The Sungrow SG15/17/20RT-P2 series are three-phase grid-tie inverters designed for commercial installations and larger domestic systems, where stable operation and high energy yield throughout the year are crucial. What sets them apart is their wide MPPT operating range and low startup threshold, allowing them to capture morning production faster and maintain performance under weaker sunlight conditions. The use of 2 independent MPPTs facilitates the design of rooftop systems with different orientations or partial shading - each tracker can optimise a different string, minimising energy losses.
In practice, high European efficiency is also important, as it better reflects the real operating conditions in Poland compared to laboratory maximums, translating to greater annual production. The series offers 24/7 monitoring, remote updates, and convenient operation via an app, with communication available through both WiFi and Ethernet. Plus: built-in protections (including Type II SPD and fast arc detection) and a robust outdoor enclosure. These are not hybrid inverters - they are not designed for direct integration with energy storage systems.
Ranking
Specifications
Pros and cons
The MPPT voltage range of 160-1000 V DC ranks among the widest available in three-phase 15-20 kW inverters. The 160 V lower threshold enables power generation under extremely low-irradiance conditions (dawn, dusk, heavy overcast), which in temperate climates translates into measurably higher annual energy yield compared to units with a start-up threshold of ≥200 V.
Arc-fault circuit interruption (AFCI 2.0, compliant with IEC 62109-2) and a DC surge protective device (SPD) Type II are included as standard from the factory - on competing platforms such as the Fronius Symo, DC SPD is an optional paid accessory. This reduces total system BoS cost and enhances fire safety with no additional investment.
Sungrow ranked 1st in the BloombergNEF Inverter Bankability Survey 2025 with 100% recognition among respondents - for the sixth consecutive year. Strong bankability translates directly into warranty coverage, after-sales service availability, and spare parts supply throughout the full 10-year product warranty period.
The RT-P2 series achieves a European efficiency of up to ~98.4%, placing it at the top of the 15-20 kW class and exceeding the stated European efficiency of the Fronius Symo (~97.0%). The ~1.4 percentage-point difference over a full year for a 20 kW system corresponds to approximately 200-250 kWh of additional energy production annually.
The RT-P2 series is a grid-tie-only inverter with no built-in battery interface. Adding energy storage to the system requires replacing the unit with a hybrid inverter (e.g., Sungrow SH-RT) or integrating an AC-coupled external storage solution, either of which significantly increases the cost of any future system upgrade.
Two independent MPPTs are sufficient for typical dual-pitch roof configurations, but on roofs with 3-4 distinct orientations or with distributed shading, the unit is outperformed by inverters offering 4 MPPTs (e.g., Huawei SUN2000-20KTL-M2). This limitation may necessitate the use of power optimizers or an additional string inverter, increasing overall project cost.
Alternatives
About the SG15/17/20RT-P2 series
These answers cover the whole series. Where a figure differs, the specification above is this model's own.