Fortress Power Solo 6.5K
For off-grid cabins, ADUs and backup systems that want 240 V and a large solar input from a US-supported brand. It costs a little more than the EG4 6000XP.
Current Connected $1,549 Wind & Sun $1,549$1,549
The Fortress Power Solo 6.5K and the Fortress Power Envy 8K are evenly matched, rated 4.0 and 4.0. The Fortress Power Solo 6.5K leads on value. The Fortress Power Envy 8K wins on warranty, features and efficiency. The Fortress Power Solo 6.5K costs $2,186 less ($1,549 vs $3,735).
Fortress Power Envy 8K
For grid-tied homes with moderate backup needs that want an outdoor hybrid with export and US-based support.
Wind & Sun $3,735$3,735
Prices were last checked October 23, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Fortress Power Solo 6.5K for value ($238 per kW of continuous output vs $467 per kW of continuous output).
- Choose the Fortress Power Envy 8K for warranty (10-year warranty vs 5-year warranty), features (UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, generator input, battery communication vs UL 1741 listed, Wi-Fi app, parallel stacking, generator input, battery communication; no grid sell-back) and efficiency (94% peak efficiency, 70 W idle vs 93% peak efficiency, 80 W idle).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 120/240 V split-phase hybrid solar inverter; a clear win is highlighted. How we rank explains each one.
| Factor weight | Fortress Power Solo 6.5K | Fortress Power Envy 8K |
|---|---|---|
| Overall rating | 4.0/5 | 4.0/5 |
| Value 30% | 92 $238 per kW of continuous output | 47 $467 per kW of continuous output |
| Solar input 20% | 69 10,000 W of panels, 550 V max, 2 MPPTs | 74 13,000 W of panels, 600 V max, 2 MPPTs |
| Efficiency 20% | 52 93% peak efficiency, 80 W idle | 63 94% peak efficiency, 70 W idle |
| Features 15% | 85 UL 1741 listed, Wi-Fi app, parallel stacking, generator input, battery communication; no grid sell-back | 100 UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, generator input, battery communication |
| Warranty 15% | 44 5-year warranty | 100 10-year warranty |
Specifications
| Fortress Power Solo 6.5K | Fortress Power Envy 8K | |
|---|---|---|
| Output | ||
| Output voltage | 120/240 V split-phase | 120/240 V split-phase |
| Continuous output | 6,500 W | 8,000 W |
| Surge | 13,000 W | 16,000 W |
| Peak efficiency | 93% | 94% |
| CEC efficiency | - | 96.5% |
| Idle draw | 80 W | 70 W |
| Transfer time | 10 ms | 20 ms |
| Parallel units | Up to 6 units | Up to 10 units |
| Solar | ||
| Max PV power | 10,000 W | 13,000 W |
| Max PV voltage (Voc) | 550 V | 600 V |
| MPPT range | 150 to 450 V | 170 to 500 V |
| MPPT trackers | 2 | 2 |
| PV current per tracker | 18 A | 25 A |
| Runs without battery | Yes | Yes |
| Battery and grid | ||
| Battery voltage | 48 V | 48 V |
| Battery types | Lithium, lead-acid | Lithium, lead-acid |
| Max charge current | 140 A | 167 A |
| AC charge current | 80 A | - |
| Battery communication | Yes | Yes |
| Grid sell-back | No | Yes |
| Generator input | Yes | Yes |
| UL 1741 | Yes | UL 1741 SB |
| Build | ||
| App monitoring | Included | Included |
| Enclosure | IP20 | IP65 (NEMA 4X) |
| Dimensions | 27 x 16.1 x 6.1 in | 29.5 x 20.5 x 11.23 in |
| Weight | 50.7 lb | 110 lb |
| Warranty | 5 years | 10 years |
| Released | 2026-01 | 2023-06 |