Innovative milestones in inverter history

KOSTAL Solar Electric was founded in 2006 and is one of the leading suppliers of innovative string inverters for the private and small business sector. From the very beginning, KOSTAL Solar Electric has successively developed its range of devices and has always focused on the highest quality, which has also been an integral part of how all divisions of the KOSTAL Group have perceived themselves since 1912.

KOSTAL Solar Electric has remained true to its philosophy since the very start and has therefore created innovative power electronics and photovoltaic technology that meet the highest quality standards. To this end, KOSTAL develops and produces modern inverters to generate alternating current from solar power and to make it available for the electricity required in the building as well as for the public grid.

2007: PIKO – the first three-phase feed-in inverter

Together with the Fraunhofer Institute and Solarfabrik, KOSTAL developed its first solar inverter called "Convert 6T". It was some time later that the device was given its actual name: PIKO. The abbreviation stands for “Photovoltaic Inverter KOSTAL”.

The compact PIKO 5.5 was a ground-breaking product of the first power electronics generation. Contrary to the mainstream at the time, the inverter had a three-phase design. In addition, at 5.5 kW the PIKO was powerful and already had three DC inputs. This made the KOSTAL inverter a pioneer in the flexible design of the solar strings that connect the modules to the inverter. Due to the maximum permissible phase unbalanced load of 4.6 kW, the PIKO 5.5 outperformed single-phase market competitors with 20% more rated output.

Equipped with central network interfaces and an integrated data logger, i.e. providing the option of viewing data using a web-based application and integrated display, customers were impressed by how easy the PIKO was to use. The optical push-button on the PIKO 5.5 was a fantastic detail, designed for many years of use in PV operation.

The success was so great that the next chapter in the KOSTAL inverter's success story was written in 2008 with a new series of the PIKO with 10 kW and later even with 20 kW. The PIKO series has continued to launch several successor models onto the market, but the name has remained and today is still synonymous with innovation and success.

2009: PIKO 3.0/3.6 – first single-phase inverter

Three-phase feed-in into the public supply grid to avoid imbalances is advantageous and suitable for the grids used in many European countries and connection points.

However, especially in Southern Europe, single-phase house connections are also common, so KOSTAL has introduced the single-phase models PIKO 3.0 and 3.6 for these purposes.

By connecting two AC bridge sections in parallel, it was possible to apply the circuit concept of the three-phase devices that had been tried and tested for this purpose.

2009: First integration of a DC voltage separator

In order to reduce system costs and make inverter installation even easier, KOSTAL has equipped its inverters with a DC voltage separator. Here KOSTAL has managed to integrate an electronic solution using an innovative safety concept.

2012: Arc detection – first innovative prevention function in the inverter

Fascinated by the idea of increasing system safety through arc detection, KOSTAL developed the protective arc detection function for the PIKO 7, 8.3 and 10 kW inverters. Here, the voltage and current curve is measured over a certain period of time and evaluated by digital signal processing. If a characteristic typical of arcing occurs, the inverter immediately stops the current feed-in to the house grid. Perceived as a pioneering achievement at the time, this device feature reappears in future series.

2013: PIKO FUTURE – the first inverter family

Thanks to the innovation of the PIKO device, KOSTAL launched an entire inverter family onto the solar market with the PIKO FUTURE. The PIKO FUTURE allowed installers to reliably design small, medium-sized and larger systems using four correspondingly powerful solar inverters from 3 to 20 kW.

The inverter family covered a wide range of requirements. Single-phase smaller PV systems were catered for as were three-phase solar systems. The versatile design for these series was completely new. This meant that the PIKO FUTURE could handle larger currents and featured two network interfaces to enable interconnected operation. The complete system met many customer requirements and remained true to the KOSTAL philosophy of being able to offer flexible solutions with intelligent products.

2013: PIKO BA – the first hybrid inverter with high-voltage battery

With the PIKO BA, KOSTAL delivered another impressive inverter innovation for the photovoltaic industry. The idea was to achieve greater performance by connecting up a battery storage system and so the PIKO BA was born on the PV market. It was the first KOSTAL hybrid inverter with a three-phase connection option and a bidirectional DC input for a high-voltage battery. KOSTAL even received the ees Award for this inverter at Intersolar 2015.

