Quad Fortress Envy Duo 21 Hybrid Solar Kit | 48kW 120/240V | 36.8kW Solar | 128kWh Battery
Price range: $67,828.00 through $73,128.08
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A solar kit built around four Fortress Envy Duo 21 hybrid inverters.
- 48 kW continuous 120/240V split-phase output
- Solar: 92 × 400W panels (36.8 kW DC)
- Storage: 128 kWh (8 × 16 kWh Wall/Floor-Mount) Fortress eBoost 16 kWh LiFePO4 with eWay mounts
- Optional Tigo rapid shutdown or Tigo optimizers
- Exports solar where your utility allows
Racking sold separately.
Quad Fortress Envy Duo 21 Hybrid Solar Kit | 48kW 120/240V | 36.8kW Solar | 128kWh Battery
This kit is built around four Fortress Envy Duo 21 hybrid inverters, delivering 48 kW of continuous 120/240V split-phase output, paired with 92 × 400W panels (36.8 kW DC) and 128 kWh (8 × 16 kWh Wall/Floor-Mount) of storage.
- 48 kW continuous AC output, 120/240V split-phase
- Surge capacity up to 96 kW for motor starting
- Solar array: 92 × 400W panels (36.8 kW DC)
- Battery options: 128 kWh (8 × 16 kWh Wall/Floor-Mount) (Fortress eBoost 16 kWh LiFePO4 with eWay mounts)
- Exports solar where your utility allows
- Optional Tigo rapid shutdown or Tigo optimizers + rapid shutdown
Choose Your Configuration
| Battery Storage | 128 kWh (8 × 16 kWh Wall/Floor-Mount) Rack-Mount batteries install in a battery rack or cabinet; Wall/Floor-Mount batteries mount on a wall or stand on the floor. |
| Rapid Shutdown | None: includes PV disconnects Tigo Rapid Shutdown: TS4-A-F on every panel Tigo Optimizers + Rapid Shutdown: TS4-A-O on every panel plus Tigo CCA monitoring kit |
Options are offered in specific combinations; available combinations are shown in the selector above.
Rapid Shutdown or Optimizers?
| None (PV disconnects) | Best for ground-mounted arrays or other installations where module-level rapid shutdown isn’t required. Includes PV disconnects. |
| Tigo Rapid Shutdown | Required for most roof-mounted arrays on buildings (NEC 690.12). A TS4-A-F on each panel drops the array to a safe voltage within seconds when the system is shut off, protecting firefighters and service crews. |
| Tigo Optimizers + Rapid Shutdown | Everything rapid shutdown does, plus panel-level optimization and monitoring. Each TS4-A-O lets panels work independently, so shade, soiling or panels on different roof planes don’t drag down the whole string, and the Tigo CCA shows each panel’s output. |
Rapid shutdown requirements depend on the code adopted by your jurisdiction; confirm with your AHJ.
Estimated Annual Solar Production
| Phoenix, Arizona | ~62,600 (92P) kWh/year |
| Chicago, Illinois | ~46,400 (92P) kWh/year |
Planning estimates for an unshaded, south-facing array at about 30° tilt with typical losses. Actual production varies with location, orientation, tilt, shading, weather and equipment. Use a site-specific model before purchase.
System Overview
The kit pairs the inverter with an array sized to refill the battery on an average day (3.5 peak sun hours) and a battery bank that can deliver the inverter’s full output.
