The hybrid inverter is the brain of a solar-plus-storage system — it determines what your system can and can't do. Three inverters dominate the residential and light commercial market right now: the Sol-Ark 15K-2P, the EG4 18kPV, and the Sigenergy SigenStor. We carry and sell all three at Solwel, and here's how they actually compare.
Quick Comparison
| Sol-Ark 15K-2P | EG4 18kPV | Sigenergy SigenStor | |
|---|---|---|---|
| Continuous Output | 15 kW | 18 kW | 3.8–11.5 kW (scalable) |
| Phase | Split-phase 120/240V | Split-phase 120/240V | Split-phase 120/240V |
| Off-Grid Capable | Yes | Yes | Yes |
| Battery Compatibility | Open — most major LFP brands | EG4 native + many third-party | Sigenergy SigenStor only |
| EV Charging | No (EVSE via load output) | No (EVSE via load output) | Yes — built-in bidirectional DC V2H |
| Warranty | 10 years | 10 years | 10 years |
| Made in USA | Yes (San Antonio, TX) | No | No |
| Certifications | UL 1741, UL 1741 SA | UL 1741 | UL 1741 |
Sol-Ark 15K-2P — Best For: Open Battery Compatibility, Off-Grid, U.S.-Made
The Sol-Ark 15K is the most versatile inverter in this group. Sol-Ark is a San Antonio, Texas-based company — which means U.S.-based engineering, support, and warranty service. That matters for commercial projects, for customers who care about domestic manufacturing, and for installers who've dealt with overseas warranty headaches.
Sol-Ark's biggest technical differentiator is open battery compatibility. The 15K works with virtually every major LFP battery brand via CAN/RS485 — FranklinWH, EG4, Pylontech, BYD, and others. If your customer already has batteries, or if you want flexibility to spec the best battery for each project, Sol-Ark gives you the most options.
The 15K is also a true off-grid-capable inverter — it can fully island from the grid and run an entire home from solar and storage indefinitely. Combined with its UL 1741 SA certification, it's one of the few residential inverters that meets advanced grid support requirements in California, Hawaii, and other states with strict interconnection rules.
At 15 kW, it's sized for most homes — 2,000–4,500 sq ft, central HVAC, EV charger. For larger loads, Sol-Ark's 30K and 60K commercial units scale up.
Ideal install scenario: Projects requiring maximum battery flexibility, off-grid or hybrid-grid systems, California/Hawaii installs requiring UL 1741 SA, customers who value U.S.-based support.
EG4 18kPV — Best For: High-Output Residential, EG4 Ecosystem, Value
The EG4 18kPV punches above its price point. At 18 kW continuous output, it's the most powerful single-phase hybrid inverter in this comparison — making it a strong fit for larger homes, homes with EV chargers, or installations where the customer wants significant headroom for future load growth.
Like all EG4 inverters, it supports both grid-tied and off-grid operation. It's natively compatible with EG4's WallMount and other EG4 battery products via CAN bus, and also supports many third-party LFP batteries through standard protocols.
EG4 has rapidly built a strong installer community in the U.S., with active forums, good documentation, and competitive pricing. For installers looking to build repeatable, high-value residential systems without the Sol-Ark price premium, the 18kPV is a compelling option.
Ideal install scenario: Larger homes (3,500–5,000+ sq ft), high-load households with EV charging, installers building standardized EG4 system packages, budget-conscious projects needing maximum output per dollar.
Sigenergy SigenStor — Best For: EV Integration, All-in-One Simplicity
Sigenergy takes the most integrated approach of the three. The SigenStor isn't just a hybrid inverter — it's a 5-in-1 energy system combining a solar inverter, battery PCS, EMS, load management, and a bidirectional DC EV charger in a single unit. No separate EV charger required, and the V2H (vehicle-to-home) capability means a compatible EV can actually power your house during an outage.
The tradeoff for that integration is a closed ecosystem. The SigenStor only works with Sigenergy's own battery packs. You can't mix in EG4 or FranklinWH batteries. If a customer is open to an all-Sigenergy system, this is a non-issue — the system is clean, elegant, and genuinely impressive. If they have existing equipment or want future flexibility, it's a meaningful constraint.
The scalable output (3.8–11.5 kW depending on configuration) makes it suitable for a range of home sizes, though it tops out lower than the Sol-Ark and EG4 on raw output power.
Ideal install scenario: New construction or full system installs where the customer wants EV integration, V2H capability, and an all-in-one system from a single manufacturer.
Bottom Line
- Maximum flexibility and battery choice? Sol-Ark 15K.
- Most output per dollar and high-load homes? EG4 18kPV.
- EV integration and all-in-one simplicity? Sigenergy SigenStor.
All three are solid products that we install confidence in selling. The right choice almost always comes down to the specific project — load profile, battery preference, EV situation, and budget. Our team works through these decisions every day with installers across the country. Call us at (346) 432-4228 or submit a quote request and we'll help you spec the right system.