Fronius Solar inverter review

Fronius Symo image

Fronius Solar Inverter Review Australia - Updated April 2021

Fronius are the 12th largest solar inverter manufacturer in the World.

All Fronius inverters are designed and made in Austria.
Fronius inverters have a proven record for reliability.

The Primo (single phase) and Symo (three phase) 'snap' inverters have been with us since 2013, and it's a testimony to how good these products have been that they remain the top selling inverters in Australia a remarkable 8 years later. "If it ain't broke, why fix it?"

Fronius DO have some new products now.
The Primo and Symo will carry on, no doubt for several more years, but the new Fronius range of single and three phase GEN24Plus is mostly what this review is about.

Fronius have retained the Primo and Symo names so the new inverters are the Primo GEN24Plus and the Symo GEN24Plus.

The Primo GEN24Plus
They are single phase inverters that are hybrids that can connect to battery storage.

There are various models from 3kW to 6kW, but in Perth, 5kW will be the top seller by far.
It is compatible with BYD high voltage HVM and HVS batteries, and it is hoped that by the end of 2021, the new LG Chem range of batteries will also be supported.

The 5kW model sells for $3,355 which is $1,175 more than the regular 'Primo 5kW' and double the price of its most serious competitor.

The Symo GEN24Plus
There are two versions of this 3 phase hybrid inverter, so it is important to understand the difference.
The 3kW to 5kW models are different to the 6kW to 10kW version.
I very much doubt we will ever sell anything other than the 5kW model in the smaller range, so I'll focus on that first.
This is a 'cut-down' version of the larger 6-10kW models and is therefore quite a bit cheaper BUT it lacks one feature.
It does not have back-up.
Further down I explain PV Point and Back-up, and this 5kW three phase model does have PV Point, but will never have back-up.
If you want back-up then you must go for the 6kW to 10kW range.
We are waiting for pricing on the 5kW model, due May/June 2021, but the 6kW is $4,200.

I expect the 5kW, as it does not have the cost of back-up circuits, to be about the same price as the 5kW single phase model at around $3,355.

The 6-10kW models deliver backup up of 3kW of power per phase with a 4.5kW per phase initial surge tolerance.

I'll explain the back-up features starting with PV Point.
PV Point is an RCD protected GPO (power outlet) that only works when the grid goes down.
You don't need a battery plugged into the Fronius, it can work directly from the panels.
Approximately 60 seconds after the grid fails, the inverter will re-direct up to 3kW of panel power to this outlet, so obviously, this only works during the day.
As long as whatever you plug into this outlet draws less power than the panels are producing, it will keep working, but if the load exceeds the panel output, it will trip, shut down the inverter and then the inverter will try and start up again a little while later.

The fact that a few passing clouds might end up reducing the panel output so the inverter shuts down renders this feature more into the gimmick category than anything truly useful, but it's a different story if a battery is connected.

If the battery is connected, then the PV Point can draw power from both the panels and the battery which will stabilise supply.

The second form of 'back-up' is what Fronius call 'Full Back-up'
The hardware needed within the inverter is included in the price, but does not include a contactor and relay (approx $250) that are needed in the switchboard to safely separate from the grid. Also there is the need for re-wiring the board to handle your essential loads, so when all is said and done, there's likely to be an extra $600 in parts and labour at the very least, to deliver this 'full back-up'.

So, when the grid goes down, after about 60 seconds, the inverter will switch-over to supplying up to 5kW of power to the 'essential loads' circuit.

This power will come from the battery and also the panels (if during the day).

What are these 'essential loads'?
There are a variety of circuits in your house. Power outlets, lights, your oven, Aircon etc.
5kW of backup power from a solar inverter and battery isn't going to be enough to power all of these so you have to choose.
"What do I want to work when the grid power goes out?"
Lights and outlets are the obvious choices, and not the oven, air con, pumps that will draw too much power.
It's not just the amount of power the inverter can send through, its also how long it can sustain it.
If you have a 10kWh battery and you are pulling down 5kW an hour, then the battery is empty in 2 hours, whereas if you keep the power use down to 1kW, you have 10 hours of backup from the battery, which might last you until the next morning when the panels will start up and then start to re-charge the battery keeping the back-up going almost indefinitely.

