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48V Hybrid Inverter · Dual MPPT · Built-In 4G · UL 9540
The EG4 FlexBOSS18 is rated for 13,000W of continuous output, backed by up to 18,000W of PV input across two MPPT trackers and four solar strings. It works grid-tied or fully off-grid, integrates with EG4's GridBOSS energy management hub, and connects over Wi-Fi or built-in 4G — useful anywhere a reliable internet connection isn't a given. Backed by a 10-year manufacturer's warranty inside a NEMA 4X all-weather enclosure.
Rated for 13,000W continuously, with peak power up to 20,000W for half a second to cover large motor starts.
Two MPPT trackers split across four total input strings, pulling up to 18,000W utilized from the array.
Communicates over RS485, CANBus, Wi-Fi, or built-in 4G — remote monitoring stays online even without a local Wi-Fi network.
Connects directly to EG4's GridBOSS hub for smart load management, AC coupling, and generator support at a system level.
Handles high-demand loads and grid integration with headroom beyond what most residential hybrid inverters offer.
UL 9540 certified for both grid-tied and off-grid installs with compatible batteries — the same unit covers either path.
Rated for direct outdoor installation and built to keep running through rain and snow, not just covered or indoor spaces.
Scales from a single large home up to bigger residential or light commercial installations on the same platform.
The FlexBOSS18 sits between EG4's 12kPV and FlexBOSS21 by power — 13,000W continuous output and up to 18,000W of PV input across two MPPT trackers and four strings. What it adds that the larger FlexBOSS21 doesn't list is built-in 4G connectivity alongside Wi-Fi, which matters for installs in areas with unreliable or absent local internet: remote monitoring and alerts keep working over cellular instead of depending on a home network staying up.
Like the rest of EG4's hybrid line, it's UL 9540 certified for both grid-tied and off-grid installs with BigBattery ETHOS or EG4 batteries, integrates with EG4's GridBOSS hub for system-level load management and AC coupling, and ships in a NEMA 4X enclosure rated for direct outdoor installation. A 10-year manufacturer's warranty and up to 10 parallel units round out a unit built for serious residential systems that don't quite need the FlexBOSS21's full scale.
| Continuous output power | 13,000 W |
| Output voltage | 120/240V, 120/208V |
| Max AC current | 54A @ 240V/208V |
| Max output current | 66.7 A |
| Peak power (0.5s / 1s) | 20,000W / 15,000W |
| Power factor | 0.99 (full load) |
| Transfer time | 20ms default / 10ms configurable |
| MPPT channels | 2 (4 strings total) |
| Max utilized PV power | 18,000 W |
| Max usable input current | 26A + 26A |
| DC input voltage range | 100–600 Vdc |
| MPPT voltage range | 120–440 Vdc |
| Max efficiency (PV to grid) | 97.5% |
| Nominal battery voltage | 48 Vdc |
| Battery voltage range | 40–60 Vdc |
| Max charge/discharge power | 10,000 W |
| Rec. battery capacity/inverter | >300 Ah |
| Max AC bypass | 90 A |
| Idle consumption | <65 W |
| Dimensions (D×W×H) | 11.2 × 22.8 × 30.5 in |
| Weight | 115 lbs |
| Enclosure rating | NEMA 4X (all-weather) |
| Operating temperature | -13°F to 140°F |
| Noise level | <50 dB @ 3 ft |
| Design topology | High-frequency, transformerless |
| Communication | RS485 / CANBus / Wi-Fi / 4G |
| Max parallel units | 10 |
| Brand / model | EG4 FlexBOSS18 |
| Warranty | 10 years |
Certification: UL 1741, UL 9540.
UL 9540 certified with closed-loop communication for both grid-tied and off-grid installs, when paired with:
13,000W is what the FlexBOSS18 delivers continuously. Peak power goes higher for short bursts — up to 20,000W for half a second, tapering down to 11,000W over 12 minutes — which covers the brief surge a motor or compressor needs to start without requiring that much power all the time.
Both — it communicates over RS485, CANBus, Wi-Fi, and built-in 4G. The 4G option matters for installs where a reliable local Wi-Fi network isn't available; remote monitoring and alerts can run over cellular instead.
The EG4 GridBOSS is a separate energy management hub (sold separately) that adds smart load management, AC coupling, and generator support at a whole-system level. It's an optional add-on — the FlexBOSS18 runs as a complete inverter on its own.
Yes — it carries a NEMA 4X enclosure rating, built for direct exposure to rain and snow, unlike IP20-rated inverters that require an indoor or fully enclosed location.
It's UL 9540 certified for both grid-tied and off-grid installs with BigBattery ETHOS and EG4 batteries, with at least 300Ah of recommended capacity per inverter.
It depends on your total connected load. At 13,000W continuous, it covers most homes comfortably, but a full load calculation is worth doing before sizing your system, especially for larger properties with heavy HVAC or well pump draw.
Given the voltages and currents involved, and the added complexity of a grid-interactive hybrid system, installation should be handled by a qualified, licensed electrician or solar installer familiar with your local code and utility interconnection requirements.
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To start a return: +1 (307) 317-7213, hello@ecosolarkits.com, or live chat. Read the full return and refund policy
