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  • Writer's pictureEmil Kormosz

How does a hybrid inverter work and why is it an investment for the future?

Updated: Aug 25, 2023


photo of inverters installed in a row at the back on a photovoltaic panel structure in the field and you can see some sky

Introduction


We would like to discuss an increasingly relevant topic, which is the energy situation in Europe and around the world. Lately, we hear more often about power outages, drastically rising energy prices, and bans on the use of traditional heating sources. Therefore, it's worth considering whether to invest in photovoltaic installations equipped with a hybrid inverter. What is it? How does it work? Is it worth investing in? We will try to answer these and many other questions in today's article.



What is a hybrid inverter?


Common definitions describe it as a smart device that combines the functions of an inverter, solar controller, and energy charging controller. In simpler terms, the hybrid inverter's task is to convert DC current into AC current, cooperate with a compatible energy storage, and intelligently manage stored energy. At this stage, we are not aware of any hybrid inverter that doesn't possess these features. Of course, inverters and their energy storages differ in parameters and the discharge level of the storage, but more on that later.



Three hybrid inverters from fronius, solplanet and solaredge

How does the inverter behave when there's a power shortage in the grid?


But what happens when the grid runs out of power? How do inverters behave then? By asking this question, we put some hybrid inverter manufacturers in an awkward position. For the average "Smith," spending often tens of thousands more on a hybrid inverter and energy storage, the answer seems obvious: "The inverter starts converting DC current from the energy storage and begins to supply the network in our home as a backup." This answer, although seemingly reasonable, isn't entirely true.



photo showing the flow of energy through the inverter with the example that the energy goes from the PV modules to the inverter from the inverter to the consumers and energy storage

Inverter manufacturers worth getting acquainted with.


Let’s get down to specifics and focus on selected manufacturers with whom we collaborate.


Solar Edge hybrid inverter shown

One of the most popular and respected inverter manufacturers is SolarEdge. They have hybrid inverters in the RWS series in their offer. This series is compatible with the SolarEdge Home 48V energy storage. This allows for the installation of a storage unit with a capacity ranging from 4.6kWh to 23 kWh. The inverter works flawlessly when there's power in the grid, converting DC current, charging the energy storage, and cooperating with the SolarEdge optimizer and the SolarEdge meter. However, when there's a power outage in the electrical grid, for instance, due to network failure or deliberate power cuts, the inverter goes into sleep mode. The stored energy in the storage unit becomes useless, as the inverter doesn't switch to backup mode. The manufacturer shrugs it off, explaining that the product specifications state the lack of Offgrid operation and backup. However, when deciding on an inverter with storage, this is not the answer we're expecting...

Another hybrid inverter series, which will likely be available this year, is the RWB48 hybrid inverter. It is expected to have off-grid functionality. However, keep in mind that to activate this feature, you need to purchase an external SolarEdge Home Backup Interface device. An immediate question arises: why isn't this all in one device? After all, this series is designed for backup purposes. We couldn't get a clear answer from the manufacturer. We can only guess that when the purpose isn't clear, it's probably about... The product is so new that there's currently no additional information available.


show white hybrid inverter from Kehua company

In contrast, let's look at a relatively new manufacturer in the Polish market producing hybrid inverters, Kehua. They have launched hybrid systems named ISTORAGE 3. An interesting feature is the location of the inverter as an overlay on the battery. This gave the product a modern look, and it also eliminates the need for additional cables connecting the storage to the inverter. By default, the inverters have a backup option. You can allocate a specific circuit for emergency power or supply the entire home distribution board. Remember, in the case of emergency power, the inverter operates with its nominal power divided into 3 phases, and if one phase is overloaded, the inverter might shut down. A safeguard to reduce this risk is to allow a phase overload of 100% power for up to 60 seconds. Installing batteries and connecting them involves stacking them, with up to 3 battery modules of 5 kWh each in a single column. Importantly, the storage can be expanded at any time (the degree of wear of old batteries doesn't affect the efficiency of the new battery). A noticeable downside may arise during the installation of panels that require optimization. Currently, the inverter isn't compatible with optimizers.


Fronius hybrid inverter and energy storage shown

Let's move on to another manufacturer — Fronius and inverters from the SYMO GEN24 plus series. These are the latest hybrid inverters, offering emergency power either by allocating a specific circuit or by what's called Fullbackup, powering the entire distribution board in the building. For Fullbackup mode, apart from the Fronius Symo GEN24 plus inverter and a compatible BYD or LG energy storage, we need an energy meter and a backup switch. There's the option to purchase dedicated distribution boards that contain the aforementioned components, but expect a cost of several thousand zlotys. A drawback of Fronius inverters, just like Kehua, is the lack of dedicated optimization.


Hybrid inverter in blue from Solplanet

Our last recommendation for hybrid inverters in today's article is the Solplanet company's inverters. On the Polish market, there are 3 power ratings of these inverters constantly available - 8,10, and 12 kW. The integrated storage is the Pylontech storage. The inverter is also compatible with Tigo optimizers. However, to observe the operation of optimization, it's necessary to purchase an additional gateway that collects optimization data. The manufacturer equipped inverters with two backup outputs during emergency power. One input can operate with a maximum nominal power of the inverter, the second input has this power limited by half. However, remember that the total power at the backup output cannot exceed the inverter's nominal power. Although the manufacturer also allows emergency power for the entire distribution board, it's worth paying attention to the power of the receivers, because if one phase exceeds its power, the inverter will shut down. The allowable power for one phase is calculated using the formula: inverter power/3. It's worth considering whether, in such a case, to install a larger inverter to have a higher allowable phase power. Of course, there's a trade-off; an undersized inverter will result in production losses, but it offers more flexibility during backup power. We'll leave the answer to you.


In the table below, we present a comparison of the described inverters. Apart from the price, it shows that you should consider several other important aspects to choose the most optimal inverter for your needs:

Manufacturer

SolarEdge

SolarEdge

Kehua

Fronius

Solplanet

Inverter series name

RWS

HUB24

Istorage 3

SYMO 24GEN plus

Compatible storage

SolarEdge Home 48V

SolarEdge Home 48V

iStoragE

BYD

Pylontech

Off-grid capability

None

Exists

Built-in backup output

Exists

Built-in 2 backup outputs

Additional components to activate emergency power functions

This function is not available

​SolarEdge backup

In the case of separated circuits, no additional components, in the case of supplying the entire switchboard, the emergency switch.

In the case of activating the fullbackup function, a switchboard is needed along with a dedicated meter.

In the case of separated circuits, no additional components, in the case of supplying the entire switchboard, the emergency switch.

Optimization

SolarEdge

SolarEdge

None

None

Tigo

Additional costs for optimization

None

None

None

None

communication Cloud

Additional costs

Connection cables between battery and inverter

Connection cables between battery and inverter

None

None

Connection cables between battery and inverter

Possible storage expansion

Probably yes

Probably yes

Yes

No

No

Price ranking (1-worst)

2

1

4

3

5

We hope that our article today has helped clarify what a hybrid inverter is and its capabilities. It's worth carefully considering and thoroughly analyzing the decision to invest in this device in terms of your own needs and financial capabilities.


Looking for a better solution for your home or business? We will help you choose the best!




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