KOSTAL Solar Inverters

KOSTAL is a German family business with more than a century of engineering behind it. The KOSTAL Group has existed since 1912 and today consists of seven independent companies, from automotive electrics and electric-vehicle chargers to connectors and industrial electronics. KOSTAL Solar Electric GmbH was set up in 2006 in Freiburg im Breisgau as the group’s inverter company.

The solar company develops and produces its inverters in Germany, has eight locations in Europe and sells mainly through qualified installers, whom it lists in an installer search on its website. It marked its twentieth anniversary in 2026.

KOSTAL inverter range

The first PIKO — short for “Photovoltaik Inverter KOSTAL” — was the three-phase PIKO 5.5 of 2007. In 2013 the PIKO BA combined solar generation and a high-voltage battery in one three-phase unit, and the PLENTICORE plus followed in 2018 as a hybrid that could take a battery at installation or years later.

Today’s range is built around the PLENTICORE. The PLENTICORE plus G2 covers 3 to 10 kW, and the third generation launched in 2024, PLENTICORE G3, spans 4 to 20 kW in three frame sizes marked S, M and L in the model name, from the S4.0 to the L20. All of them are hybrids that work with or without a battery; the older PIKO 4.2 is a plain string inverter.

What KOSTAL is known for

German development and manufacturing, a three-phase heritage going back to the first PIKO, and hybrids that can run as plain grid-tied inverters until the owner decides to add storage. KOSTAL calls the G3 its first true universal inverter for that flexibility.

The installer-led sales model means you normally buy and commission a KOSTAL through a partner rather than online, and the older PIKO and G2 models were designed around smaller panels than the G3.

Matching panels to a KOSTAL inverter

The PLENTICORE plus G2 allows 1,000 V, but its tracking window ends at 720 V. That gap matters: a string of twenty 34 V-at-maximum-power panels sits at 680 V on a mild day and climbs past 720 V on a cold, bright one, where the inverter can no longer follow the best operating point. Eighteen panels is a more comfortable length. Each tracker takes 15 A, fine for 182 mm-cell modules but below the 17–18 A of 210 mm-cell panels.

The G3 widens the window to 75–800 V and raises the current to 17 A on the S models and 30 A on the M and L models — enough for two parallel strings of standard panels. The string calculator checks each PLENTICORE model for cold-weather voltage, the MPPT window and per-tracker current.