Description
Fortress Power Envy 16kW Duo 21 Whole Home Solar Hybrid Inverter Envy Duo 21-US (16kW)
Compatible products:
Fortress eFlex Max 5.4 kWh 51.2V Battery
Fortress Power 16kWh eBoost LFP Battery
Unmatched power and versatility for residential and commercial solar applications.
The Fortress Power Envy Duo 21 is a next-generation hybrid inverter engineered to handle whole-home energy needs with built-in reliability, scalability, and advanced safety features. Whether you’re on-grid, off-grid, or using a hybrid setup, this inverter delivers exceptional performance in all conditions.
Key Benefits
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Massive Power Handling – Supports up to 16kW continuous on-grid output and 12kW continuous off-grid output.
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High PV Input Capacity – Connect up to a 21kW solar PV array for maximum energy harvest.
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Whole-Home Backup – Built-in 200A transfer switch seamlessly powers critical and non-critical loads during outages.
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Flexible Voltage & Phases – Compatible with 120/240V single & split phase, 120/208V three phase, and 127/220V single & split phase at 50/60Hz.
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Outdoor-Ready – Rugged IP65 weatherproof rating ensures safe installation indoors or outdoors.
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Pre-Configured Safety – Comes with pre-built AC & DC breakers included for streamlined installation.
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Built-in RSD Compliance – Equipped with an APsmart rapid shutdown transmitter for NEC 690.12 compliance.
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Smart Design – Pre-integrated components reduce install time and simplify system wiring.
Special Technology
3× MPPT Architecture: Inputs per tracker (2:2:1) with wide 100–550 V DC range enable flexible stringing.
Fast Transfer:<20 ms switchover helps keep critical loads online during grid events.
Advanced Protection: AFCI, RSD, PV ground-fault monitoring, surge protection (DC Type III / AC Type II), anti-islanding.
Warranty
10-Year Manufacturer Warranty.
Best Uses
Whole-Home Backup & TOU Shifting: Seamless PV + battery operation with generator-ready capability.
Light Commercial / Microgrids: Parallel stacks up to 120 kW with flexible 208/240 V deployments.
Specifications Table
| Specification | Data |
|---|---|
| Model | Envy Duo 21-US (16 kW) |
| PV Max / Recommended Max | 25,000 W / 21,000 W |
| MPPTs / Inputs per MPPT | 3 / 2:2:1 |
| DC Voltage Range / MPPT Range | 100–550 Vdc / 120–440 Vdc |
| Start Voltage / MPPT Nominal | 100 Vdc / 360 Vdc |
| Max Usable Input Current (A) | 26 / 26 / 15 |
| Max Short-Circuit Current (A) | 31 / 31 / 19 |
| AC Grid Output | |
| Grid Voltages | 120/240 Vac split-phase; 120/208 Vac 3-phase |
| Max Output Power with PV | 16,000 W @ 240 V; 13,800 W @ 208 V |
| Continuous (Battery-Only) | 12,000 W @ 240 V / 208 V |
| Max Output Current (PV assist) | 66.7 A |
| Frequency / Range | 50/60 Hz / 55–65 Hz |
| Power Factor / THDi | 0.99 @ full load / <3% |
| Backup Output | |
| Nominal Output | 120/240 V or 120/208 V |
| Continuous Power / Peak | 12,000 VA / 2× Pn for 0.5 s |
| Switching Time | <20 ms |
| THDv | <3% |
| Efficiency | |
| PV→Grid / Battery→Grid | 97.5% / 94% |
| CEC Weighted | 96.9% |
| Battery | |
| Nominal / Range | 48 V / 40–60 V |
| Max Charge / Discharge Current | 250 A / 250 A |
| General | |
| Paralleling | Up to 10 units (120 kW total) |
| Enclosure | NEMA 4X / IP66 |
| Dimensions (W × H × D) | 22.3 × 35.2 × 11.2 in |
| Weight | 125.71 lb |
| Cooling | Smart cooling fans |
| Operating Temp | −25 °C to +60 °C (derate >40 °C) |
| Altitude / Humidity | < 6561 ft (2000 m) / 0–100% RH |
| Noise | < 67 dB |
| Idle Consumption | ~60 W |
| Display / Comms | Touch color screen / RS485, Wi-Fi, CAN |
| Safety & Certifications | AFCI, RSD, GFDI; UL1741 SA/SB, UL9540 (with Fortress batteries), IEEE 1547/1547.1, Rule 21, HECO 14H, FCC Part 15 Class B |
| Warranty | 10 Years |
About Fortress:
Why Buy From US Solar Supplier?
As an American founded company out of Kentucky, US Solar Supplier is committed to providing top-quality solar products, backed by the world’s leading manufacturers. Our promise is to get you the fairest price from the best brands that offer warranties you can count on.
We update our inventory daily with solar components that feature the latest technology. With a reputation for excellence and a dedication to customer satisfaction, we ensure that every product we sell meets the highest standards in the industry.
Need Assistance?
We’re here to help! If you have any questions or need more information before making your purchase, don’t hesitate to call us at 1-800-230-7004. Our knowledgeable and friendly team is ready to assist you with product details, installation advice, or the purchasing process.
Why Buy From Us?
Trusted Supplier: We work with Tier 1 manufacturers who stand behind their products.
Expert Support: Our team is here to guide you every step of the way.
Manufacturer-Backed Warranties: Enjoy peace of mind with the 10-year product warranty directly from the manufacturer.
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Join the many satisfied customers who have trusted us for their solar needs. Add to your cart now to secure your high-efficiency solar panels and take the next step towards sustainable energy!
FAQs
Q: Is the Envy Duo 21-US compatible with my solar panels?
Yes, the Envy Duo 21-US is designed to work with a wide range of solar panels. Your installer will configure the system to ensure maximum compatibility and efficiency.
Q: Do I need a battery to use the Envy Duo 21-US?
No, a battery is not required. The inverter can operate as a standard grid-tied unit. However, pairing it with a battery allows energy storage for nighttime use or backup power during outages.
Q: How do I monitor the performance of my Envy Duo 21-US?
The inverter connects via Wi-Fi or Ethernet to a monitoring platform or app. This lets you track energy production, consumption, and battery performance in real time.
Q: What happens if there is a power outage?
If a battery is installed and configured for backup, the inverter provides seamless power to selected circuits during outages. Without a battery, the inverter will shut down in accordance with grid safety regulations.
Q: How do I maintain the Envy Duo 21-US?
Maintenance is minimal. You should periodically check for error messages, ensure the inverter has proper ventilation, and follow any inspection schedule recommended by your installer.
Q: What is the efficiency of the Envy Duo 21-US (16KW)?
The inverter offers high conversion efficiency. For exact specifications, including peak efficiency ratings, refer to the official Envy Duo datasheet.
Q: What are the input and output voltage ranges?
The Envy Duo 21-US typically supports residential split-phase 120/240V operation. For detailed DC input voltage ranges and AC output parameters, consult the official documentation.
Q: What communication protocols does the Envy Duo 21-US use?
It supports Wi-Fi, Ethernet, and may include additional communication interfaces (e.g., RS485, Modbus) for system integration and smart energy management.
