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Fortress Power Envy Duo 21-US > 16,000 Watt 48V High Capacity Hybrid Inverter
Fortress Power Envy Duo 21-US > 16,000 Watt 48V High Capacity Hybrid Inverter
 
Our Price: $5,669.00
Warranty: 10 Years / Lead Acid or Fortress Lithium Batteries Only


Availability: Pre-Order Available. Expected to ship September 2025.
Product Code: FORTRESS-ENVY-DUO-21-US-16KW
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Description Datasheet
 

Fortress Power > 16kW 48V High Capacity Hybrid Inverter | 240V split-phase, 208V three-phase

Manufacturer Part Number: Envy Duo 21-US (16kW)

Whole Home Solar hybrid inverter; Max 16KW ongrid and 12KW off-grid continous output;Max 21KW PV array; 200A transfer switch: IP 65 outdoor rated; pre-built AC &DC breakers; Built-in Apsmart RSD transmitter; 120/240V Single and split phase, 120/208V three phase, 127/220V single & split phase; 50/60HZ; breakers included

HIGH CAPACITY HYBRID INVERTER ENGINEERED
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 confi gurations, 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.

Specifications

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) 21,000
Max. PV ARRAY POWER (W) 25,000
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
THDV <3%
THDV <3%
Switching Time (ms) <20
AC Grid Output Data
Max. Output Current with pv (A) 66.7
Max. Output Power with pv (W) 16000 @ 240V, 13800 @ 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 leading adjustable
THDI <3%
Sync inrush current (A) 35
General Data
Paralleling Capability Up to 10 units (120kW)
Dimensions (W x H x D) 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
Efficiency
Max. EFFICIENCY PV to grid 97.50%
Max. EFFICIENCY battery to grid 94%
CEC Efficiency 96.9%
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
Altitude Limitation Performance
0 - 6561.68 feet (0-2000M) 12kW
6561.68 - 9842.52 feet (2000-3000M) 10.2kW
9842.52 - 13,123.36 feet (3000-4000M) 8.4kW
<13,123.36 feet (<4000M) Not Allowable
* Altitude Limitation performance include max charging, discharging, active power and backup output kW.

Safety Standards and Certifications
Safety PV Reverse polarity protection; DC switch for each MPPT; Output over-voltage protection varistor; Output over current protection; PV Ground fault monitoring; Grid monitoring; Pole sensitive leakage current Monitoring unit; AFCI; RSD; SURGE PROTECTION DEVICE (SPD): TYPE III DC PV , TYPE II AC
Certifications RULE 21 PHASE I, II, III; HAWAII RULE 14H & HECO SRD-IEEE-1547.1:2020 Ed.2; IEEE 1547.1: 2020; IEEE 1547: 2018, IEEE2030.5; LUMA PR; UL1741SA, UL1741SB; UL1741: 2021 ED3 PCS CRD; UL9540 (eFlex, eVault Max); CSA C22.2#107.1; CSA C22.2#330; FCC PART 15, CLASS B
Warranty 10 Years / Lead Acid, Lithium Batteries or Fortress Lithium Batteries

Features

High Performance. Built for Growth.

  • Accepts up to 25kW of PV input—ideal for large residential or small commercial solar arrays seeking maximum generation potential.

  • Supports both 240V split-phase and 208V three-phase applications, making it flexible for a wide range of grid configurations.

  • Parallel up to 10 units for a total output of 120kW, expanding as energy demands grow without the need for complete system redesign.

  • Includes built-in AC/DC breakers and an integrated rapid shutdown transmitter for faster, code-compliant installations.

  • Pairs with Fortress Power 48V batteries to deliver 12kW of continuous power and up to 16kW peak, ensuring stable, whole-home or light commercial backup.

Applications

  • Backup
  • Off-Grid
  • Zero Export
  • Time-of-Use
  • Net Metering
  • Virtual Power Plant
  • Smart Load
  • Peak Shaving
  • Microgrid

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