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Fronius Inverter ReviewIt’s no overstatement to say the Fronius Primo inverter and Fronius Symo inverter has a cult following in the Australian solar market. But does the Fronius Inverter deserve its reputation? Before scrutinising the inverter, we’ll start with a brief history of the company Fronius. We’ll then have a glimpse at the mothership, Fronius International, and I’ll introduce the Fronius Australia team.

After the fluffy stuff, we’ll look at the design of the Fronius SnapINverter series. We’ll look under the hood of the Fronius Primo, and I’ll reveal our failure rate.  I’ll then explain why a soon to be released Fronius Primo SC is actually the good old Fronius ‘International’ with a fancy name. We’ll discuss the limitations of some of the Symo inverters, and we’ll wrap it up by looking at Fronius Solar Web and the Fronius Smart Meter.


Fronius; the company

Günter Fronius

Günter Fronius started Fronius in 1945 – the same year World War 2 ended. He began by building battery car chargers in his family home in Rankleiten, Austria. In 1950 he applied his DC to AC conversion expertise to manufacture welding transformers. In the 1980’s he handed the business over to his children, Bridget and Klaus, who drove the vision of Fronius internationally.

  • In 1992, Fronius introduced a third division, Solar Energy.
  • In 2001, they made the now infamous Fronius IG inverter.
  • In 2014, they made amends for their IG inverter mishap and brought out the Fronius Primo and Fronius Symo inverters.

That’s how it all began.


Fronius International

Mrs StraussLast year I was invited to Fronius International and had the privilege of meeting the Grandaughter of Gunter Fronius and CEO of Fronius International, Mrs Strauss. It turns out you don’t get to know an Austrian businesswoman in a 2-minute chat. But judging by the way her Fronius Australian staff speak of her, she’s something special.

Although the company now has a huge international presence, it has kept its family business feel thanks to the warm and wise leadership of Mrs Strauss. Fronius radiates a positive, professional and friendly atmosphere.

Fronius International

Fronius perfectionism

The tour of Fronius Austria was impressive. Having previously lived in Austria I am acutely aware that Austrians are prudent and orderly people who respect perfectionism. This is interesting if not intimidating to witness in the day to day life, but to see this translate into a large-scale Research and Development Facility and Manufacturing Plant was mind-blowing. Understandably, photographs from inside the facility were not permitted. But I can share a glimpse into how impressive the facility is by sharing one of their marketing videos.

Before I visited Fronius International, I assumed these promotional videos were cleverly imagined and fabricated marketing material. Apart from the golden British voice over and the slow-motion strutting, it is a close reflection of reality at Fronius Research and Development.


Fronius Australia

If the culture of a business is a barometer of its longevity, then Fronius Australia is here to stay. I’ve had the privilege of travelling and working with many of the key Fronius Australia staff over the last few years. Keshia, Adrian, Rod, Bella, Balaji, Sebastian, and the new player in Brisbane, Matthew, to name a few. They stand apart from their competitors. You can tell they love working for Fronius, and were picked for their passion and knowledge of the industry. It’s always a pleasure having a meeting or a beer with any of them.

So an Austrian family business starts out in the dust of World War II and builds an international empire with an amazing company culture and a hunger for perfection. The fluffy stuff sounds A-OK. But is the inverter any good?


Fronius inverter review


The Fronius SnapINverter (as it is cleverly and uncommonly called) is smart and sleek. You can’t say that about every inverter. To comply with Australian Standards, Fronius integrates the DC Isolator onto the backplate so we don’t have to install another DC isolator beside the inverter. The integrated DC isolator not only saves on install time and material cost, it also makes the install neater (ignore the conduits all over my test wall). The inverter then “snaps in” to the back plate. Shmicko. Easy and good looking install. Everyone is happy.

The only other inverter that integrates a DC isolator that is compliant with AS 5033 is SolarEdge. However, the SolarEdge design is far from elegant.


Fronius Primo internalFronius internal build

The Fronius inverter is an obvious product of an anally retentive production line manager. I’ve pulled apart a few inverters in my time, and I don’t think it’s just my bias that says the Fronius inverter is the neatest. You don’t get the silicone like goop smeared all over inverters, and all wiring is neatly loomed.

