Steca Solar Inverters

Few inverter brands can trace their roots to the 1970s. Steca was founded in 1976 in Memmingen, Bavaria, and it opened a solar electronics business in 1990, long before rooftop PV was mainstream.

Ownership has changed several times since. The company joined the PRIMEPULSE group in 2018 and was renamed KATEK Memmingen GmbH in 2019, keeping Steca as a product brand. After the Austrian technology group Kontron took over KATEK in 2024, the Memmingen business became Kontron Solar GmbH that June, and in 2025 it merged into Kontron eSystems GmbH. Development and production remain in Memmingen, with a second plant in Bulgaria.

Steca inverter range

Almost all Steca inverters are sold as StecaGrid. The coolcept family covers single-phase homes from 1.5 to 5 kW, and coolcept³ and the later fleX models extend it to three-phase roofs up to 10 kW. Older StecaGrid 8000 to 10000 3ph units and the 20000 to 46000 commercial inverters complete the grid-tied side, and SolBrid is a 10 kW three-phase hybrid for battery storage.

Two details in the model names help. A final 3 in the four-digit number marks a three-phase unit (StecaGrid 5013), and an x suffix is the outdoor version: the StecaGrid 3010 is rated IP21 for indoor mounting, the 3010x IP65.

What Steca is known for

German design and quiet operation. The coolcept housings are light — around 10 to 12 kg for a 3–6 kW unit — and the datasheets list noise of 25 to 31 dB, low enough for a hallway or utility room. Peak efficiency on the three-phase models reaches 98.7%.

The catch is that much of the range was designed in the 2010s for the panels of that time: one tracker per unit, modest input current and a high start-up voltage.

Matching panels to a Steca inverter

With Steca, the short string is as much a risk as the long one. The three-phase StecaGrid 3203 tracks only from 250 to 800 V, so on a hot afternoon, when each panel’s voltage sags, you need about nine modern 60-cell panels just to stay inside the window. The single-phase StecaGrid 3600 starts even higher, at 350 V. The ceiling is 1,000 V on the three-phase models and 845 V on the 3600, which leaves room for longer strings on a cold morning.

Current is the tighter limit. The coolcept³ units take 11 A per tracker and the StecaGrid 3600 12 A, less than the 13–14 A that 182 mm-cell modules deliver at full sun, so a modern large panel loses its peak. Run the pairing through the string calculator, which checks cold-weather voltage, the MPPT window and per-tracker current for each StecaGrid model.