the kind of setup you wouldn’t mind showing off, as it’s sleek, modern, and functional.
For something like Josh’s tiny home rental or even Dylan’s off-grid cabin, something like this would be ideal. Both had to construct permanent structures to house their batteries and inverter, so this would eliminate the need for all of that hard work.
From an installer’s perspective, the forklift-friendly base is a major win. You can assemble it indoors out of the rain, and then move the entire unit (with batteries and inverters installed) right to where you need it to be.
That’s a huge time-saver for commercial or mobile setups, especially if you’re running event power or managing remote backup energy systems. For homeowners with even the slightest DIY abilities, it’s also something that could be installed as a weekend project. So, whether you’re a professional solar installer or just a homeowner looking for a more practical power storage solution, the BOSSBox fits the bill.
The BOSSBox supports a range of EG4 inverters, including the hugely popular 12kPV and 18kPV, as well as the models in the new FlexBOSS series.
You can mix and match configurations, like having one inverter tied to one battery or two inverters sharing three. Basically, you can work out any sort of combination that will fit your needs. Again, this flexibility makes it ideal for both residential solar storage and off-grid cabins.
If you rent your home, plan on moving, or just don’t have the option to mount heavy batteries inside your home, this is a fantastic alternative.
It keeps everything outdoors, secure, and weather-resistant, while freeing up space inside your garage or basement. Plus, it’s completely relocatable if you move, which is a rare feature in the solar battery storage world.
Since the EG4 WallMount All Weather Batteries it’s designed to work with are suitable for outdoor use, the BOSSBox perfectly complements any sort of outdoor power storage system.
While there was a lot we liked about this thing, few pieces of solar equipment are perfect, and the EG4 BOSS Box is no exception. Here are a few of the issues we found when we were testing it:
Our unit arrived with a dented roof panel, likely due to improper packaging. The top sheet metal is thin enough that heavier items that came shipped in the box likely caused small dings. We also ran into misaligned bolt holes on one side of the interior battery divider, which slowed assembly and required a bit of adjustment.
None of these are major issues, but this is an outdoor battery cabinet that costs about $2,500, even with our discount code. For that type of money, you’d expect it to arrive in flawless condition.
Although it’s built for outdoor use, we found some minor water ingress during our rain simulation test. The bottom interior became damp after extended exposure. A simple rubber door gasket would likely fix this issue, and we hope that’s something EG4 considers in future versions of the BOSSBox.
Luckily, all of the components that work with the BOSSBox are designed to be water-resistant, but who wants pooled water around expensive solar batteries?
The standard battery cables included with EG4’s WallMount Batteries are too short for use inside the enclosure. Since these batteries were designed to be mounted on a wall directly beside your inverter, they just don’t have the length to reach outside of the BOSSBox and plug into the inverter.
This means you’ll need to purchase longer cables separately to reach the inverters. It’s a small annoyance, but at this price point, a plug-and-play package option would make sense.
Our older EG4 All-Weather Batteries lacked the new threaded feet needed for secure mounting inside the BOSSBox. That means if you bought EG4 batteries before mid-2024, you’ll need the new models with adjustable feet to install them properly.
If you’re starting from scratch and ordering your batteries with the BOSSBox, which is something Signature Solar actually offers as a bundle, this won’t be an issue. However, if you’re hoping to enclose your existing batteries, you’ll have to double-check for compatibility.
If you’re serious about off-grid power or whole-home solar backup, the EG4 BOSSBox is built for you. It’s especially ideal for:
With the capacity for up to 43 kWh of battery storage, it can hold more power than most homes use in a full day. This makes it perfect for those preparing for long-term power outages, building an outdoor solar EV charging setup, or just looking for a neat way to house their solar equipment at an off-grid property.
If you’re feeling like you don’t know where to start with solar batteries, you can also read our beginner-friendly guide: Sizing Battery Capacity for a Solar Power System
The EG4 BOSSBox Energy Storage Enclosure isn’t perfect, but it’s one of the smartest and most versatile solar battery storage solutions we’ve tested.
It solves a real-world problem: how to safely, neatly, and professionally store high-capacity backup power systems outdoors.From build quality to flexibility, it’s a product that genuinely stands out in the solar industry.
With a few small improvements, like better sealing and longer cables, we’d probably recommend it for most off-grid and hybrid power systems. For now, it’s a product that we think will really help a lot of people, but it probably isn’t going to be something we’d recommend to everyone.
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