EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring
EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring - Image 2
EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring - Image 3
EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring - Image 4
  • U.S. Support

EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring

SKU# INV027

Change inverter or battery

Loading specifications…
SKU: INV027 Categories: , ,
$4,199.99$3,599.99
YOU SAVED: $600.00
Orders over $3,000 Qualify For Free Shipping!
Add to cart for 7% OFF

-

Additional Add-ons

Documents & Certifications

About this item

The EG4 FlexBOSS21 Hybrid Inverter is a high-capacity, next-generation solution designed for advanced residential and commercial energy systems. With support for up to 21,000W PV input and 16,000W split-phase (120/240V) output, it delivers powerful, flexible performance for both on-grid and off-grid applications.

 

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 PowerHigh-capacity split-phase power for residential and commercial systems
  • 21,000W PV Input CapacityMaximizes solar production for large systems
  • 3 MPPT Inputs (Up to 5 Strings)Optimized solar harvesting and flexible design
  • Split-Phase 120/240V OutputPowers both standard and heavy-duty loads
  • 90A Grid Feed-ThroughSupports high-demand loads and seamless grid integration
  • GridBOSS IntegrationEnables advanced load management, AC coupling, and generator support
  • Advanced Safety ProtectionsIncludes rapid shutdown, ground fault, and arc fault protection
  • Smart Energy ManagementSupports peak shaving and intelligent power distribution
  • Remote Monitoring & AlertsReal-time system tracking via Wi-Fi and mobile app
  • Flexible System DesignIdeal for grid-tied, hybrid, and off-grid installations
  • Installer-Friendly DesignReduces installation time and system complexity
  • Maintenance-Free OperationNo routine servicing required

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

EG4 FlexBoss21 Inverter - Simply scalable
UL1741 Certified
Power stays on in storm and rain - EG4 FlexBoss21 Inverter
Power endures snow - EG4 FlexBoss21 Inverter
GridBoss - EG4 FlexBoss21 Inverter
EG4 lineup

.

Inverter Downloads

SKU#:INV027
Spec Sheet:DownloadDOWNLOAD
User Manual:DownloadDOWNLOAD
UL1741 Certificate:DownloadDOWNLOAD
CEC Listing- EG4 FlexBoss21:Go to linkGO TO LINK

Inverter 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)

Compare Inverter

10-Year EG4 Manufacturer Warranty

EG4 FlexBoss21 Inverter - Simply scalable
UL1741 Certified
Power stays on in storm and rain - EG4 FlexBoss21 Inverter
Power endures snow - EG4 FlexBoss21 Inverter
GridBoss - EG4 FlexBoss21 Inverter
EG4 lineup

.

See More On YouTube

Inverter Downloads

SKU#:INV027
Spec Sheet:DownloadDOWNLOAD
User Manual:DownloadDOWNLOAD
UL1741 Certificate:DownloadDOWNLOAD
CEC Listing- EG4 FlexBoss21:Go to linkGO TO LINK

Inverter 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)

Compare Inverter

10-Year EG4 Manufacturer Warranty

Frequently Asked Questions

FlexBOSS21 or FlexBOSS18: which should I get?

The FlexBOSS21 gives 16,000W output with 21,000W PV input and 3 MPPTs supporting up to 5 strings. The FlexBOSS18 gives 13,000W output with 18,000W PV input. Choose the 21 for large arrays, all-electric homes and light commercial. The 18 covers most residential builds.

How many solar strings can the FlexBOSS21 take?

Three MPPT inputs supporting up to five strings, which gives real flexibility on roofs with multiple orientations or partial shading. More MPPTs means arrays facing different directions can be optimised independently rather than dragged down by the weakest string.

Is the FlexBOSS21 UL 9540 certified with EG4 batteries?

Yes. It is UL 9540 certified with closed-loop communication for grid-tied and off-grid operation, with BigBattery ETHOS and EG4 batteries listed as compatible. It is also one of the inverters certified with the EG4 314Ah WallMount batteries.

Do I need a GridBOSS for the FlexBOSS21?

No, but it integrates with the GridBOSS 200A MID for advanced system control including smart load management, AC coupling and generator support. On a system this size, most installs benefit from the load management the GridBOSS provides.

Is the FlexBOSS21 suitable for commercial use?

It is built for advanced residential and commercial energy systems, with 90A grid feed-through, rapid shutdown, ground fault and arc fault protection, and Wi-Fi monitoring with mobile alerts. It is the largest inverter in the EG4 hybrid range.

×

You May Also Like

Related products based on what you're viewing

EG4 FlexBOSS21 Hybrid Solar Inverter | 21kW PV / 16kW AC | Split-Phase | 4-MPPT | Scalable | Remote Wi-Fi Monitoring