Ideal Applications
- Whole-home backup for very high-demand homes
- Off-grid homesteads with shops and multiple HVAC systems
- Large ranches and multi-building properties
What’s Included
- Four Fortress Envy Duo 21 hybrid inverter units
- ALEX-400 400W solar panels (count per configuration)
- Fortress eBoost 16 kWh LiFePO4 with eWay mounts (battery configurations), with mounting and battery cabling
- MC4 connector pairs and 10 AWG PV wire (black and red)
- PV disconnects (one per two strings) on configurations without rapid shutdown
- Tigo options: TS4-A-F rapid shutdown devices, or TS4-A-O optimizers with a Tigo CCA kit (plus Tigo TAPs on larger arrays)
| Weight | N/A |
|---|---|
| Dimensions | 72 × 48 × 54 in |
| Brand | |
| Inverter Platform | Fortress Envy Duo 21 |
| Inverter Quantity | Quad |
| Continuous Output | 48 kW |
| Inverter Size (KW) | 30kW+ |
| Output (V) | 120V/240V |
| Grid Connection | Grid-Interactive Hybrid (Can Export) |
| Generator Compatible | Yes |
| Inverter Type | All-in-one Inverter |
| Solar Capacity (DC) | 30kW+ |
| Battery Capacity (KWH) | 100kWh+ |
| Solar Array | 92 Panels (36.8 kW) |
| Battery Storage | 128 kWh |
| Rapid Shutdown | None, Tigo Optimizers + Rapid Shutdown, Tigo Rapid Shutdown |
What Can It Power?
Built around the Fortress Envy Duo 21, a hybrid inverter built around Fortress eBoost batteries and eWay mounts, this kit delivers 48 kW of continuous 120/240V split-phase output.
0.5–1.5 kW
Refrigerator and freezer, LED lights, ceiling fans, phone and laptop charging, modem, router and TV. These small and cycling loads are the starting point for long outage coverage.
1.5–5 kW each
Microwave, coffee maker, washer or dishwasher as needed. An electric water heater, dryer, oven or range can use a large share of the output, so stagger them instead of running them together.
Check starting current
A compatible mini-split, central HVAC, well pump or shop tool may run when its running demand and starting current fit within 48 kW continuous and 96 kW surge. Check the actual equipment; tonnage or horsepower alone doesn’t confirm it. A soft starter can help some compressors.
How Long Will It Run?
Battery size sets how much energy you have. These battery-only estimates use 80% of nominal storage delivered to loads (102.4 kWh from 128 kWh).
204.8 hrs
102.4 hrs
51.2 hrs
25.6 hrs
4.3 hrs
2.1 hrs
Runtime = usable battery energy ÷ average load, starting full, with no solar, grid or generator. Average load includes cycling: a 1 kW appliance running half the time averages about 0.5 kW. Actual results depend on settings, battery condition, temperature and system consumption.
Cooling, heating and electric water heating can change daily totals substantially.
What Does Solar Add?
Solar powers daytime loads and recharges the battery with what’s left.
Illustration: 3.5 peak sun hours × array rating × 80% system yield, rounded. Not a location-specific forecast. Household use draws from this energy too, so not all of it refills the battery. Shading, winter and cloudy days can sharply reduce production.
When Solar Isn’t Enough
Why This System?
The Quad Fortress Envy Duo 21 Hybrid Solar Kit is built around the Fortress Envy Duo 21, a hybrid inverter built around Fortress eBoost batteries and eWay mounts. Match the configuration to your daily energy use, the loads that run together and your installation.
120/240V split-phase output runs common household circuits and compatible 240V equipment. Manage what runs together and check motor starts for HVAC, pumps or shop tools.
Built-in busbars make battery connections fast and tidy.
Flexible string layout within the inverter’s limits.
Add a generator for long outages, or parallel units for larger systems.
The battery bank can deliver the inverter’s full output, the array is sized to recharge the battery, and strings are laid out within the inverter’s limits.
Choose Your Size
A balanced step up in solar and runtime.
Only the combinations shown in the product selector are offered. Every option uses the same Fortress Envy Duo 21 configuration.
Choose the Right Panel Electronics
Ground-mounted arrays and other installs where module-level rapid shutdown isn’t required. Includes PV disconnects.
Most roof-mounted arrays on buildings, where code requires module-level shutdown (NEC 690.12).
Rapid shutdown plus panel-level optimization and monitoring. Helps with mismatch from partial shade or different roof planes; it can’t recover sunlight lost to shade.
Other Sizes on This Platform
Reference: Fortress Envy Duo 21 manufacturer information.
Frequently Asked Questions
Contact SanTan Solar for help matching the system to your project.
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