The hybrid inverter set new standards in all areas. It offered three power classes with 6, 8 and 10 kW and the option of emergency power supply in the event of a malfunction or failure of the supply network within a changeover phase of 20 seconds. Another feature was a high-voltage battery with 228 V nominal voltage. It was based on a lead-gel structure from Hoppecke, which was a highly unusual practice for the time. In 2015, it was replaced by the lithium solution PIKO Battery Li. And lithium iron phosphate was deployed, something that has now become a common technology.

The high-voltage storage solution included several outstanding features. It created ideal conditions for greater power processing at a higher voltage, lower currents and smaller cable cross-sections. In addition, the efficiency of the battery could be adjusted via a management system and could later be easily converted to a lithium storage unit, which had become affordable in the meantime.

This is where the cornerstone for the trend towards electric mobility was laid because it became the order of the day to be able to provide high-voltage systems for electric vehicles with an inverter, storage solution and a compatible wall charging station. So KOSTAL deployed the PIKO BA as the market demanded. Anyone needing a powerful and efficient inverter was very well catered for, could run a battery immediately or at a later date and could control the power efficiently. That was incredibly innovative for its time.

The same applies to the device monitoring, which again was unheard of at the time. Home consumption and self-sufficiency could be checked and displayed by sensor. For example, the free innovative KOSTAL Solar Portal (called "PIKO Solar Portal" between 2010 and 2020) provided all the inverter's data at a glance and the device delivered maximum efficiency by eliminating the AC/DC conversion stage in the storage process and intelligent surplus charging.

2016: PIKO MP – the single-phase all-round inverter

The exciting concept of creating a hybrid function for single-phase PV operation was achieved with the launch of the flexible PIKO MP inverter. The device started as a single-phase converter with 1.5 to 4.6 kW and in its later PIKO MP plus variant from 2019 provided the option of connecting up a storage unit of up to 5 kW.

KOSTAL’s reliable and powerful compact device met the huge demand seen in the single-phase PV system sector. As a solar inverter, battery inverter and hybrid inverter, the PIKO MP plus inverter was versatile when used in conjunction with the highly efficient KOSTAL Smart Energy Meter.

2017: PIKO 36 EPC – the first KOSTAL project inverter

KOSTAL added to its product range the first three-phase inverter specially designed for the project business. With six DC inputs, an MPP tracker and 36 kW AC power, the device therefore closed the gap in the PIKO family and, as another product component for the classic private customer base, for the first time ever served the specific project market segment.

KOSTAL understood very early on that the power requirements of inverters would increase hugely in the coming years. Therefore, in 2021, the company introduced the commercial project inverter called PIKO CI, which can now be flexibly designed to work on its own and offer a higher output in interconnected operation.

2018 PLENTICORE plus – the hybrid pioneer

The idea behind the PLENTICORE plus device was as exciting as it was innovative. It is a modern and highly efficient solar inverter with 3 DC inputs based on a Linux communication platform, which can be used flexibly in string design thanks to its wide input voltage range. Alternatively, it also works as a hybrid inverter with two inputs for photovoltaic panels and a bidirectional battery input for a high-voltage battery. This offers maximum flexibility for installers and plant owners.

Its efficiency makes the PLENTICORE plus cost-saving and it is extremely flexible thanks to add-on performance features such as the battery connection. If required, an activation code can be purchased to activate the desired function. So customers benefit from only paying for functions that they really need.

A smart KOSTAL inverter through and through: self-learning shadow management as well as future-oriented pre-equipped interfaces for sector coupling and open communication with third-party providers, e.g. for Smart Home connection.

The PLENTICORE plus set market standards and stepped onto the winner's podium in its first storage tank inspection. The following year, it again took first place, impressively demonstrating its exceptional energy efficiency. The PLENTICORE plus has become the benchmark for efficient storage systems.

It is available in various power classes between 3 and 10 kW and is ideal for roof areas of between 3 and 15 kWp. All this in a single and compact design. If required, it can also absorb the energy of other inverters via the AC side and store it in a connected battery.

Since its market launch, the KOSTAL hybrid inverter has repeatedly demonstrated the highest levels of efficiency and features energy management including free system monitoring via the KOSTAL Solar Portal and an optional auto-update function. In addition, the PLENTICORE plus can supply powerful consumers such as the wallbox or a heat pump in a compatible and simple manner.

2019 KOSTAL Smart Energy Meter (KSEM) – the first intelligent energy meter

The KOSTAL Smart Energy Meter (KSEM) is the company’s response to customer demand for additional control options for them to optimise energy in their homes. It can be used, for example, to allow a KOSTAL PLENTICORE plus to independently distribute energy in the house with or without a battery being connected.

