EG4 FlexBOSS21 48V Hybrid All-in-One Inverter, 12kW-16kW AC Output, UL 1741 & UL 9540 Solar Inverter

Overview

Off-grid systems cost less with the EG4 FlexBOSS21, which trades a larger transfer switch for more output than the 18kPV. It is an all-in-one 120/240V hybrid inverter for 48V banks with 12kW continuous output, rising to 16kW with solar.

Planning a system? Read our guide: How to size a battery backup system for your home.

Key benefits

• 156A locked rotor rating starts a 5-ton air conditioner or large well pumps.
• Accepts 21kW of solar input across three MPPT trackers.
• NEMA 4X rating suits indoor, outdoor, and coastal installations.
• Total rapid shutdown with EG4 batteries removes the need for extra external battery disconnects.

Key features

• 90-amp transfer switch for partial backup of critical loads
• Up to 10 inverters can be scaled together
• RS485 and CANBus closed-loop communication
• Web monitoring for firmware updates and remote settings
• No onboard screen; one can be added
• UL 1741 and UL 9540

Ideal use

For homes and buildings blending solar, batteries, and grid, with an optional GridBOSS for generator and smart load control.

Key specifications

Model / SKU

EG4INV240V50AFLXBOSS

Brand

EG4

Category

Whole-home backup

Voltage

48V

Rated power

12,000 W

From the manufacturer

The EG4 FlexBOSS21 is an all-in-one hybrid, 120/240V inverter designed for a 48V battery bank. Multiple modes of operation can be adjusted to meet the needs of every stationary power application. The hybrid functionality of this inverter means it can blend grid, solar and batteries to supply loads and appliances in any home or building. The FlexBOSS21 has a 90-amp transfer switch and can provide partial backup for critical loads. Leverage batteries to offset grid usage during on-peak hours, and minimize grid consumption all together by generating power from solar panels. Off-grid applications are less expensive with the FlexBOSS21. Compared to an inverter like the EG4 18kPV, the larger transfer switch is traded for increased output capacity. Up to 10 FlexBOSS21 inverters can be scaled to cover the needs of demanding applications. Get more out of the FlexBOSS21 by pairing with the EG4 GridBOSS. While optional, the GridBOSS has comprehensive grid backup with generator and smart load capability. The GridBOSS grants flexibility in locating the FlexBOSS21, by segregating the connection to the home infrastructure. This is a NEMA 4X outdoor-rated unit which can be used inside or outside, even in areas with high humidity, intense rain or heavy dust. It even withstands the corrosive salt spray and damp environments found in coastal climates. This inverter is a highly capable powerhouse. The 156A locked rotor rating (LRA) is enough to start large loads such as a 5-ton air conditioner or large well pumps. The continuous AC output power of 12kW increases to 16kW when solar is present. As the name suggests, it can accept 21kW of solar input, simultaneously feeding batteries and AC loads. Three MPPT trackers support various solar array designs. Individual trackers are ideal for solar strings installed at different locations, angles and/or shading conditions. EG4’s web monitoring platform facilitates firmware updates, provides remote setting changes and displays data logs. Unlike other EG4 inverters, the FlexBOSS21 does not have an onboard screen, but one can be added. RS485 and CANBus closed-loop communication enables interoperability with many batteries. While best suited for use with EG4 batteries, it supports multiple protocols that are compatible with other brands. When paired with EG4 batteries, the inverter features EG4’s total rapid shutdown technology that de-energizes the entire system, including the batteries. This safety feature eliminates the need for additional external battery disconnects generally required by code.

Warranty terms mentioned in this description are the manufacturer’s. Our own coverage is the 30-day limited warranty.

Before you order

We confirm compatibility, installation requirements, and delivery details with you during order review, before any payment. Home electrical work may require a qualified installer.

Ask our team how the FlexBOSS21 compares with the 18kPV for your system. Message our team on WhatsApp.