Description
Fortress Power Envy Duo 21 — a high-capacity 48V hybrid inverter engineered to dominate larger residential and light commercial solar-plus-storage installations.
Key Features:
- Triple MPPT with Up to 25,000W Solar Input: Three independent MPPTs with a 21kW inverter capacity handle large-scale arrays with maximum energy harvest efficiency.
- Dual-Phase Compatibility — 240V Split-Phase and 208V Three-Phase: Delivers 12kW of continuous backup output across both configurations, with up to 16kW max export power.
- Parallel Scalability Up to 120kW: Stack up to 10 units to grow your system capacity without a complete redesign, future-proofing every installation.
- Integrated AC/DC Breakers with Built-In Rapid Shutdown Transmitter: Factory-installed safety components streamline installation and ensure full code compliance out of the box.
- 250A Max Charge and Discharge with <20ms Switching Time: Paired with Fortress Power 48V batteries, the Envy Duo 21 delivers seamless, high-current backup with near-instant transfer.
The Fortress Power Envy Duo 21 sets a new benchmark for hybrid inverter performance in demanding energy environments. With a transformer-less high-frequency topology and 97.5% peak PV-to-grid efficiency, this inverter converts and delivers power with exceptional precision and minimal loss.
Purpose-built for versatility, the Envy Duo 21 supports backup, off-grid, zero export, time-of-use, net metering, virtual power plant, peak shaving, smart load, and microgrid applications — all within one powerful wall-mounted cabinet. The intuitive touch color display and full Wi-Fi, RS485, and CAN connectivity deliver complete real-time visibility and remote control from anywhere.
Rated for operation from -25°C to 60°C with IP66 and NEMA4X weatherproofing, the Envy Duo 21 is engineered to perform in the harshest conditions. Backed by a 10-year standard warranty and a full suite of certifications including UL1741SA, UL1741SB, and Rule 21, this inverter is the definitive choice for installers and homeowners who refuse to settle.
Technical Specifications
| Specification | FP-ENVY DUO 21 |
|---|---|
| PV INPUT | |
| Number of MPPTs | 3 |
| Inputs per MPPT | 2 / 2 / 1 |
| Max. Usable Input Current (A) | 26 / 26 / 15 |
| Max. Short Circuit Input Current (A) | 31 / 31 / 19 |
| Start Input Voltage (V) | 100 |
| MPPT DC Nominal Voltage (V) | 360 |
| DC Voltage Range (V) | 100–550 |
| MPPT Operating Voltage Range (V) | 120–440 |
| Max. Inverter Power (W) | 21,000 |
| Max. PV Array Power (W) | 25,000 |
| AC GRID OUTPUT | |
| Max. Output Current with PV (A) | 66.7 |
| Max. Output Power with PV (W) | 16,000 @ 240V / 13,800 @ 208V |
| Continuous Power Output — Battery Only (W) | 12,000 @ 240V / 12,000 @ 208V |
| Rated Voltage (V) | 120/240, 120/208 |
| Operating Voltage Range (V) | 180–270 |
| Operating Frequency (Hz) | 50/60 |
| Operating Frequency Range (Hz) | 55–65 |
| Power Factor | 0.99 @ Full Load |
| THDI | <3% |
| Sync Inrush Current (A) | 35 |
| BACKUP OUTPUT | |
| Nominal Output Current (A) | 50 @ 240V / 57.7 @ 208V |
| Nominal Output Voltage (V) | 120/240, 120/208 |
| Continuous Output Power (VA) | 12,000 @ 240V / 12,000 @ 208V |
| Peak Power (VA) | 2x Pn, 0.5s |
| Switching Time (ms) | <20 |
| THDV | <3% |
| EFFICIENCY | |
| Max. Efficiency PV to Grid | 97.5% |
| Max. Efficiency Battery to Grid | 94% |
| CEC Efficiency | 96.9% |
| BATTERY | |
| Compatible Battery Type | Lithium / No Battery |
| Nominal Battery Voltage (V) | 48 |
| Battery Voltage Range (V) | 40–60 |
| Max. Charge Current (A) | 250 |
| Max. Discharge Current (A) | 250 |
| GENERAL | |
| Dimensions (in) | 22.3 x 35.2 x 11.2 |
| Weight | 125.71 lbs |
| Degree of Protection | NEMA4X / IP66 |
| Cooling | Smart Cooling Fans |
| Topology | High Frequency Transformer-less |
| Operating Temperature | -25°C to 60°C (Derating >40°C) |
| Relative Humidity | 0–100% |
| Max. Altitude | <6,561 ft (<2,000 m) |
| Noise Emission | <67 dB |
| Idle Consumption (W) | 60 |
| Display | Touch Color Screen |
| Communication | RS485 / Wi-Fi / CAN |
| Paralleling Capability | Up to 10 Units (120kW) |
| AFCI | Yes |
| RSD | Yes |
| Standard Warranty | 10 Years |
Specs & Info