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
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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
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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:
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 | 48V | 25kW PV Input | 12kW Backup | 240V Split-Phase & 208V 3-Phase | Parallel to 120kW | 10-Year Warranty
- Regular price
- $5,759.54
- Sale price
- $5,759.54
- Regular price
-
$7,200.00
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Fortress Power Envy Duo 21 Hybrid Inverter | 48V | 25kW PV Input | 12kW Backup | 240V Split-Phase & 208V 3-Phase | Parallel to 120kW | 10-Year Warranty
Testimonials
50,000+ Happy Customers
Join thousands of happy customers who made the switch to solar.
"Amazing experience from start to finish. The team was incredibly helpful and the system is performing beyond expectations. Couldn't be happier with our decision."
"The whole process was seamless. From ordering to installation, everything was straightforward. Our electricity bill has dropped significantly!"
"Best investment we've made for our home. The customer support is outstanding — they walked us through every step of the setup process."
"We compared prices everywhere and this was by far the best deal. The quality of the panels is top-notch and installation guidance was superb."
"Great product and even better customer service. They helped us design the perfect system for our needs. Highly recommend to anyone considering solar."
"From the free proposal to the final install, everything exceeded our expectations. We're producing more energy than we consume most months!"
"Amazing experience from start to finish. The team was incredibly helpful and the system is performing beyond expectations. Couldn't be happier with our decision."
"The whole process was seamless. From ordering to installation, everything was straightforward. Our electricity bill has dropped significantly!"
"Best investment we've made for our home. The customer support is outstanding — they walked us through every step of the setup process."
"We compared prices everywhere and this was by far the best deal. The quality of the panels is top-notch and installation guidance was superb."
"Great product and even better customer service. They helped us design the perfect system for our needs. Highly recommend to anyone considering solar."
"From the free proposal to the final install, everything exceeded our expectations. We're producing more energy than we consume most months!"
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Frequently Asked Questions
Find the answers to some of the most common questions customers have before placing their order.
Yes. Our team can help you choose the right solar kit based on your goals, power needs, and location. We provide personalized guidance before and after your purchase at no additional cost.
Many of our customers complete the majority of installation themselves using our diagrams and support resources. For final electrical connections, a licensed electrician may be required depending on local codes.
While we do not directly install systems, we can help connect you with qualified local professionals and provide technical documentation to support your installer.
We stand behind our products. If you have specific questions about returns, eligibility, or specific product conditions, you can learn more in our help center linked below.
All components are backed by manufacturer warranties. In addition, our team provides free lifetime technical support to assist you throughout the life of your system.
Yes! We offer a variety of flexible payment plans to fit any budget. Options include monthly financing with competitive interest rates, and some plans require no money down. Apply during checkout and get approved in minutes.
If you're ready to place your order, you can go ahead and checkout online right now. If you have questions, our friendly team of solar experts are happy to assist and can take your order over the phone. If you're interested in financing, you will find the application at checkout online. So whatever is best for you, we are happy to accommodate.
Our team works hard to process all orders within 24-48 hours. Most products ship directly to your door using the quickest, most cost effective ground shipping services depending on size. You’ll receive tracking details and delivery coordination as soon as your order ships. Our average shipping times are anywhere from 3-7 days.
You’ll have direct access to our support team via phone, email, and chat. Whether it’s setup guidance or troubleshooting years down the road, we’re here to help.
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