EG4 FlexBOSS21 21kPV Hybrid Inverter

Featuring 3 MPPT inputs supporting up to 5 strings, the FlexBOSS21 maximizes solar production while efficiently managing energy from solar, battery, grid, and generator sources. With 90A grid feed-through, it supports high-demand loads and seamless system integration.

Designed to integrate with the EG4 GridBOSS MID gateway, the system enables advanced energy control including smart load management, AC coupling, and generator support, while simplifying installation and reducing system costs. Built-in protections such as rapid shutdown, ground fault, and arc fault protection ensure safe and code-compliant operation.

With Wi-Fi connectivity, remote monitoring, and mobile alerts, the FlexBOSS21 provides full system visibility and control, making it a reliable, scalable solution for modern energy independence.

Ships From: Texas, USA
Warranty: 10 Years
Support: Lifetime USA-Based Tech Support

Compatibility

UL 9540 Certified + Closed-Loop Communication (Grid-Tied + Off Grid):

• BigBattery ETHOS
• EG4 Batteries

Power Compatibility:

• Works with 48V battery systems
• Supports grid-tied, hybrid, and off-grid installations
• AC coupling compatible for system upgrades and retrofits
• Integrates with EG4 GridBOSS MID for advanced system control

Key Features

• 16,000W Output Power – High-capacity split-phase power for residential and commercial systems
• 21,000W PV Input Capacity – Maximizes solar production for large systems
• 3 MPPT Inputs (Up to 5 Strings) – Optimized solar harvesting and flexible design
• Split-Phase 120/240V Output – Powers both standard and heavy-duty loads
• 90A Grid Feed-Through – Supports high-demand loads and seamless grid integration
• GridBOSS Integration – Enables advanced load management, AC coupling, and generator support
• Advanced Safety Protections – Includes rapid shutdown, ground fault, and arc fault protection
• Smart Energy Management – Supports peak shaving and intelligent power distribution
• Remote Monitoring & Alerts – Real-time system tracking via Wi-Fi and mobile app
• Flexible System Design – Ideal for grid-tied, hybrid, and off-grid installations
• Installer-Friendly Design – Reduces installation time and system complexity
• Maintenance-Free Operation – No routine servicing required

A high-performance hybrid inverter built for scalability, flexibility, and advanced energy control in modern energy systems.

Downloads & Specifications

Nominal AC Voltage:120/240VAC | 120/208VAC (L1/L2/N required)

Frequency:60 Hz (Default) | 50 Hz

Max. AC Current:50A @ 240V | 57.7A @ 208V

Max. AC Input Power:12000W

Max. AC Bypass:90A

Operating Voltage Range:180 – 270VAC

Output Voltage:120/240VAC | 120/208VAC (L1/L2/N required)

Max. Output Current:66.7A

Output Frequency:60 Hz (Default) | 50 Hz

Nominal Output Power (without PV):12000W @ 240V | 12000W @ 208V

Nominal Output Power (with PV):16000W @ 240V | 13800kW @ 208V

Power Factor:0.99 (Full Load)

Reactive Power Adjustment Range:-0.8 – 0.8 Leading Adjustable

Total Harmonic Distortion:<5% (Full Load)

Transfer Time:20ms (Default) | 10ms (Configurable) | 20ms (Parallel)

Rated Output Current:50A @ 240V | 57.7A @ 208V

Nominal Output Voltage:120/240VAC | 120/208VAC

Rated Output Power:12000W @ 240VAC | 12000W @ 208VAC

Peak Power:24000W (0.5 sec) | 18000W (1 sec)
15000W (6 min) | 13200W (12 min)

Operating Frequency:60 Hz (Default) | 50 Hz

Total Harmonic Distortion Voltage:<5%

Transfer Time:20ms (Default) | 10ms (Configurable) | 20ms (Parallel)

No. of MPPTs:3

Inputs per MPPT:2 (MPPT 1) | 2 (MPPT 2) | 1 (MPPT 3)

Max. Usable Input Current:26A (MPPT 1) | 26A (MPPT 2) | 15A (MPPT 3)

Max. Short Circuit Input Current:31A (MPPT 1) | 31A (MPPT 2) | 19A (MPPT 3)

DC Input Voltage Range:100 – 600VDC

Unit Start-Up Voltage:100VDC

MPPT Operating Voltage Range:120 – 440VDC

Nominal MPPT Voltage:360VDC

Max. Utilized PV Array Power:21000W

Max. Recommended PV Input:25000W

Max. Efficiency:97% (PV to Grid) | 94.5% (PV to Battery) | 94% (Battery to Grid)

Idle Consumption:<65W

Nominal Voltage:48VDC

Voltage Range:40 – 60VDC

Max. Charge / Discharge Power:12000W

Recommended Battery Capacity per Inverter:>300Ah

Operating / Storage Temperature Range:-13ºF – 140ºF (-25ºC – 60ºC)

Operating Altitude:<6,561 ft (2000 m)

Relative Humidity:0 – 100%

Typical Noise Emission:<50dB @ 3 ft

Design Topology:High-Frequency / Transformerless

Protection Rating:IP65 / NEMA 4X

Communications:RS485 / CANBus / WiFi

Max. Parallel Connections:16

Weight:88 lbs (40 kg)

Depth:11.3 in (287 mm)

Width:22.3 in (567 mm)

Height:30.5 in (775 mm)

Inverter Downloads

SKU#:INV027

Spec Sheet:DOWNLOAD

User Manual:DOWNLOAD

UL1741 Certificate:DOWNLOAD

CEC Listing- EG4 FlexBoss21:GO TO LINK

Warranty

10-Year EG4 Manufacturer Warranty