Coupled with the PIKO MP plus, the KSEM handles internal energy management, including additional storage unit control, in order for energy generated and not directly consumed to be used at a later date.

For system configurations of more than 63 A, e.g. in combination with the PIKO CI, the KOSTAL Smart Energy Meter provides the option of using external measuring transformers so that the PIKO CI can also use the data to control itself.

Other functions, such as recording several KOSTAL inverters for controlling and visualising home consumption in the KOSTAL Solar Portal as well as the provision of data for external components via Modbus and SunSpec, e.g. for external energy managers or private applications, round off the diverse ways in which the KOSTAL Smart Energy Meter can be used.

But the KOSTAL Smart Energy Meter can do more than just serve emerging needs. With the introduction of future functions in mind, such as activation of a wallbox, including consideration of solar charging modes, the developers have enabled the energy manager to also serve as the control unit of the ENECTOR AC 3.7/11 (2022) right from the outset. Scope to expand the overall concept has always been the focus of the product and so far there have been no limits on further features.

2020 PLENTICORE BI – the first KOSTAL battery inverter for storage units

The innovative concept of the battery inverter continued to impress plant owners who operate a solar system and now want to retrofit a battery for storing PV power as they need a powerful and intelligent battery inverter that can store surplus solar power in storage units on its own and in a network.

The market got the efficient specialist device it had long wanted in the form of the PLENTICORE BI. A battery inverter that creates independence: 5.5 and 10 kW, suitable for private use and impressively powerful for commercial customers. The PLENTICORE BI is compatible and easy to deploy in existing solar systems to effectively increase self-consumption and self-sufficiency. With 10 kW charging and discharging power, storage units with up to 66 kWh can be operated reliably and efficiently today.

2020 PIKO CI – the first inverter family for the commercial sector

As the energy transition progresses, KOSTAL launches exactly what is needed at exactly the right time: a large-scale project inverter that can serve ever higher power demands and PV power capacity requirements.

Performance features include optimisation for outdoor use, reliability through weather resistance, variability in string design with up to four MPP trackers and operational safety thanks to integrated overvoltage features. To cut costs, the engineers designed the integrated Smart Switch, which eliminates the need for an external circuit breaker up to 135 kW.

The PIKO CI is compatible with other devices and very powerful. Its interfaces ensure that it works efficiently in multiple-inverter operation and at the same time is easy to set up, update, check and modulate with a mobile device via the PIKO CI app using WLAN and online communication.

Future-proofing is also an important feature of the PIKO CI: the device is already set up for further growth in power demands and can therefore serve an increasing PV power demand – optimum power generation on a large scale too.

2022 ENECTOR – the first AC wallbox for electric vehicles

KOSTAL Automotive Electrical Systems has been developing vehicle components for a century. Combining this expertise with that of KOSTAL Solar Electric and designing a product to unite both areas was therefore the obvious next step and resulted in the AC wallbox ENECTOR AC 3.7/11. Awarded the German Design Award for its elegant appearance, it supplies a maximum of 3.7 kW or 11 kW in one to three phases with a current of up to 16 A per phase. Alongside outstanding form and function, it doesn’t fall short in terms of convenience either. The LED display indicates all important status messages and the charging status, while the 7.5-metre-long charging cable offers sufficient flexibility for even greater distances from the charging point (e.g. for a double garage).

In combination with the KOSTAL Smart Energy Meter, this presents the user with various intelligent and, above all, efficient vehicle-charging options. For example, it allows energy to be fed in from various sources (direct feed-in, battery, grid) in varying proportions. Management is covered by the KOSTAL Smart Energy Meter, the KOSTAL Solar App and the KOSTAL Solar Portal.

2022 and beyond – what the future will bring

KOSTAL will continue to inspire its customers with innovative and market-leading solutions.
This year, KOSTAL is launching its own AC wallbox. In combination with the KOSTAL Smart Energy Meter and the right activation code, the wallbox impresses customers with its exciting convenience features.

In addition, new functions are being continually added to the existing inverters, such as the higher input current for the PIKO CI commercial inverter or the communication enhancements for the PLENTICORE plus hybrid inverter. A completely new generation of inverters with exciting innovations is also waiting in the wings.

In order to bring innovations to market in series production, KOSTAL has been involved in research projects ever since its very first inverter. Currently, for example, work is already being undertaken on bidirectional DC wallboxes and corresponding applications.

Shaping the energy transition together – with KOSTAL, the future remains exciting.