I watched the assembly process when I visited the factory in Austria. It was impressive how each one was assembled by the hands of attentive Austrians who didn’t look to be in a rush.


Fronius coilHowever, I did find one thing that proves beyond reasonable doubt that Austrians are not perfect. An inductor coil on the 18 amp Primo is separated from the other inductors with a piece of imperfectly wrapped insulation!

Yeah, that’s the best I’ve got.




Fronius external fan

Fan Cooling

The 12 amp Fronius Primos have one external fan, while the 18 amp versions have two. All Fronius inverters also have an internal fan. High temperatures shorten the life of electronics, particularly electrolytic capacitors, so it is vital to keep inverters cool.

As seen in this thermal image, the Fronius inverter does a particularly good job at pumping hot air out of the top of the inverter. The ABB inverter on the right only uses an internal fan. SolarEdge and Huawei don’t use a fan at all. These manufacturers might argue that the external fans are exposed to the elements and prone to failure. After three years and 1600 installations, we haven’t had an issue with a Fronius fan. And after seeing first hand the lengths Fronius International go to with accelerated testing, I feel no reason for concern.

Warranty Claims

In reality, every electronic device has a failure rate. In the solar industry, a failure of less than 1% is acceptable. Fronius don’t tell us specifics on their failure rate, but they aim for less than .5% and say they reach that target with most of their products. All products are under 1%.

But let’s not take their word for it. After installing about 1600 Fronius inverters in three years here are our approximate failures:

Dead on Arrivals (DOA):

  • Inverters DOA:  4 out of 1600 or .25 per cent
  • Smart Meters DOA: This is mainly screws stripping in the terminals.  12 out of  1030 or 1.7 per cent.
  • Data Manager Cards DOA: 4 out of 1600 or 0.25 %

If you added all the DOA issues together, we have 20 jobs with some kind of DOA. Or a whopping 1.25% of jobs. However, DOA’s are just an annoyance to the electrician on the day of installation – it does not affect the system uptime.

Failure after installs

  • Inverters failure after installation: 5 out of 1600 or 0.31%.
  • Data Manager Cards after installation: 3 out of 1600 or 0.18%
  • Smart Meter failure after installation: 3 out of 1030 or 0.29%

If you added all the failures together, we have had 0.68% of jobs that we have had to return to. But again, Data manager Card and Smart Meter Failures do not affect system uptime.

The all-important failure rate that affects uptime is just the inverter failures after installation, which is 0.31%.


The Fronius Primo Power Stack

The power stack is where the DC to AC conversion happens. It’s what replaced the transformer in old inverters to make inverters transformerless. The Fronius power stack uses H5 Bridge technology (a technology that SMA introduced into the market) which switches five transistors (in the form of an “H”) to chop up the DC into a 230v AC output. Fronius uses two different power stacks for their Primo inverters.

5kW Fronius Primo with 12amp Power Stack

Fronius Primo with 12 Amp Power Stack

The smaller power stack is only capable of handling 12 amps per input and are used in the Primo 3.0, Primo 4 and the Primo 5.0 (otherwise known as the Fronius “International.”)

The 12 amp power stack has fewer electrolytic capacitors, inductors, transducers and film capacitors. Because it is only rated to 12 amps, it means (at least on paper), we can not put 2 strings (or groups) of panels into 1 input. This isn’t an issue with smaller inverters when we only used 16 panels, but it becomes restrictive when we want to install 24 panels on the Primo 5 International.

Fronius Primo international

Fronius Primo with 18 Amp Power Stack

When we install more panels, we need higher current so we can install 2 strings of panels into 1 input. The 18 amp powerstack is used in the Primo 5.0 AU, the Primo 6, and the Primo 8.2.

The Primo 5.0 AUS has a nominal output of 4.6kW. It was introduced to Australia because, in some parts of Australia, red tape limited the size of an inverter to 4.6kW. CEC guidelines state we can only install 33% more panels than the nameplate of the inverter so the Fronius 5.0 AUS is limited to 6.1kW of panels.

