$4,898.00
Fortress Power Envy Duo 21 Whole Home 21kW Solar Hybrid Split Phase Inverter—
$4,898.00
The Story
Fortress Power Envy Duo 21 Whole Home 21kW Solar Hybrid Split Phase Inverter
Description
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 configurations, 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.
Applications
- Modern Households with Growing Energy Needs
- Light Commercial Properties
- Hybrid and Off-Grid Living
- DIY Solar Setup
Product Specifications
Fortress Power Envy Duo 21 Whole Home 21kW Solar Hybrid Split Phase Inverter Product 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) | 21000 |
| Max. PV ARRAY POWER (W) | 25000 |
| 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 |
| Peak power (VA) | 2xPn, 0.5s |
| THDV | <3% |
| Switching Time (ms) | <20 |
| 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 |
| 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 |
| 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 |
| Power Factor | 0.99@full load |
| Reactive power adjust range | -0.8~+0.8 leadingAdjustable |
| THDI | <3% |
| Sync inrush current (A) | 35 |
| Efficiency | |
| Max. EFFICIENCY PV to grid | 97.50% |
| Max. EFFICIENCY battery to grid | 94% |
| CEC Efficiency | 96.90% |
| 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 |
Diagram
Product Manual
Data Sheet
Product Warranty
Fortress Power Envy Duo 21 Warranty
10 Years / Lead Acid, Lithium Batteries or Fortress Lithium Batteries
Product FAQs
Fortress Power Product FAQs
1) Does energy storage work well with my solar system?
Yes. On the grid? Absolutely! Energy storage adds a lot of value to your solar systems. It keeps your solar system operating when your utility service is interrupted. Without energy storage, your PV system will be forced to shutdown when the grid is off.
If you live off grid, energy storage enables you to use the clean solar energy to power your home day and night.
Fortress Power also knows you’re a fan of conservation—energy storage saves both your surplus solar energy and your cash since it reduces on grid energy dependence.
2) Can I use energy storage without solar panels?
Absolutely. For on grid clients, a home energy storage unit stores energy from your electricity provider. If an outage occurs, home energy storage can provide up to 24 hours of potentially life-saving power. Need more reassurance? Fortress Power offers batteries with larger storage capabilities, completely customizable to your needs. And, like you, we appreciate saving money. When electricity is at its lowest daily rate, our smart energy storage units use that period to charge. When peak electric use occurs, our energy storage units can discharge power to suit your lifestyle.
3) What about power outage protection?
Power interruptions shouldn’t disrupt your schedule. An energy storage system will keep your solar system operating during grid outages. When paired with solar panels, an energy storage system supplies unlimited energy delivery. The solar panels power your home during the day and use any excess power to charge the battery. At night, the system keeps your space bright. When used without solar panels, power outage support is dependent on battery size and your energy use. Batteries providing at least 12 hours of backup power are safest.
4) Are home energy storage systems financially beneficial?
You can use the energy storage to shelve your peak usage. When electricity is at its lowest daily rate, our smart energy storage uses that period to charge. During the peak periods, our energy storage system can power your home, reducing your electricity bill. Clients with solar panel installations enjoy a faster return on investment.
5) Do I receive incentives on my energy storage system?
If your energy storage is powered by solar panels, you are eligible for 30% federal tax credit. Many states and utilities provide rebates for homes and businesses with energy storage systems, aiming for grid resilience.
6) What is Lithium batteries lifespan?
We provide a 10 year product warranty and guarantee up-to 8000 cycles, whichever comes first. Speak to our representatives for details.
7) Why choose Lithium Iron Phosphate over Lithium Ion batteries?
We use Lithium Iron Phosphate (LiFePo4; Lithium Ferro Phosphate) technology – the safest lithium technology in the industry. It’s environmentally friendly and can be fully recycled. While Many other competitors, such as LG Chem, Tesla and Panasonic use cobalt-based Lithium-Ion battery, which has a very poor thermal stability. Any short circuit or cell-breakage can cause thermal runaway and catch fire.
And comparatively, Lithium Iron Phosphate battery deliver substantially higher amount of life cycles. We guarantee up-to 6000 cycles, while LG Chem, Tesla and Panasonic provide less than 3000 cycles.
8) Are Fortress Lithium batteries widely compatible?
Yes, our batteries are designed to work with all 48V chargers and hybrid inverters. We work well with Schneider, Outback, Magnum, Sol-Ark, Victron, Morningstar and so on. Please Check out our Inverter Compatibility list.
9) Are permits required for installation?
