Envy Duo 21 Inverter
A high-capacity hybrid inverter engineered for larger solar + storage systems.
Coming Q4 of 2025!
Envy Duo 21 Inverter
Maximum Power. Dual-Purpose Design.
The Fortress Power Envy Duo 21 is a powerful 48V hybrid inverter designed to handle demanding residential and light commercial energy needs. With a maximum PV input of 25kW and dual-phase compatibility (240V split-phase and 208V three-phase), it delivers 12kW of continuous output power across both configurations, with peak outputs of 16kW (240V) and 13.8kW (208V).
Perfectly matched with Fortress Power’s 48V battery systems, the Envy Duo 21 supports multiple applications. Its integrated AC/DC breakers, rapid shutdown transmitter, and parallel scalability up to 120kW make it a versatile, future-ready solution.
Applications
Residential
Commercial
FEATURES
PRODUCT INFORMATION
| 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 |
| 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 |
VIDEO LIBRARY
Video Library Coming Soon
PRODUCT COMPATIBILITY
FREEDOM OF CHOICE WITH OUR ENVY INVERTERS!
Our Envy inverters are battery-agnostic!
What does this mean for you? It means you get to choose the battery that aligns with your vision. Our inverters seamlessly integrate with a wide range of lithium batteries. We have compiled a list of all the battery manufacturers you can choose from!
Info Sheet
Download Here
Monitor and control your Envy Inverter Anywhere and Anytime!
✅ Monitor Performance of Each Battery
✅ Update Firmware Over The Air
✅ Participate in Virtual Power Plant Programs
