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
The EG4 FlexBOSS18 is the better hybrid solar inverter overall, rated 4.4 to 3.5. The EG4 FlexBOSS18 leads on warranty, solar input and features. The SunGoldPower SPH10048P wins on value. The SunGoldPower SPH10048P costs $1,619.99 less ($1,580 vs $3,199.99).
SunGoldPower SPH10048P
A UL-listed 10 kW off-grid split-phase inverter at a low price per kW, for cabins, homes and shops that do not sell to the grid.
Amazon SunGoldPower $1,580$1,580
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 EG4 FlexBOSS18 for warranty (10-year warranty vs 1-year warranty), solar input (18,000 W of panels, 600 V max, 2 MPPTs vs 11,000 W of panels, 500 V max, 2 MPPTs) and features (UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, battery communication vs UL 1741 listed, Wi-Fi add-on, parallel stacking, battery communication; no grid sell-back).
- Choose the SunGoldPower SPH10048P for value ($158 per kW of continuous output vs $320 per kW of continuous output).
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 | EG4 FlexBOSS18 | SunGoldPower SPH10048P |
|---|---|---|
| Overall rating | 4.4/5 | 3.5/5 |
| Value 30% | 76 $320 per kW of continuous output | 100 $158 per kW of continuous output |
| Solar input 20% | 82 18,000 W of panels, 600 V max, 2 MPPTs | 48 11,000 W of panels, 500 V max, 2 MPPTs |
| Efficiency 20% | 68 94% peak efficiency, 60 W idle | 38 92% peak efficiency |
| Features 15% | 95 UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, battery communication | 65 UL 1741 listed, Wi-Fi add-on, parallel stacking, battery communication; no grid sell-back |
| Warranty 15% | 100 10-year warranty | 0 1-year warranty |
Specifications
| EG4 FlexBOSS18 | SunGoldPower SPH10048P | |
|---|---|---|
| Output | ||
| Output voltage | 120/240 V split-phase | 120/240 V split-phase |
| Continuous output | 10,000 W | 10,000 W |
| Surge | 20,000 W | 20,000 W |
| Peak efficiency | 94% | 92% |
| CEC efficiency | 97% | - |
| Idle draw | 60 W | - |
| Transfer time | 20 ms | 10 ms |
| Parallel units | Up to 16 units | Up to 6 units |
| Solar | ||
| Max PV power | 18,000 W | 11,000 W |
| Max PV voltage (Voc) | 600 V | 500 V |
| MPPT range | 120 to 440 V | 125 to 425 V |
| MPPT trackers | 2 | 2 |
| PV current per tracker | 26 A | 22 A |
| Runs without battery | - | Yes |
| Battery and grid | ||
| Battery voltage | 48 V | 48 V |
| Battery types | Lithium, lead-acid | Lithium, lead-acid, user-defined |
| Max charge current | 208 A | 200 A |
| AC charge current | - | 120 A |
| Battery communication | Yes | Yes |
| Grid sell-back | Yes | No |
| Generator input | - | No |
| UL 1741 | UL 1741 SB | Yes |
| Build | ||
| App monitoring | Included | Optional add-on |
| Enclosure | NEMA 4X | IP20 |
| Dimensions | 30.43 x 22.28 x 11.22 in | 620 x 445 x 130 mm |
| Weight | 115 lb | 59.5 lb |
| Warranty | 10 years | 1 year |
| Released | 2025-03 | 2023-08 |