So the golden rule of power use in a blackout is turn on as little as possible.
Boil a pan of water on the gas hob instead of turning on the kettle. I'm sure you get the idea.

Here are some common questions and answers about Fronius solar inverters.

Are Fronius inverters battery ready?
The single phase Primo and the 3 phase Symo are NOT battery ready, but the latest GEN24Plus models are ready to connect BYD high voltage solar batteries and later, LG Chem batteries.

Are Fronius inverters noisy?
The existing Primo and Symo inverters are noisy, 65Db when the fans are working hard, but the new GEN24Plus models are much quieter at 44Db. Despite the very obvious fans visible in the front of the new GEN24Plus models, the better cooling and lower noise of the new generation models is due to better internal design and a far superior heat sink than the old models.
Our observation has been that the GEN24Plus fans rarely even operate, which rather proves the point that other inverter manufacturers have been making that passive cooling is very effective with a good design and heat sink.
It seems the fans on the GEN24Plus are really there for show.

Is Fronius WiFi reporting good?
The free version isn't all that great, but the paid 'Premium' version ($39 a year) gives most people what they want, and if it's not enough, there are APIs to export your solar data into other applications, although, again, there are limits to how much you can pull down for free before you start getting charged.

Can you oversize the new Fronius battery inverters with even more panels?
Yes, Fronius allow 150% oversizing, so the 5kW inverter can have 7.5kW of panels when a battery is connected.
I have asked Fronius as to why this oversize limit is so low, as Huawei and SolarEdge can oversize to 10kW of panels on a 5kW inverter with battery (200% oversize), but Fronius say they are sticking with 150% max.

Is the battery connection to the GEN24Plus DC coupled?
Yes it is. It's a true hybrid inverter capable of handling both panels and battery.
Western Power seem much happier with approving DC coupled batteries over AC coupled, especially when additional over-sizing of panels has been applied for.

Can the GEN24Plus inverters be AC coupled?
Yes. If you have an existing solar inverter, perhaps another Fronius, you can leave it in place to run the solar panels and then connect a GEN24Plus, single or three phase, to your switchboard with a battery plugged into it.

Unfortunately the two inverters, even if both are Fronius, can't talk to each other, and you can only have one consumption meter (which would go on the GEN24Plus), but the AC power from the solar inverter will first power the house, and then flow to the second inverter to charge the battery.

What is Fronius Multi Flow Technology?
Multi Flow Technology means that the inverter can manage energy flows in all directions.
It can simultaneously accept DC power from the solar panels, store panel power into the battery or release battery power to the house.
It is what ALL solar + battery inverters do, not just Fronius, but it's a very good name to describe the function.

What is Fronius SuperFlex Design?
It means you can have three strings of panels, two of them in parallel.
Let's say you wanted to install 18 x 370W panels (6.66kW)
You could have a string of 6 facing East for the morning sun, a second string of 6 facing North, and a third string of 6 facing West for the afternoon sun.
Two of those strings would be connected together, say West and East, on one of the inverter MPPTs and the third string on the other MPPTs.
There are a couple of drawbacks with doing things this way with some losses due to West and East hitting their straps at different times of day so one string is continually pulling the other down a bit, but it's only a few percent overall.

It is however a feature that comes much more into play with larger (8-10kW) inverter design.

Fronius Primo (single phase) brochure

Fronius Symo (three phase) brochure

Fronius Primo GEN24Plus hybrid brochure

Fronius Symo 6-10kW GEN24Plus hybrid brochure

Fronius Symo 3-5kW GEN24Plus hybrid brochure

This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.







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This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.