Big Battery EG4 FlexBOSS18 13kW (18kPV) Hybrid Inverter

The latest development from the EG4 team, the FlexBOSS18 is a cutting-edge, split-phase hybrid inverter designed to be the keystone of any residential or commercial power system. With an incredible 18kW PV input capacity and an array of advanced features, the FlexBOSS18 provides reliable performance day in and day out, in both on-grid and off-grid settings.
The FlexBOSS18 is one of the highest capacity inverters on the market today, featuring 2 MPPTs supporting up to 4 strings, providing superior flexibility for multi-orientation solar arrays, and the ability to handle 90A of grid feed-through at 120/240VAC, ensuring robust grid-tied capabilities. Plus, the FlexBOSS18 seamlessly integrates with EG4’s GridBOSS MID power gateway for a cost-effective, streamlined setup, helping to reduce installation time and system startup costs, and when you pair these two units together in your system, you’re able to utilize the smart load management, AC coupling, and generator support features if needed.
But that’s not all. EG4 understands the value of enhanced safety and visibility when it comes to your power, and the FlexBOSS18 spares no expense, coming equipped with responsive rapid shutdown, ground fault monitoring, and arc fault protection, all backed by industry-leading safety certifications, and with EG4’s updated monitoring software, you get access to remote management, mobile notifications, and convenient Wi-Fi connectivity for your system.
Combining efficiency, scalability, and cutting-edge technology, the FlexBOSS18 is a top-tier solution, with a safety-first design, for those seeking a reliable, powerful inverter to anchor their energy system. Whether for residential or commercial applications, its advanced features and versatile design provide unmatched value and peace of mind. Elevate your energy independence and power your future with the EG4 FlexBOSS18 Hybrid Inverter today.
Tech Specs
AC INPUT





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


Frequency:
60 Hz (Default) | 50 Hz


Max. AC Current:
54A @ 240V | 54A @ 208V


Max. AC Input Power:
13000W


Max. AC Bypass:
90A



AC GRID OUTPUT





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)



AC BACKUP / UPS OUTPUT





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


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


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


Peak Power:
20000W (0.5 sec) | 15000W (1 sec)12500W (6 min) | 11000W (12 min)


Operating Frequency:
60 Hz (Default) | 50 Hz


Total Harmonic Distortion Voltage:
<5%


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



PV INPUT





No. of MPPTs:
2


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


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


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


DC Input Voltage Range:
100 – 600VDC


Unit Start-Up Voltage:
200VDC


MPPT Operating Voltage Range:
120 – 440VDC


Nominal MPPT Voltage:
360VDC


Max. Utilized PV Array Power:18
18000W


Max. Recommended PV Input:
18000W


Max. Efficiency:
97.5% (PV to Grid) | 94.5% (PV to Battery) | 94% (Battery to Grid)


Idle Consumption:
<65W



BATTERY





Nominal Voltage:
48VDC


Voltage Range:
40 – 60VDC


Max. Charge / Discharge Power:
10000W


Recommended Battery Capacity per Inverter:
>300Ah



OPERATING ENVIRONMENT





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 / 4G


Max. Parallel Connections:
10



DIMENSIONS





Weight:
115 lbs (52 kg)


Depth:
11.2 in (287 mm)


Width:
22.8 in (567 mm)


Height:
30.5 in (775 mm)

Orders ship within 1–5 business days. Shipping rates vary by order and destination. We ship across the U.S., with additional charges for Hawaii and Alaska. For damaged, lost, or delayed orders, please contact us for assistance.

Most products include a 12-month limited warranty covering manufacturer defects. Warranty terms may vary by product, especially lithium batteries and electrical components. Damage from improper installation, misuse, or normal wear is not covered.

Returns are accepted within 30 days of delivery for a full refund or exchange. Items must be new, unused, and undamaged, with the original order number provided. Customers are responsible for return shipping on unwanted or incorrectly ordered items. Lithium batteries must be unused and sealed to qualify for return. Damaged, defective, or incorrect orders should be reported immediately.