EG4® FlexBOSS21 + 280Ah WallMount Indoor Battery ESS
UL 9540 Certified
The EG4® FlexBOSS21 280Ah WallMount Indoor Energy Storage System (ESS) ensures your home stays powered, no matter what the grid does. When a storm knocks out electricity, this system kicks in instantly, keeping your essentials—like your refrigerator or home office equipment—running smoothly. Its easy setup and built-in heating make it perfect for indoor spaces like utility rooms with little climate control.
Designed with installer expertise in mind, it offers powerful performance at a price that fits your budget. Monitor your system on your phone and expand it later if you need more power. Certified to UL 9540 standards, it’s a reliable choice for worry-free home backup.
Reliable Power:
Maintains critical loads during outages, supporting essential systems.
High Capacity:
Powers demanding appliances with up to 16kW output.
Versatile Design:
Supports on-grid and off-grid applications for maximum flexibility.
Simple Setup:
Plug-and-play installation saves time and effort.
Scalable Solution:
Add units to match your energy needs.
Remote Monitoring:
Stay informed with real-time performance tracking.
Certified Safety:
ETL listed to UL 9540 for trusted operation.
When configured as a UL 9540 certified ESS:
EG4 FlexBOSS21 Hybrid Inverter: UL 1741
EG4 WallMount Indoor 280Ah Battery: UL 1973, UL 9540A
Min Configuration: 1 EG4 FlexBOSS21 All-in-One Hybrid Inverter and 1 EG4 WallMount Indoor 280Ah Battery
Max Configuration: 3 EG4 FlexBOSS21 All-in-One Hybrid Inverters and 6 EG4 WallMount Indoor 280Ah Batteries
Total Output Power (kW): 16kW-48kW
Total Energy Capacity (kWh): 14.3-85.8 kWh
Additional capacity may be possible by spacing ESSs 3 ft apart per NFPA 855 and IRC R328 guidelines. Consult AHJ prior to installation for permissible configurations.
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FAQs
An Energy Storage System (ESS) is a collection of batteries, inverter(s) and other components that allow the storage of energy for later use. The term is most often used in conjunction with on-grid systems with batteries but could also be applied to off-grid systems.
Many jurisdictions require UL9540. To get this certification, the battery and inverter must pass stringent safety tests as a pair with specific configurations. An EG4 ESS is one that has been independently certified to pass these requirements using batteries and hybrid inverters. Even if your jurisdiction does not require a UL9540, choosing a UL9540 system gives you the peace of mind that the components have been tested by an independent lab to assure they work safely together.
Each system will be different, but the primary components of an ESS will include batteries, a hybrid inverter, a solar charge controller (usually bundled in the inverter) and solar panels. However, there will be many other smaller components (known as the balance of system) that are required to set up a system properly and safely. This can include things like wires, conduit, solar panel mounting hardware, switches, and fuses.
An ESS can store energy from many different sources. The most common source of energy stored by an ESS is solar, but any form of energy could be used in the system including renewable energy (solar power, wind power, hydro power), generator, grid, etc. An EG4 ESS is designed with a focus on energy from solar and the grid, as well as AC coupling (generators).
There are several reasons to install an Energy Storage System (ESS). One reason is to store energy generated from solar or other renewable sources for times when the primary source is unavailable. Another benefit is to power loads during grid outages, ensuring continuity of electricity supply. Additionally, an ESS enables the shifting of grid usage to off-peak hours, a practice known as peak shaving, which helps balance demand and alleviate strain on the grid during peak periods. Moreover, by facilitating the redistribution of grid usage to off-peak hours, the system contributes to grid stability by smoothing out demand fluctuations and reducing the occurrence of peak loads that the grid may struggle to accommodate.
Yes, depending on how the system is configured. An ESS can be optimized for load shifting, grid failures or a balance of both.
Yes. An ESS uses a hybrid inverter that is grid interactive, so it can be programmed to sell back to the grid at any time. Depending on the net metering program available for your utility, this can make a lot of sense financially.
Yes, you can add your existing system to certified EG4 ESS and classify it as EG4 ESS system. Please contact our technical support for more information.
EG4 system is designed for scalability. You can always add more batteries and inverters in the near future as your energy needs grows and classify your system as certified.
