Fortress Power Envy Duo 21

Power larger solar + storage systems with the Fortress Power Envy Duo 21, a high-capacity 48V hybrid inverter built for demanding residential and light commercial energy needs. With up to 25kW PV input, dual-voltage compatibility (240V split-phase / 208V three-phase), and scalable paralleling up to 120kW, it’s a future-ready solution for backup power, off-grid setups, zero-export, TOU optimization, and more.

Key Features & Benefits:

• High PV input capacity: Supports up to 25kW PV array power for larger residential or light commercial solar arrays

• Dual voltage compatibility: Works with 120/240V split-phase and 120/208V three-phase configurations

• Reliable backup output: 12,000W continuous backup power (240V or 208V) with <20ms switching time

• Higher grid output with PV: Up to 16,000W @ 240V (or 13,800W @ 208V) when PV is available

• Seamless battery integration: Designed to pair with Fortress Power 48V batteries (40–60V range) for stable backup performance

• Scalable system design: Parallel up to 10 units (120kW total) to expand as energy demands grow

• Install-friendly, code-compliant hardware: Built-in AC/DC breakers + integrated rapid shutdown transmitter

• Remote monitoring + updates: Monitor production/consumption and perform remote firmware updates via Fortress Power mobile app (where supported)

• Built for tough environments: NEMA 4X / IP66 enclosure, smart cooling fans, and touch color display

Quick Specs:

• MPPTs: 3 (inputs per MPPT: 2:2:1)

• Max PV Array Power: 25,000W | Max PV Power: 21,000W

• Continuous Output (Battery Only): 12,000W @ 240V or 208V

• Max Output w/ PV: 16,000W @ 240V | 13,800W @ 208V

• Efficiency: 97.5% max PV-to-grid | 96.9% CEC

• Comms: RS485 / Wi-Fi / CAN

• Size / Weight: 22.3 x 35.2 x 11.2 in | 125.71 lb

• Warranty: 10 Years

What’s in the Box (Unboxing):

• 1 x Envy inverter with hole knockout caps 

• 1 x Wall mount bracket

• 2 x L-shaped braces

• 1 x Battery RJ45 adapter

• 1 x Installation/User manual

• 2 x Current transformers (CT) (connected by one cable)

• 1 x Dongle

• 2 x Battery-to-inverter comm cable + inverter-to-inverter comm cable

• 4 x RJ45 terminals

• 6 x Mounting screws (wood)

• 6 x expansion screws

• 4 x Cross head screws: L-brace + dongle

• 1 x Knockout hole template

User Manual / Documents:

• Fortress Power Envy Duo 21 Hybrid Inverter Data Sheet
  
• Fortress Power Envy Duo 21 Hybrid Inverter Installation Manual
• Fortress Power Envy Duo 21 Hybrid Inverter Warranty