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 is the better hybrid solar inverter overall, rated 4.0 to 3.7. The Fortress Power Solo 6.5K leads on warranty and features. The SunGoldPower SPH6548P costs $399 less ($1,150 vs $1,549).
SunGoldPower SPH6548P
A low-cost UL-listed split-phase inverter for off-grid homes and backup with a generator.
Amazon SunGoldPower $1,150$1,150
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 warranty (5-year warranty vs 1-year warranty) and features (UL 1741 listed, Wi-Fi app, parallel stacking, generator input, battery communication; no grid sell-back vs UL 1741 listed, Wi-Fi add-on, parallel stacking, generator input, battery communication; no grid sell-back).
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 | SunGoldPower SPH6548P |
|---|---|---|
| Overall rating | 4.0/5 | 3.7/5 |
| Value 30% | 92 $238 per kW of continuous output | 100 $177 per kW of continuous output |
| Solar input 20% | 69 10,000 W of panels, 550 V max, 2 MPPTs | 69 10,000 W of panels, 550 V max, 2 MPPTs |
| Efficiency 20% | 52 93% peak efficiency, 80 W idle | 45 93% peak efficiency |
| Features 15% | 85 UL 1741 listed, Wi-Fi app, parallel stacking, generator input, battery communication; no grid sell-back | 75 UL 1741 listed, Wi-Fi add-on, parallel stacking, generator input, battery communication; no grid sell-back |
| Warranty 15% | 44 5-year warranty | 0 1-year warranty |
Specifications
| Fortress Power Solo 6.5K | SunGoldPower SPH6548P | |
|---|---|---|
| Output | ||
| Output voltage | 120/240 V split-phase | 120/240 V split-phase |
| Continuous output | 6,500 W | 6,500 W |
| Surge | 13,000 W | 13,000 W |
| Peak efficiency | 93% | 93% |
| Idle draw | 80 W | - |
| Transfer time | 10 ms | 10 ms |
| Parallel units | Up to 6 units | Up to 6 units |
| Solar | ||
| Max PV power | 10,000 W | 10,000 W |
| Max PV voltage (Voc) | 550 V | 550 V |
| MPPT range | 150 to 450 V | 150 to 450 V |
| MPPT trackers | 2 | 2 |
| PV current per tracker | 18 A | 18 A |
| Runs without battery | Yes | Yes |
| Battery and grid | ||
| Battery voltage | 48 V | 48 V |
| Battery types | Lithium, lead-acid | Lithium, lead-acid, user-defined |
| Max charge current | 140 A | 140 A |
| AC charge current | 80 A | 80 A |
| Battery communication | Yes | Yes |
| Grid sell-back | No | No |
| Generator input | Yes | Yes |
| UL 1741 | Yes | Yes |
| Build | ||
| App monitoring | Included | Optional add-on |
| Enclosure | IP20 | IP20 |
| Dimensions | 27 x 16.1 x 6.1 in | 23 x 16.2 x 5.2 in |
| Weight | 50.7 lb | 42 lb |
| Warranty | 5 years | 1 year |
| Released | 2026-01 | 2024-08 |