The Fronius “International”

In parts of Australia that allowed a full 5kW inverter, the 5kW Fronius International became popular because it meant we could install 6.6kW of panels. (The Fronius 5.0-1 is not technically called the “Fronius International”, that’s just the name the industry adopted to differentiate it from the Fronius 5.0-1 AUS.) A poorly kept secret was that the Fronius International was actually made with the 18 amp powerstack. So while on paper we could not install 2 strings of panels in 1 input, in reality, we could. It worked well and it was compliant.

However late last year we got some devastating news. The Fronius International was going to be made as per the spec sheet, with the 12 amp tracker. But the devastation was short lived. Fronius heard our cry and introduced the new Fronius SC. SC stands for Superior Current. The name is uncharacteristically tacky of Fronius, but we’ll learn to embrace that and for now, we’ll celebrate that we got our baby back. A full 5kW nominal inverter with an 18 amp power stack!

So now we have three different 5kW Fronius Primo inverters:

  • The Fronius Primo AUS (18 amp, 4.6kW nominal, 6.1kW input)
  • The Fronius Primo “International” ( 18 amp 12 amps, 5kw nominal, 6.6kW max panels)
  • The Fronius Primo SC  (18 superior amps, 5kW nominal, 6.6kW max panels.) Available Q3 2018.

Fronius Symo

The Fronius Symo is sometimes not as flexible as we would like. The Fronius Symo 5kW, 6kW, 7kW and 8.2kW inverters are limited to 16 amps. If we want to parallel two strings of standard ≈9 amp panels into 1 MPPT of a Fronius Symo, we can, but with a poor design: we would clip the maximum power of that MPPT input.

Fronius produced a whitepaper that explained that “current oversizing” leads to annual losses of less than .75 per cent. The problem is, that study was done in Munich, which sees even less sunshine than a sheep in a paddock on the southernmost tip of New Zealand. However, I figured I could adapt the logic in sunny Brisbane with a few tweaks:

  • If we parallel 9.3 amp panels east and west, the panels wouldn’t max-out at the same time, so they would be less likely to reach 16 amps.
  • If we are oversizing the inverter by 33%, the current would only be limited when the power is limited.

Because of my flawed logic, a few of our solar 8.2kW Fronius Symo systems went out with a parallel string design. When we looked back into the Fronius SolarWeb monitoring we found this:

The problem with my logic was this:

  • Even east-west paralleled strings in Brisbane would come close to their specified operating current at the same time, and,
  • We normally did not significantly oversize 6, 7 or 8.2kW inverters, because we could instead just use the bigger inverter.

For the record, we rectified our mistake by simply replacing the 8.2kW Symo inverters with 10kW Symos.


The Fronius Screen

The Fronius SnapInverter may be one of the last inverters to have a screen. Most manufacturers are moving away from using inbuilt screens because of reliability issues. Instead, they are heading to online monitoring or connecting directly via your smartphone. I prefer a screen as a backup because passwords will be forgotten and it could complicate what could have otherwise been simple troubleshooting. However, in the ideal world, every inverter would be monitored online.

Fronius Solar Web

Fronius Solar Web ( is the Fronius online monitoring platform. It’s a poor reflection of the solar industry that less than 50% of Fronius inverters were ever connected to SolarWeb. Shame on you cheap-arse sales companies for delivering a half-arsed install. Connection to Solar Web should be essential. If you have a Fronius inverter that was never connected to Solar Web, an earth-fault alarm may need to be installed to meet CEC regulations. Chances are, that didn’t happen. So call your installer and give ’em what for.

Connection to Fronius Solar Web gives you an easily navigated phone-app or web-browser so you can see:

  • Instantaneous solar production
  • Instantaneous household consumption (if you install the Smart Meter)
  • Day, Month, Year, Total production data in a simple and clear format.
  • Overlaid historical consumption if you install the Smart Meter.

Fronius also goes much deeper for the installer with:

  • Historical AC voltages on each phase
  • Historical DC voltages on each tracker
  • Historical DC current on each tracker
  • Historical AC current

Having the ability to diagnose issues like high grid voltages or seasonal shading, or even just the ability to confirm panel stringing, is a huge advantage for both us and our customers.

