Dual Fortress Solo 6.5K Off-Grid Solar Kit | 13kW 120/240V | 7.2kW Solar | 21.6kWh Battery
Price range: $13,150.00 through $14,356.82
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A solar kit built around two Fortress Solo 6.5K off-grid inverters.
- 13 kW continuous 120/240V split-phase output
- Solar: 18 × 400W panels (7.2 kW DC)
- Storage: 21.6 kWh (4 × 5.4 kWh Wall/Floor-Mount) Fortress eFlex MAX 5.4 kWh LiFePO4
- Optional Tigo rapid shutdown or Tigo optimizers
- Grid-connected backup, no export
Racking sold separately.
Dual Fortress Solo 6.5K Off-Grid Solar Kit | 13kW 120/240V | 7.2kW Solar | 21.6kWh Battery
This kit is built around two Fortress Solo 6.5K off-grid inverters, delivering 13 kW of continuous 120/240V split-phase output, paired with 18 × 400W panels (7.2 kW DC) and 21.6 kWh (4 × 5.4 kWh Wall/Floor-Mount) of storage.
- 13 kW continuous AC output, 120/240V split-phase
- Surge capacity up to 26 kW for motor starting
- Solar array: 18 × 400W panels (7.2 kW DC)
- Battery options: 21.6 kWh (4 × 5.4 kWh Wall/Floor-Mount) (Fortress eFlex MAX 5.4 kWh LiFePO4)
- Grid-connected backup, no export
- Optional Tigo rapid shutdown or Tigo optimizers + rapid shutdown
Choose Your Configuration
| Battery Storage | 21.6 kWh (4 × 5.4 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 | ~12,200 (18P) kWh/year |
| Chicago, Illinois | ~9,100 (18P) 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. It connects to the grid for charging and backup but does not export power.
Ideal Applications
- Outage backup for the essentials plus one large appliance, such as central A/C or an electric water heater
- Starter off-grid homes with efficient loads
What’s Included
- Two Fortress Solo 6.5K off-grid inverter units
- ALEX-400 400W solar panels (count per configuration)
- Fortress eFlex MAX 5.4 kWh LiFePO4 (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 Solo 6.5K |
| Inverter Quantity | Dual |
| Continuous Output | 13 kW |
| Inverter Size (KW) | 10KW-15KW |
| Output (V) | 120V/240V |
| Grid Connection | Grid-Connected Backup (No Export) |
| Generator Compatible | Yes |
| Inverter Type | All-in-one Inverter |
| Solar Capacity (DC) | 5KW-10KW |
| Battery Capacity (KWH) | 20KWH–30KWH |
| Solar Array | 18 Panels (7.2 kW) |
| Battery Storage | 21.6 kWh |
| Rapid Shutdown | None, Tigo Optimizers + Rapid Shutdown, Tigo Rapid Shutdown |
What Can It Power?
Built around the Fortress Solo 6.5K, a compact off-grid inverter with Fortress eFlex batteries, this kit delivers 13 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 13 kW continuous and 26 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 (17.28 kWh from 21.6 kWh).
34.6 hrs
17.3 hrs
8.6 hrs
4.3 hrs
2.7 hrs
1.3 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 Dual Fortress Solo 6.5K Off-Grid Solar Kit is built around the Fortress Solo 6.5K, a compact off-grid inverter with Fortress eFlex batteries. 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.
Inverter, solar charging and battery charging in one unit.
Flexible string layout within the inverter’s limits.
Charge from a generator during long low-sun periods (generator sold separately).
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 Solo 6.5K 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 Solo 6.5K manufacturer information.
Frequently Asked Questions
Contact SanTan Solar for help matching the system to your project.
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