When configured as a UL 9540 certified ESS: <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="7" data-aria-level="1"> EG4 FlexBOSS21 Hybrid Inverter : UL 1741 <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="8" data-aria-level="1"> EG4 WallMount All Weather Battery : UL 1973, UL 9540A <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="9" data-aria-level="1"> Min Configuration : 1 EG4 FlexBOSS21 All-in-One Hybrid Inverter and 1 EG4 WallMount All Weather Battery <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="10" data-aria-level="1"> Max Configuration : 3 EG4 FlexBOSS21 All-in-One Hybrid Inverters and 6 EG4 WallMount All Weather Batteries <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="11" data-aria-level="1"> Total Output Power (kW) : 16kW-48kW @ 240V, 13.8-41.4 kW @ 208V (on-grid with PV) <li aria-setsize="-1" data-leveltext="" data-font="Symbol" data-listid="3" data-list-defn-props="{"335552541":1,"335559685":720,"335559991":360,"469769226":"Symbol","469769242":[8226],"469777803":"left","469777804":"","469777815":"hybridMultilevel"}" data-aria-posinset="12" data-aria-level="1"> 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. California Proposition 65 Warning

EG4 FlexBOSS21 + WallMount All Weather Battery ESS

ESS

EG4 FlexBOSS21 + WallMount All Weather Battery ESS

ESS

EG4®-FlexBOSS21-WallMount-All-Weather-Battery-Energy-Storage-System.webp

EG4®-FlexBOSS21-WallMount-All-Weather-Battery-Energy-Storage-System-2.webp

The EG4® FlexBOSS21 WallMount All Weather Battery Energy Storage System (ESS) delivers dependable power for your home, indoors or out. When the grid goes down, it seamlessly powers your essentials—think lights, appliances, or even your garage workshop—keeping your routine uninterrupted. Built to withstand tough outdoor conditions with integrated heating, it’s perfect for any environment.

Installer-trusted and homeowner-friendly, this system offers high performance without the high cost. Check its status from your phone and scale it up as your needs evolve. UL 9540 certified, it’s designed to keep your home powered with confidence.

Features & Benefits

Uninterrupted Power:
Seamless backup for essential systems during outages.

Outdoor Durability:
Weather-resistant design for reliable outdoor performance.

High Capacity:
Up to 16kW output for demanding applications.

Flexible Use:
Supports on-grid and off-grid configurations.

Easy Installation:
Plug-and-play setup for quick deployment.

Scalable System:
Expand to meet future energy demands.

Smart Monitoring:
Remote tracking for performance insights.

Certified Safety:
ETL listed to UL 9540 for peace of mind.

Key Specifications

When configured as a UL 9540 certified ESS:

EG4 FlexBOSS21 Hybrid Inverter: UL 1741

EG4 WallMount All Weather Battery: UL 1973, UL 9540A

Min Configuration: 1 EG4 FlexBOSS21 All-in-One Hybrid Inverter and 1 EG4 WallMount All Weather Battery

Max Configuration: 3 EG4 FlexBOSS21 All-in-One Hybrid Inverters and 6 EG4 WallMount All Weather Batteries

Total Output Power (kW): 16kW-48kW @ 240V, 13.8-41.4 kW @ 208V (on-grid with PV)

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.

California Proposition 65 Warning