Fortress Power Envy Duo 21 Inverter

Name: Fortress Power Envy Duo 21 Inverter
Brand: Fortress Power
SKU: Envy Duo 21
Price: 5449.0 USD
Availability: InStock

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Fortress Power

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Envy Duo 21

$5,449.00

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Fortress Power Envy Duo 21 Inverter | 25kW PV Input | 12kW Continuous Output | Dual-Phase Compatible

Maximum Power. Dual-Purpose Design. Built for What’s Next.

The Fortress Power Envy Duo 21 is a high-output 48V hybrid inverter designed for advanced residential and light commercial energy systems. With up to 25kW of solar PV input, dual-phase compatibility, and seamless integration with Fortress Power’s 48V battery lineup, it delivers powerful performance for whole-home backup and intelligent energy management.

Supporting both 240V split-phase and 208V three-phase systems (when installed in parallel), the Envy Duo 21 provides 12kW continuous output and up to 16kW peak export—making it ideal for large residential systems, small businesses, and scalable energy installations.

Key Features

Massive PV Input Capacity:
- Supports up to 25kW of solar PV input
- Allows large solar arrays to operate at full potential
- Ideal for high energy demand properties
Dual Voltage Compatibility:
- Supports 240V split-phase residential systems
- Compatible with 208V three-phase commercial installations
- Three-phase requires two or more inverters in parallel
Whole-Home Backup with Fortress Batteries:
- Works with Fortress Power 48V batteries (eVault MAX, eFlex MAX, eForce)
- 12kW continuous output
- Up to 16kW export power
- Reliable backup for appliances, HVAC systems, and essential loads
Scalable System Design:
- Parallel up to 10 Envy Duo 21 inverters
- Up to 120kW total AC output
- Ideal for large homes, microgrids, and light commercial projects
Installer-Friendly Built-In Hardware:
- Integrated AC/DC breakers
- Built-in rapid shutdown transmitter
- Helps ensure NEC 2017/2020 compliance
- Reduces installation time and external components
Smart Monitoring & Remote Updates:
- Monitor solar, battery, and grid performance in real time
- Access historical system analytics
- Perform remote firmware updates through the Fortress Power mobile app

Applications

Large residential solar + storage systems
Light commercial buildings
Off-grid and grid-tied backup systems
Net metering and load shifting
Time-of-use optimization and zero-export configurations
Virtual Power Plant (VPP) participation

What’s Included

1 × Fortress Power Envy Duo 21 Hybrid Inverter
Integrated AC & DC Breakers
Built-in Rapid Shutdown Transmitter
Mounting Hardware
Fortress Power Mobile App Access
User Manual & Warranty Card

Requires a minimum of two inverters for 208V three-phase applications.

Specification Sheets:

Fortress Power Envy Duo 21 Inverter Specifications (PDF)

Manuals:

Fortress Power Envy Duo 21 Inverter Installation Guide & Owner Manual (PDF)

Specifications

Parameter	Details
Number of MPPT	3
Inputs per MPPT	2:2:1
Max Usable Input Current	26A / 26A / 15A
Max Short Circuit Input Current	31A / 31A / 19A
Start Input Voltage	100V
MPPT DC Nominal Voltage	360V
DC Voltage Range	100–550V
MPPT Operating Voltage Range	120–440V
Max PV Power	21,000W
Max PV Array Power	25,000W
Backup Nominal Output Current	50A @240V, 57.7A @208V
Backup Nominal Output Voltage	120/240V, 120/208V
Continuous Output Power	12,000VA @240V, 12,000VA @208V
Operating Frequency	50 / 60 Hz
Peak Power	2×Pn (0.5s)
THDV	<3%
Switching Time	<20 ms
Paralleling Capability	Up to 10 units (120kW)
Dimensions	22.3 × 35.2 × 11.2 in (566 × 893 × 285 mm)
Weight	125.71 lbs (57 kg)
Protection Rating	NEMA 4X / IP66
Cooling	Smart Cooling Fans
Topology	High Frequency Transformer-less
Relative Humidity	0–100%
Max Operating Altitude	<6561 ft (<2000 m)
Operating Temperature Range	-25°C to 60°C (>40°C derating)
Noise Emission	<67 dB
Idle Consumption	60W (average)
Display	Touch Color Screen
Communication Interface	RS485 / Wi-Fi / CAN
Max Grid Output Current with PV	66.7A
Max Grid Output Power with PV	16,000W @240V / 13,800W @208V
Continuous Output with Battery Only	12,000W @240V / 12,000W @208V
Rated Grid Voltage	120/240V, 120/208V
Operating Voltage Range	180–270V
Operating Frequency Range	55–65 Hz
Power Factor	0.99 @ full load
Reactive Power Adjustment	-0.8 to +0.8 leading (adjustable)
THDI	<3%
Sync Inrush Current	35A
Max Efficiency PV → Grid	97.5%
Max Efficiency Battery → Grid	94%
CEC Efficiency	96.9%
Battery Type	Lithium Battery / No Battery
Max Battery Charge Current	250A
Max Battery Discharge Current	250A
Battery Nominal Voltage	48V
Battery Voltage Range	40–60V

Understanding Your Power Needs

Power Calculation Guide

Sizing Metric	Formula & Example
Energy Consumption (Wh)	Formula: Watts × Hours Example: 60W × 4 hrs = 240 Wh
Battery Capacity (Ah)	Formula: Watt-hours ÷ System Voltage (V) Example: 240 Wh ÷ 12V = 20 Ah
Inverter Size (W)	Formula: Total Watts × 1.25 (safety margin) Example: 300W × 1.25 = 375W → Use 400W inverter
Total Load Power (W)	Formula: Sum of all appliance watts used simultaneously Example: Light (10W) + Fan (75W) = 85W
Runtime (hrs) of Battery	Formula: (Battery Ah × Voltage) ÷ Total Load (W) Example: (100Ah × 12V) ÷ 240W = 5 hrs

Find Your Power Match

Need / Application	System Recommendation
Basic lighting + phone charging	Recommended Battery: 50Ah – 100Ah (12V) Inverter Size: 100W – 200W Notes: For small backup setups
Home office (laptop, fan, TV)	Recommended Battery: 150Ah – 200Ah (12V or 24V) Inverter Size: 500W – 1000W Notes: For moderate usage with 4–6 hours of backup
Home backup (fridge, lights)	Recommended Battery: 200Ah+ (24V or 48V recommended) Inverter Size: 1000W – 1500W Notes: Ideal for longer backups or heavier loads
Business / shop power backup	Recommended Battery: 300Ah+ (48V system) Inverter Size: 2000W – 3000W Notes: Suitable for commercial setups or extended power outages

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Built for Energy Independence: Whether powering a cabin, prepping for emergencies, or going off-grid, our products are chosen for performance, reliability, and sustainability.

Fortress Power Envy Duo 21 Inverter

$5,449.00

Fortress Power Envy Duo 21 Inverter

Fortress Power

Envy Duo 21

#1 Authorized Fortress Power Distributor

Free Shipping + No Sales Tax

Hassle-Free Returns & Exchanges

Talk To A Real Person

Fortress Power Envy Duo 21 Inverter | 25kW PV Input | 12kW Continuous Output | Dual-Phase Compatible

Key Features

Applications

What’s Included

Specification Sheets:

Manuals:

Fortress Power Envy Duo 21 Inverter

Get In Touch:

Company Information:

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Company Information:

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