EG4 EG4FLEXBOSS21 16kW Hybrid Inverter/Charger

EG4 FlexBOSS21 — 16kW Split-Phase All-in-One Hybrid Inverter | NEMA 4X | 21kW Solar Input | EMP Hardened

The EG4 FlexBOSS21 is the most capable inverter in EG4's FlexBOSS lineup — a 16kW split-phase hybrid inverter/charger built for large homes, demanding off-grid properties, and installations where maximum output, extreme load-start capability, and long-term environmental durability are non-negotiable. With 21,000W of solar input across three MPPT channels and five string inputs, 16,000W of continuous AC output when solar is present, a 156A locked-rotor amperage rating that can start a 5-ton air conditioner, a NEMA 4X coastal-rated enclosure, EMP hardening, and purpose-built integration with the EG4 GridBOSS MID — the FlexBOSS21 delivers a feature stack that stands alone in its class.

16kW Output with Solar, 12kW from Battery — Power a Large Home Without Compromise

The FlexBOSS21 delivers 12,000W of continuous AC output from battery alone, boosting to 16,000W when solar production is available — intelligently blending grid, solar, and battery to meet your home's full load without waste or manual switching. That 16kW solar-assisted output is enough to simultaneously run central HVAC, an electric water heater, a well pump, a workshop, EV charging, and normal household loads without shedding a single circuit. The 90A grid pass-through handles utility power flow seamlessly when the grid is available, with no external transfer switch required.

156A Locked Rotor Rating — Starts a 5-Ton Air Conditioner

Most competing inverters in the 12–16kW output range struggle with large motor-start loads. The FlexBOSS21 doesn't. Its 156A locked rotor amperage (LRA) rating provides the instantaneous current burst needed to start the most demanding residential loads — including 5-ton central air conditioning systems and large submersible well pumps — without voltage sag, false overload trips, or the need for a separate soft-starter. For homes in hot climates or rural properties with deep-well water systems, this real-world motor-start capability is a critical operational advantage.

21kW of Solar Input — Three MPPT Channels, Five String Inputs, 600VDC Max

Three independent MPPT charge controllers — rated at 26A, 26A, and 15A — support five separate string inputs across up to three distinct array orientations, accepting a combined 21,000W of PV input at up to 600VDC maximum. Five string inputs mean you can wire separate roof sections, different azimuths, or mixed panel configurations directly into the inverter without a combiner box, maximizing production independence across each array and eliminating shading losses between strings. The 600VDC ceiling allows longer, more efficient string designs with fewer parallel runs and lower balance-of-system costs.

EMP Hardened — Protection Against Electromagnetic Pulse Events

The FlexBOSS21 is one of the very few residential hybrid inverters on the market that is specifically engineered to withstand Electromagnetic Pulse (EMP) events — whether from natural geomagnetic disturbances or other disruptions. EMP hardening protects the inverter's critical electronics from the induced voltage spikes that would damage or destroy conventional inverter electronics, ensuring your energy system remains operational when conventional grid infrastructure and unprotected equipment may not. For off-grid preparedness and energy resilience applications, this is a feature with no direct equivalent among competing products.

NEMA 4X Enclosure — Coastal, Outdoor, and All-Weather Rated

The FlexBOSS21's NEMA 4X enclosure rating provides full protection against windblown dust, rain, hose-directed water, and corrosive salt spray found in coastal and marine environments — going meaningfully further than the IP65 or NEMA 3R ratings found on most competing hybrid inverters. Whether mounted outdoors in coastal Florida, on a Hawaiian hillside, in a Pacific Northwest outbuilding, or in a dusty agricultural equipment barn, the FlexBOSS21 is rated to operate reliably in conditions where other inverters simply aren't qualified to go.

GridBOSS MID Integration — One System, Zero Unnecessary Hardware

The FlexBOSS21 is purpose-built to pair with the EG4 GridBOSS MID, EG4's dedicated grid management gateway. Together, the FlexBOSS21 and GridBOSS form a fully integrated energy management platform that replaces the external breakers, transfer switches, generator controls, AC coupling hardware, and smart load controllers that competing system designs require as separate components. The result is a simpler installation, a cleaner permit package, lower material costs, and faster commissioning — without sacrificing any functionality.

250A Battery Charger — Fast Charging with Closed-Loop BMS Communication

The FlexBOSS21's 250A integrated battery charger replenishes 48V battery banks rapidly from solar, grid, or generator sources. RS485 and CANBus closed-loop BMS communication enables direct interoperability with EG4's own battery line and a wide range of third-party lithium battery brands — providing chemistry-aware charging that maximizes battery performance, accuracy of state-of-charge reporting, and long-term cycle life. Open-loop mode supports any 48V battery chemistry for maximum compatibility.

AUX Terminals with Generator Auto-Start

Dedicated AUX terminals support fully automatic generator start and stop based on configurable battery state-of-charge thresholds — no external relay or generator controller required. When battery reserves drop below your set minimum, the FlexBOSS21 signals the generator to start, charges the battery, and shuts the generator down once the target SOC is reached. Hands-free, fully automated generator management is standard equipment.

Multiple Operating Modes — Grid-Tie, Off-Grid, Zero Export, TOU, Self-Consumption

The FlexBOSS21 supports the full range of operating modes required for modern residential energy management: self-consumption mode prioritizes solar and battery over grid power; zero export mode prevents any energy from flowing back to the grid for utility-compliant installations; Time-of-Use (TOU) programming charges during cheap off-peak hours and dispatches during expensive peak periods; force discharge mode dispatches stored energy on demand; and full off-grid mode operates entirely independently from the grid. All modes are accessible and adjustable remotely through EG4's monitoring platform.

Advanced Grid Certifications — California, IEEE, and CSA Compliant

The FlexBOSS21 carries UL 1741 SA and SB certifications, California Rule 21 Phase I/II/III compliance, and CSA C22.2.107.1:2016 listing — covering the most stringent utility interconnection requirements in the United States and Canada. When paired with EG4 WallMount batteries, the system achieves UL 9540 certification as a complete energy storage system, satisfying AHJ listing requirements for battery storage installations across U.S. permit jurisdictions.

Scalable to 256kW — Up to 16 Units in Parallel

For large estates, farms, or light commercial properties requiring output beyond 16kW, up to 16 FlexBOSS21 units can be connected in parallel for a combined continuous output of 256kW with solar present — all within the same firmware, monitoring platform, and installation ecosystem.

Wi-Fi Monitoring, Mobile Alerts, and Remote Configuration

Built-in Wi-Fi connectivity delivers real-time system monitoring and remote configuration through the EG4 app and web portal — accessible from any smartphone or browser. Track solar production, battery state-of-charge, grid import/export, load consumption, and system health from anywhere. Adjust operating modes, set TOU schedules, and update firmware without a site visit.

10-Year Warranty

The FlexBOSS21 is backed by a 10-year full parts and product replacement warranty, registered within the first year of purchase from an authorized EG4 distributor.