EG4 FlexBOSS21
For grid-tied homes that want whole-house backup and a big solar array from one inverter. It gives more output than the 18kPV for less money.
Signature Solar $3,599.99$3,599.99
4.5/5
For grid-tied homes that want solar, battery backup and export in one outdoor box at a lower price than Sol-Ark or Fortress.
- 10 kWOutput
- 48 VBattery
- 15,000 WSolar input
- 60 WIdle draw
- 10 yearsWarranty
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Price checked October 23, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- Sells power back to the grid with UL 1741 SB, so it qualifies for net metering
- Outdoor-rated IP65 case mounts outside next to the panel
- Takes 15,000 W of panels on three trackers
- Ten-year warranty and built-in monitoring
Cons
- Weighs about 94 lb, a two-person mount
- Install manual targets licensed installers; DIY setup is involved
How it scores
The rating comes from 5 measured or published factors, each scored 0-100 against fixed reference points for its output. How we rank explains each one.
Specifications
| Model number | SPH 10000TL-HU-US (B) |
|---|---|
| Output | |
| Output voltage | 120/240 V split-phase |
| Continuous output | 10,000 W |
| Surge | 15,000 W |
| Max efficiency | 98.1% |
| CEC efficiency | 97% |
| Idle draw | 60 W |
| Transfer time | 10 ms |
| Parallel units | Up to 6 units |
| Solar | |
| Max PV power | 15,000 W |
| Max PV voltage (Voc) | 525 V |
| MPPT range | 150 to 450 V |
| MPPT trackers | 3 |
| PV current per tracker | 22 A |
| Runs without battery | Yes |
| Battery and grid | |
| Battery voltage | 48 V |
| Battery types | Lithium, lead-acid |
| Max charge current | 200 A |
| Battery communication | Yes |
| Grid sell-back | Yes |
| Generator input | Yes |
| UL 1741 | UL 1741 SB |
| Build | |
| App monitoring | Included |
| Enclosure | IP65 (NEMA 4) |
| Dimensions | 457 x 874 x 256 mm |
| Weight | 93.7 lb |
| Warranty | 10 years |
| Released | 2024-05 |
Alternatives in this output
EG4 FlexBOSS18
For grid-tied homes that want net metering and whole-home backup at a lower price than the FlexBOSS21. Choose the 21 if you need more battery-only output or a third tracker.
Signature Solar $3,199.99$3,199.99
Fortress Power Envy Duo 21
For homes with a large roof array that want whole-house backup and grid export from one outdoor unit. It takes more solar than the Envy True 12 for the same price.
Wind & Sun $4,898$4,898
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