A simple hack of the Fronius Solar Web is that you can currently get the Premium version for free. When you are logged into your Fronius Solar Web account, sign in as if you are going to pay, but when it asks you for payment, the balance owing is zero. Once signed up to premium, your historical data is extended from 3 days to unlimited. This may change in the future to require a payment, but for now, it’s completely free.


The Future of Solar Web

From my bias, Fronius offers the best monitoring of any inverter. But in keeping with their “shifting the limits” motto their pending revamp will include:

  • The ability to compare what your system is producing to what your system should be producing using seasonal data and current weather data.
  • A battery sizing tool.
  • Multiple Smart Meter monitoring so we can monitor your new Fronius and your existing inverter on the same platform. And for the “Jack Longy Longs” of this world who want to monitor everything.
  • Sorting abilities for companies with thousands of installs.
  • A simpler way to work out your electricity bill over specific dates – keeping your energy retailer honest!


Fronius Smart Meter

The Fronius Smart Meter is the pièce de érsistance of Fronius Solar Web. The Fronius Smart Meter is a small device that we install at your switchboard to measure the power that you consume from and sell back to the grid.

All you have to do is open the Fronius Solar Web app or log in to Solar Web online. I explain more about the Fronius Smart meter in this post.

It should be noted that you only get a 2-year warranty on the Fronius Smart Meter, and Fronius do not manufacture it themselves, which kind of takes the shine off it.




If I didn’t make it clear, I’m a Fronius fanboy, but for good reason. Fronius has a solid history and an impressive Austrian manufacturing facility. The Australian team reflects the culture that Gunter Fronius began and his granddaughter continues. Austrian perfectionism shines through in the build of their inverter. If needed to find fault, you could speculate that external fans, inbuilt screens, and Smart Meters may have issues in the future, but after seeing how Fronius does their accelerated testing, I think we’re pretty safe with the fans and screens. The Fronius Primo lines up every version you would want, crowned by the versatile 5kW Primo SC. While the smaller Fronius Symo can be restrictive, those restrictions can be overcome by using a 10kW Fronius Symo. Fronius Solar Web is the best and getting better, and the smart meter is the icing on the cake.

If you are looking for a quality solar system in South East Qld, contact us.


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5 Comments on "Fronius inverter review"

5 Comments on Fronius inverter review

Mark C said : administrator Report 2 days ago

Hi Mike. The short answer is no. If you buy a Fronius Primo now and want to get a battery later, then you would either swap your inverter for a hybrid inverter, or you would install a AC coupled battery (like Tesla PowerWall). Installing an AC coupled battery is probably more practical. Getting a Battery ready inverter now, (for a battery that you may buy in 2 years) is like buying a phone charger today for a phone you may or may not buy in 2020.

Mark C said : administrator Report 2 days ago

Hi Will. If there are too many panels to put in a string, you would need to parallel otherwise the voltage would get to high. (EG 16 panels north, and 6 east). Or if panels are facing different orientations (eg 8 east, 8 west and 6 north.). This blox explains it a bit better.

Mike Chapman said : Guest Report 2 days ago

Will Fronius make a board swop for the Primo when you want to install batteries in due course?

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K. Markham. said : Guest Report 2 days ago

Great review and well written, its nice to have my choice validated by someone who knows what they are talking about.

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Will said : Guest Report 3 days ago

Hi Mark, Why not just split the 24 panels into two strings of 12 each since the Fronius 5kw comes with 2 MPPTs? I know it is not as simple as that and there must be a good reason why someone would want to put all 24 into one MPPT. Appreciate if you can explain the details. Thanks heaps! Cheers, Will

  • 3305

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Hi Mark, Why not just split the 24 panels into two strings of 12 each since the Fronius 5kw comes with 2 MPPTs? I know it is not as simple as that and there must be a good reason why someone would want to put all 24 into one MPPT. Appreciate if you can explain the details. Thanks heaps! Cheers, Will

K. Markham.

Great review and well written, its nice to have my choice validated by someone who knows what they are talking about.

Mike Chapman

Will Fronius make a board swop for the Primo when you want to install batteries in due course?

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