KACO new energy: PV string, hybrid and battery inverters from a Siemens subsidiary

Overview

KACO's roots go back to 1914, when Gustav Bach, Albert Hirth and Gustav Klein founded the company in Heilbronn. According to its history, KACO built its first thyristor inverter in 1953. In 1998/99 the inverter business was spun off as KACO Gerätetechnik GmbH and launched the PVI 2600, which the company describes as the world's first transformerless PV string inverter. The business took the name KACO new energy in 2009 and had sold more than 10 GW of inverter power by 2017.

Since the end of April 2019 KACO new energy has been wholly owned by Siemens AG and sits in its Smart Infrastructure business, where it specialises in power electronics for decentralised energy supply. The company page calls it a medium-sized company that sells worldwide.

What sets KACO apart today is its focus on string inverters for large plants. Rather than one central inverter per block, it argues for many string units spread through the field, which its product pages call a "virtual central" design. The same silicon carbide platform carries its battery inverters, so a solar plant and a storage system can use related hardware from one supplier.

Offering

KACO's product range falls into string and hybrid inverters, battery inverters, PV monitoring, accessories and services.

String and hybrid inverters

The blueplanet 87.0 to 125 TL3 family serves commercial rooftops and ground-mounted plants. It accepts 1,000 V and 1,500 V modules, connects to 380, 400 or 480 V lines, allows a 1.5:1 DC:AC ratio on the 92.0 TL3 and lets the 105 TL3 draw 15% more power from the same hardware's thermal reserve. Integrated DC disconnects and type 1+2 surge arresters are standard. For homes and small businesses, the blueplanet hybrid NH3 series covers 6 to 12 kW with backup operation and a built-in home energy management system.

Battery inverters

The blueplanet gridsave series is a family of bidirectional battery inverters on one platform: the established 92 to 137 kVA first generation, a second generation up to 150 kVA with DC up to 1,450 V and improved cybersecurity, a 100 to 165 kVA grid-forming version for island and backup operation, and an HV version for 1,500 V batteries. KACO quotes up to 98.9% efficiency, under 60 dB noise and about 80 kg per unit.

Monitoring and services

The blue'Log X-series data loggers record data and control PV plants, blueplanet smartcloud provides monitoring, and the Leaflet HEMS blueplanet edition manages household energy, as listed under PV monitoring.

Technology

KACO builds its recent inverters on silicon carbide power semiconductors, which it credits for the high DC:AC ratio and late thermal derating of the blueplanet TL3 family and the 98.9% peak efficiency of the gridsave battery inverters.

For monitoring, the blueplanet 87.0 to 165 TL3 operating manual (Q2 2026, firmware 03.59 onwards) documents two Ethernet connections with TCP/IP and a Modbus TCP server based on SunSpec, on default port 502, with write access that can be switched off. Because the register layout follows SunSpec information models such as the three-phase inverter model 103, a SunSpec-aware client can discover the inverter's values instead of relying on a vendor-specific table. The same manual describes two RS-485 ports using KACO's own protocol, one of them reserved for a string combiner, so the serial port is not a Modbus route.

The gridsave series exposes Modbus TCP and MQTT for energy and battery management systems, supports reactive power and fast frequency response, and is IP66 / NEMA 4X rated for outdoor installation. KACO states that its cybersecurity follows Siemens standards. Remote commissioning and firmware updates are offered on the commercial string inverters.

Customers

KACO publishes few named customers; most of its sales go through distributors, installers and project developers. The clearest current reference is on the gridsave series page: a 1 MWh, roughly 400 kW storage facility at Kibbutz Maale-Gilboa in Israel built on four blueplanet gridsave 92.0 TL3-S battery inverters. KACO also states that the first-generation gridsave platform has thousands of installations behind it.

Grid operators approve KACO equipment for connection. In February 2025 ELES, the Slovenian transmission system operator, added several of KACO's newer inverters to its list of approved equipment, as reported on the company page.

KACO lists a Top Brand PV award for 2021 to 2024, and its blueplanet 125 TL3 went on sale worldwide in September 2018. Residential customers reach KACO through installers selling the hybrid NH3 series, which pv magazine reported in October 2024 is compatible with batteries from several manufacturers and offers a Consolinno home energy management option.

Markets

KACO sells worldwide. At the time of the Siemens deal in 2019, it was active in more than nine countries through local sales and service companies, according to Solar Power World. Its applications menu covers residential, commercial and industrial, and utility-scale PV, plus battery storage for commercial sites and the grid.

The commercial and utility string inverters target rooftops, carports and ground-mounted plants, including hot climates where late power derating matters. The gridsave battery inverters target self-consumption, peak shaving, load management, energy arbitrage, EV charging support, grid services, backup and microgrids, and large utility batteries.

KACO's market narrowed before the Siemens acquisition. In January 2019 it sold its central inverter operations, based in South Korea, to OCI Power, and Siemens bought only the string inverter business, leaving KACO's project development and EPC activities outside the deal, as PV Tech reported. KACO now supplies equipment rather than building plants.

Company

KACO new energy GmbH is registered at the Stuttgart local court under HRB 106817, with its head office at Werner-von-Siemens-Allee 1, Neckarsulm, according to its legal notice. The managing directors are Jens-Ole Kück, Matthias Haag and Martin Rohrmeier, and the company presents itself as "A Siemens Company".

Siemens announced in March 2019 that it would buy KACO's string inverter business for an undisclosed sum. Jean-Christoph Heyne, then head of Siemens' Future Grids business, said the deal strengthened Siemens' grid-edge portfolio, which also included home batteries, containerised storage and the Fluence joint venture with AES (PV Tech). KACO's history records that Siemens AG acquired 100% of the shares of KACO new energy GmbH with effect from 30 April 2019.

At the time of the acquisition KACO had more than 350 employees (Solar Power World). Current headcount and revenue are not published separately from Siemens.