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 rates 4.0 among 120/240 V split-phase hybrid solar inverters; the MPP Solar LV6548V 500V rates 3.3 among 120 V ones. The MPP Solar LV6548V 500V costs $420 less ($1,129 vs $1,549).
MPP Solar LV6548V 500V
#5 in 120 VFull review
A low-cost 6.5 kW off-grid inverter for big solar arrays on 120 V circuits. Pair two for a 240 V home.
MPP Solar US store $1,129$1,129
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.
Scores side by side
These two sit in different output classes (120/240 V split-phase and 120 V), and each is scored against the reference points for its own class, so a rating says how well each does among its own output peers. How we rank explains each factor.
| Factor weight | Fortress Power Solo 6.5K | MPP Solar LV6548V 500V |
|---|---|---|
| Overall rating | 4.0/5 | 3.3/5 |
| Value 30% | 92 $238 per kW of continuous output | 75 $174 per kW of continuous output |
| Solar input 20% | 69 10,000 W of panels, 550 V max, 2 MPPTs | 54 8,000 W of panels, 500 V max, 2 MPPTs |
| Efficiency 20% | 52 93% peak efficiency, 80 W idle | 32 91% 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 app, parallel stacking, battery communication; no grid sell-back |
| Warranty 15% | 44 5-year warranty | 0 1-year warranty |
Specifications
| Fortress Power Solo 6.5K | MPP Solar LV6548V 500V | |
|---|---|---|
| Output | ||
| Output voltage | 120/240 V split-phase | 120 V single-phase |
| Continuous output | 6,500 W | 6,500 W |
| Surge | 13,000 W | 13,000 W |
| Peak efficiency | 93% | 91% |
| 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 | 8,000 W |
| Max PV voltage (Voc) | 550 V | 500 V |
| MPPT range | 150 to 450 V | 90 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 |
| Max charge current | 140 A | 120 A |
| AC charge current | 80 A | 120 A |
| Battery communication | Yes | Yes |
| Grid sell-back | No | No |
| Generator input | Yes | No |
| UL 1741 | Yes | Yes |
| Build | ||
| App monitoring | Included | Included |
| Enclosure | IP20 | - |
| Dimensions | 27 x 16.1 x 6.1 in | 147.4 x 432.5 x 553.6 mm |
| Weight | 50.7 lb | 40.6 lb |
| Warranty | 5 years | 1 year |
| Released | 2026-01 | 2020-10 |