Legal requirements vary by location. Fortress Power’s technical support team will help you on obtaining permits.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Description
Fortress Power Envy Duo 21 Whole Home 21kW Solar Hybrid Split Phase Inverter
Description
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 configurations, 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.
Applications
- Modern Households with Growing Energy Needs
- Light Commercial Properties
- Hybrid and Off-Grid Living
- DIY Solar Setup
Product Specifications
Fortress Power Envy Duo 21 Whole Home 21kW Solar Hybrid Split Phase Inverter Product 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) | 21000 |
| Max. PV ARRAY POWER (W) | 25000 |
| 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 |
| Peak power (VA) | 2xPn, 0.5s |
| THDV | <3% |
| Switching Time (ms) | <20 |
| 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 |
| 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 |
| 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 |
| Power Factor | 0.99@full load |
| Reactive power adjust range | -0.8~+0.8 leadingAdjustable |
| THDI | <3% |
| Sync inrush current (A) | 35 |
| Efficiency | |
| Max. EFFICIENCY PV to grid | 97.50% |
| Max. EFFICIENCY battery to grid | 94% |
| CEC Efficiency | 96.90% |
| 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 |
Diagram
Product Manual
Data Sheet
Product Warranty
Fortress Power Envy Duo 21 Warranty
10 Years / Lead Acid, Lithium Batteries or Fortress Lithium Batteries
Product FAQs
Fortress Power Product FAQs
1) Does energy storage work well with my solar system?
Yes. On the grid? Absolutely! Energy storage adds a lot of value to your solar systems. It keeps your solar system operating when your utility service is interrupted. Without energy storage, your PV system will be forced to shutdown when the grid is off.
If you live off grid, energy storage enables you to use the clean solar energy to power your home day and night.
Fortress Power also knows you’re a fan of conservation—energy storage saves both your surplus solar energy and your cash since it reduces on grid energy dependence.
2) Can I use energy storage without solar panels?
Absolutely. For on grid clients, a home energy storage unit stores energy from your electricity provider. If an outage occurs, home energy storage can provide up to 24 hours of potentially life-saving power. Need more reassurance? Fortress Power offers batteries with larger storage capabilities, completely customizable to your needs. And, like you, we appreciate saving money. When electricity is at its lowest daily rate, our smart energy storage units use that period to charge. When peak electric use occurs, our energy storage units can discharge power to suit your lifestyle.
3) What about power outage protection?
Power interruptions shouldn’t disrupt your schedule. An energy storage system will keep your solar system operating during grid outages. When paired with solar panels, an energy storage system supplies unlimited energy delivery. The solar panels power your home during the day and use any excess power to charge the battery. At night, the system keeps your space bright. When used without solar panels, power outage support is dependent on battery size and your energy use. Batteries providing at least 12 hours of backup power are safest.
4) Are home energy storage systems financially beneficial?
You can use the energy storage to shelve your peak usage. When electricity is at its lowest daily rate, our smart energy storage uses that period to charge. During the peak periods, our energy storage system can power your home, reducing your electricity bill. Clients with solar panel installations enjoy a faster return on investment.
5) Do I receive incentives on my energy storage system?
If your energy storage is powered by solar panels, you are eligible for 30% federal tax credit. Many states and utilities provide rebates for homes and businesses with energy storage systems, aiming for grid resilience.
6) What is Lithium batteries lifespan?
We provide a 10 year product warranty and guarantee up-to 8000 cycles, whichever comes first. Speak to our representatives for details.
7) Why choose Lithium Iron Phosphate over Lithium Ion batteries?
We use Lithium Iron Phosphate (LiFePo4; Lithium Ferro Phosphate) technology – the safest lithium technology in the industry. It’s environmentally friendly and can be fully recycled. While Many other competitors, such as LG Chem, Tesla and Panasonic use cobalt-based Lithium-Ion battery, which has a very poor thermal stability. Any short circuit or cell-breakage can cause thermal runaway and catch fire.
And comparatively, Lithium Iron Phosphate battery deliver substantially higher amount of life cycles. We guarantee up-to 6000 cycles, while LG Chem, Tesla and Panasonic provide less than 3000 cycles.
8) Are Fortress Lithium batteries widely compatible?
Yes, our batteries are designed to work with all 48V chargers and hybrid inverters. We work well with Schneider, Outback, Magnum, Sol-Ark, Victron, Morningstar and so on. Please Check out our Inverter Compatibility list.
9) Are permits required for installation?
Legal requirements vary by location. Fortress Power’s technical support team will help you on obtaining permits.
