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The Envy Duo 21 is Fortress Power’s most powerful 48V hybrid inverter, built to handle both residential and light commercial energy needs. With up to 25kW solar input and dual-phase support (240V split-phase and 208V three-phase), it delivers a reliable 12kW of continuous backup power with up to 16kW export capacity.
Perfectly paired with Fortress Power’s 48V batteries, the Envy Duo 21 offers flexible applications from whole-home backup to off-grid living. With built-in AC/DC breakers, rapid shutdown transmitter, and scalability up to 120kW, it’s a future-ready solution designed for maximum performance and long-term reliability.
Envy Duo 21 Installation Manual
| PV Output Data | |
| Number of MPPT | 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. Power (W) | 21000 |
| Max. PV ARRAY POWER (W) | 25000 |
| Backup Output Data | |
| Nominal output current (A) | 50@240V, 57.7@208V |
| Nominal output voltage (V) | (120/240), (120/208) |
| Continuous output power (VA) | 12000@240V, 12000@208V |
| Operating frequency (Hz) | 60 & 50 |
| Peak power (VA) | 2xPn, 0.5s |
| THDV | <3% |
| Switching Time (ms) | <20 |
| General Data | |
| Paralleling Capabiliy | Up to 10 units (120kW) |
| Dimensions | 22.3 x 35.2 x 11.2 in (566 x 893 x 285 mm) |
| Weight | 125.71 lbs (57 kg) |
| Degree of protection | NEMA4X / IP66 |
| Cooling concept | Smart Cooling Fans |
| Topology | High Frequency Transformer-less |
| Relative humidity | 0-100% |
| Altitude (m) | <6561ft. (<2000m) |
| Operating Temperature Range (ºC) | -25~60>40 Derating |
| Noise emission (dB) | <67 |
| Idle Consumption AVG (W) | 60 |
| Display | Touch color screen |
| Communication interface | Rs485/ Wi-Fi/ CAN |
| AC Grid Output Data | |
| Max. Output Current with pv (A) | 66.7 |
| Max. Output Power with pv (W) | 16000@240V 13800@208V |
| Continuous power output with battery only (W) | 12000@240V, 12000@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 |
| Reactive power adjust range | -0.8~+0.8 leadingAdjustable |
| THDI | <3% |
| Sync inrush current (A) | 35 |
| Efficiency | |
| Max. EFFICIENCY PV to grid | 97.50% |
| Max. EFFICIENCY battery to grid | 94% |
| CEC Efficiency | 96.90% |
| Battery Data | |
| Type | Lithium battery/ No Battery |
| Max. charge current (A) | 250 |
| Max. discharge current (A) | 250 |
| Nominal voltage (V) | 48 |
| Voltage range (V) | 40-60 |
Ships within 48 hours · Estimated delivery Jun 30 - Jul 5
US$40
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