Solar Inverter Manufacturing: From Kassel to ABB Robots

A solar inverter turns the direct current from solar panels into the alternating current the grid uses, and every rooftop system and solar farm needs at least one. Solar inverter manufacturing has grown from SMA's first small string inverters in the 1990s to factories rated in tens of gigawatts a year. This post follows the trade from those early Sunny Boys through ABB's years as an inverter maker, which ended with the sale to FIMER in 2020 and restarted in 2025, to the factories opening this autumn in Germany, Texas and India, and looks at where ABB robots could fit on the lines.

An SMA Sunny Mini Central string inverter, photographed in 2011. Photo: Paul Broeker / Wikimedia Commons (CC BY-SA 4.0)

From a Kassel spin-out to ABB's inverter years

SMA started in 1981 as SMA Regelsysteme GmbH, a spin-out of the University of Kassel, and its first products were industrial computers. A federal solar roof programme in 1990 pushed it toward compact, fully automatic inverters, and by 1995 it had the Sunny Boy SWR 700, a string inverter for a row of series-wired modules of up to 1 kWp. A transformerless model, the SWR 1500, followed in 1996. Efficiency climbed from about 90 percent in 1990 to as much as 98 percent in transformerless models while the price per kilowatt fell by about half, and many other makers took up SMA's string concept.

An SMA Sunny Boy SWR 3000 string inverter on a wall in Dornbirn, Austria, in 2021. Photo: Asurnipal / Wikimedia Commons (CC BY-SA 4.0)

Others tried putting a small inverter behind every panel. Werner Kleinkauf, one of SMA's founders, worked on module integrated converters at the ISET institute in the late 1980s, and Mastervolt's Sunmaster 130S of 1993, developed with Shell Solar, Ecofys and ECN, was the first true microinverter. Most of those early projects had ended by 2003. Enphase Energy, founded in 2006 by Martin Fornage and Raghu Belur, released the M175 in 2008, the first commercially successful microinverter. Even so, string inverters held about 61.6 percent of the market in 2019, central inverters 36.7 percent and microinverters 1.7 percent, according to Fraunhofer data.

An Enphase M190 microinverter mounted on a roof rail during an installation in 2011. Photo: Maury Markowitz / Wikimedia Commons (CC BY-SA 3.0)

ABB opened its first production line for solar string inverters in Jüri, Estonia, in October 2011, with a yearly capacity of 400 MW, and every inverter was tested and its efficiency measured before it left the plant. In 2013 ABB bought Power-One and its solar inverter business. By 2018 the unit had about 800 employees in more than 30 countries, plants and R&D in Italy, India and Finland, and revenue of about $290 million. In July 2019 ABB agreed to pass it to FIMER, an Italian welding equipment maker that had built welding inverters since 1983 and entered solar in 2007. Reuters reported that ABB would pay up to $470 million, and the sale closed in March 2020.

The floating solar test bed on Singapore's Tengeh Reservoir, where ABB supplied 100 kW of TRIO-50 string inverters in 2017. Photo: ABB

New gigawatt factories and the robots inside them

On 17 September SMA opened its Gigawatt Factory in Niestetal near Kassel, an investment of about €80 million with room for more than 60 GW of output a year. It builds Sunny Central central inverters from 2.6 to 5 MW, Sunny Highpower Peak3 string inverters of up to 180 kW and the containerised Sunny Central Flex. New KUKA robots and other automated systems handle assembly, screwdriving and critical steps with silicon carbide semiconductors, while automated guided vehicles and lifts move 40-foot containers weighing up to 40 tonnes. Two shifts of 50 to 60 people work the production lines, and SMA expects about 200 employees in production at full capacity next year.

The sign on SMA's new Gigawatt Factory in Niestetal near Kassel, which opened in September 2026. Photo: SMA

Rules are also changing where inverters can come from. On 28 July the US Federal Communications Commission added foreign-produced power inverters to its covered list, which stops new equipment authorizations for unapproved foreign models, and Intertek CEA expects US manufacturing to meet only about 40 percent of solar and storage demand through 2027. Power Electronics of Spain has started building a 40 GW campus in Houston with automated production and new inverter lines. In India, Waaree Power started a 1.1 GW line in Gujarat in October, taking it to 4.15 GW of string inverter capacity, and FIMER showed its 2 MW PVS990 central inverter at REI Expo in late October.

Inverter housings at the Suzu photovoltaic power station, 2014. Photo: Qurren / Wikimedia Commons (CC BY-SA 3.0)

ABB has also come back to the business it left. In December 2025 it completed the purchase of Gamesa Electric's power electronics business in Spain from Siemens Gamesa, which brought utility-scale solar inverters, about 400 employees and two converter factories, in Madrid and Valencia. In June 2026 it launched the Proteus range of solar inverters and battery storage converters, quoting efficiency of up to 99.45 percent. We found no public example of ABB robots on an inverter line, at those plants or anywhere else, so robots there are a possibility. SMA gave its robots assembly and screwdriving, the tasks ABB names for its IRB 930 SCARA, launched in 2023 with up to 250 N of push-down force for screwdriving.

An inverter station from ABB's Proteus range between rows of panels at a utility-scale solar plant. Photo: ABB

Where inverter factories go next

SMA designed its new lines to switch products. They build DC-AC power blocks now, and the company plans to make DC-DC power systems for hybrid solar and storage plants and for power-to-gas on the same lines instead of giving each product its own line. ABB's own Smart Power plant in Vaasa, Finland, already works this way with switchgear: a JOT Automation line with 20 ABB robots, ten of them IRB 1200s, has made eight models since early 2024 by changing programs instead of tools, and its cells were first tested as virtual models in RobotStudio. Our post on PCB assembly robot cells covers the circuit boards inside each inverter.

An ABB robot assembling switchgear parts in a JOT Automation cell at ABB Smart Power in Vaasa, Finland. Photo: ABB

The FCC rule also reaches homes. It applies to utility-interactive inverters with wired or wireless connections, so new foreign models for rooftops are caught along with those for solar farms. Waaree puts the global inverter market at about $16 billion in 2025, growing by about 11 percent a year over the next decade, and sees India as an alternative supply base for buyers in the United States and Europe. The closest real ABB robot project in solar is at Absolicon in Härnösand, Sweden, where two ABB robots build a solar collector every six minutes, against up to three a day by hand. Our post on solar module manufacturing covers robots on the panel side.

An ABB robot above a collector trough on Absolicon's solar collector line in Härnösand, Sweden. Photo: ABB

Cost is the first open problem. SMA spent about €80 million on its plant, and PV Tech's chart of the week on 1 October forecast that European inverter output would rise in 2027 while factory utilisation drops, and lower utilisation makes a new line harder to pay back. Skills are the second. SMA runs its new lines with 50 to 60 people per shift and plans about 200 in production at full capacity, so a small team has to program, maintain and troubleshoot a lot of automation. SMA also calls its silicon carbide steps critical, and testing every finished unit, as ABB's Estonian line did in 2011, adds stations that someone has to run.

An engineer with an ABB IRB 930 SCARA robot, launched in 2023 for electronics and battery assembly. Photo: ABB

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