Fortress Power Envy Duo 21 Hybrid Inverter – 21kW PV Whole-Home Energy Solution

Fortress Power Envy Duo 21 Hybrid Inverter

This inverter can only ship via freight truck. It can NOT ship via UPS or USPS. Please email us or give us a call if you have any questions.

The Fortress Power Envy Duo 21 is a powerful, split-phase hybrid inverter engineered for whole-home and light commercial solar + storage applications. Delivering 12 kW of continuous output and up to 16 kW of max export power, the Envy Duo 21 provides reliable energy for large homes, businesses, and critical-load backup systems.

This inverter integrates seamlessly with new or existing solar arrays. It is optimized for pairing with Fortress Power LiFePO₄ batteries, ensuring maximum performance, safety, and longevity. A 25 kW maximum PV input with multiple MPPT trackers gives system designers flexibility for rooftop, ground-mount, or mixed solar arrays

Certified to UL 1741-SA and IEEE 1547, the Envy Duo 21 is grid-compliant across the U.S. and built with advanced safety features. Smart system controls allow for time-of-use optimization, peak shaving, generator integration, and remote monitoring, making it an ideal choice for both grid-connected and off-grid solar storage systems.

Key Features:

• 12 kW continuous output / 16 kW surge capacity
• Split-phase design (120/240V) for residential & commercial use
• Optimized for Fortress Power LiFePO₄ batteries
• 25 kW PV input capacity with multiple MPPTs
• Advanced energy management: peak shaving, TOU shifting, zero export
• Remote monitoring & smart controls
• UL 1741-SA, IEEE 1547, and Rule 21 compliant

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

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

Back 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

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
• Display Touch color screen
• Communication interface Rs485/ Wi-Fi/ CAN