Fronius Gen24 Review

The much-anticipated award-winning Fronius Gen 24 has finally hit the Australian Market. The Fronius Gen 24 is simply a new battery-ready inverter or hybrid inverter. Fronius gave me an early model Gen 24, which I’ve been testing for several months. In this post, I’ll first outline the features of the Fronius Gen 24, and how it does what many hybrid inverters can’t do. Next, I’ll reveal what really sets the Fronius Gen 24 apart – the build quality. Read on, or watch my summary in the video below.

What to look for in a Hybrid inverter and Battery

Not all hybrid batteries are created equal. The features that we’ll discuss below are.

• Batteryless backup – A great feature if you are looking to install solar now and a battery later.
• Brand reliability and warranty (forget your warranty if the brand isn’t reliable).
• Brand compatibility.
• Battery Size. Do you have enough storage to keep you going overnight?
• Excess solar. No point in having a huge battery if you don’t have enough excess solar to charge it.
• Changeover time. How long does it take to change from on-grid mode to blackout mode?
• Blackout mode. What will the inverter and battery actually do in a blackout?
• AC coupling. Use your old solar system to charge your new battery.

But before we even discuss batteries, let’s talk battery-less.

Update 20/04/2022 – New “peak demand” charges / penalties have started to show up on Queensland power bills and they look like they’ll become the new normal. If you’re getting these charges already or just want to be prepared for when they change your plan. Solar Batteries could be a good option. You can check out our BYD battery pricing page here.

Batteryless backup – Gen 24 PV point

With the Fronius Gen 24 you can now have power in a blackout without a battery. Fronius cleverly call the feature “PV Point”  (PV = solar power). I call it Batteryless Backup.

PV point is not a perfect solution. It will only operate when the sun is out, and it won’t back up your whole house. Instead, we install one dedicated power point next to the inverter or in your house. That dedicated power point will only turn on in a blackout. In the event of a blackout, you’ll need to run an extension lead to your fridge.

The PV point will output a maximum of 3000w, so as long as your solar is producing at least 3000W you could easily run a fridge, a deep freezer, charge your phone, run a computer and have some left over. It could run an electric frypan, a toaster and a kettle. Just not all at the same time.

Some think PV point is a gimmick. I think it’s pretty cool. You can get halfway to being blackout-proof without forking out big bucks for a battery. And to be honest, that’s why I’m most excited about the new Fronius Gen 24. It’s an affordable closet-prepper backup solution now, and it’s a true “battery-ready” inverter.

What does battery ready mean?

Battery-ready is a misused term. You can plug a Tesla Powerwall into any inverter, but that doesn’t make the inverter that you plug it into a “battery-ready inverter”. Battery-ready is a term that should be used for DC-coupled battery inverters. What’s the difference? Read my post on the difference between AC and DC-coupled solar batteries. The Fronius Gen 24 is a true battery-ready inverter. Ready and waiting for a BYD battery.

Who is BYD?

Build Your Dreams. I’m not even joking. That’s what BYD stands for.

In 2019 I was over in BYD’s hometown of Shenzhen, which happens to be one of the world’s fastest-growing cities. Shenzhen is a city where many dreams have been built. You’d be forgiven for thinking BYD owns the bustling city of Shenzhen. The electric buses and taxies that rule the roads are all BYD vehicles. Billboards and buildings advertise the hope-filled acronym. Then there’s Mr Warren Buffet, the most successful investor of the 20th century. In 2008, Buffett made a big bet on BYD by taking a 24.6% stake in the battery and electric vehicle company. BYD is now the world’s largest manufacturer of electric vehicles.

BYD is an enormous company, has impressive experience with batteries, and has solid backing in Mr Buffet. Anecdotally they have been proactive with early Solar Battery warranty problems in Australia. But what about the BYD & Fronius combination?

Fronius and the BYD Solar Battery

In the ideal world, I’d have a Fronius battery with a Fronius inverter. If anything goes wrong, it’s clearly a Fronius problem. But Fronius decided to drop the Fronius battery and partner with BYD. Bugger. Now when there is a fault, who do we blame?

Crossbreeding solar batteries and inverters has been a problem in the solar-battery industry since day one. It was a problem carefully considered by Fronius. However, to make the battery more affordable, Fronius decided they wouldn’t white label a battery with the Fronius Brand. Instead, Fronius looked long and hard to collaborate with a reputable battery manufacturer. They chose BYD.

I’m not loving the crossbreeding. But I’m relatively confident that I won’t be in the middle of a finger-pointing war when warranty concerns rear their ugly head. Let’s look at the tech stuff and see whether it’s worth the risk.

BYD battery warranty

The BYD HV batteries have a 10-year warranty or a “through-put energy” warranty, whichever comes first. The through-put warranty doesn’t allow you to do a full cycle every single day for 10 years – instead, it’s about 82 per cent of that. After 10 years it will have about 60 per cent of its original storage capacity. That’s a fairly normal battery warranty, and the Terms & Conditions don’t seem too unrealistic.

BYD battery size options

You can’t just grab any Fronius Gen24 inverter and any BYD battery and expect it to work. Your excess solar power needs to be carefully considered. The below pairing guide shows how long it will take to charge your BYD battery at the maximum charge rate. Note the sharp charge/discharge rate reduction between a 10kWh battery and an 11kWh battery.

Fronius Gen 24 changeover time

The Fronius BYD solution works in a blackout. Don’t take that for granted if you look at cheaper battery options. But in a blackout, we need to automatically disconnect your home from the grid.  (You don’t want your battery to be powering all the homes in your neighbourhood. Nor do you want to fry the poor bloke who’s trying to fix the fallen power lines.)

Let’s compare Fronius with Sungrow. Sungrow has slightly different methods to ensure you don’t fry the linesman:

Sungrow has an inbuilt automatic switch (a contactor) to disconnect your home from the grid. This means your household backup circuits continually run through the Sungrow inverter. In a blackout, Sungrow’s internal contact opens to disconnect your backup circuits from the grid. As soon as it disconnects from the grid, the inverter will form its own grid (using your stored battery energy) and continue to operate. The changeover takes less than 20 milliseconds. That’s an unnoticeable power interruption for lights. However, that doesn’t mean you have an “uninterruptable power supply” or UPS for your home office. In our tests, the Sungrow 20ms changeover time is long enough to crash a computer.

Fronius relies on an external contractor to disconnect the home from the grid. The inverter needs to verify that the third-party contractor has safely operated. The Fronius spec sheet says that you’ll be without power for 90 seconds, but my tests show the changeover time only takes about 40 seconds. Are 40 seconds really that long to go without power? Keep in mind your computer will crash either way. Take your choice: batteryless backup (Fronius)- or a 20-millisecond changeover time (Sungrow).

Take your choice: Batteryless backup – or a 20 millisecond changeover time.

As for ease and cost of installation – if your inverter needs to be a long way from your switchboard- Fronius would be an easier and more cost-effective solution. If the inverter is right next to the switchboard – Sungow’s method would probably be easier, neater and cheaper.

Blackout mode

Just because you have a battery, it doesn’t mean it will work – or work well in a blackout. The Gen 24 inverter can:

• Use the battery power to keep the essential load running (assuming your electrician wired it this way)
• Continue re-charging the battery (while the sun is out)
• Run 3 phase loads (Symo inverter)

Charge the BYD Battery with any old inverter

If you have an old solar system on your roof (with any brand of solar inverter), it can be used to help charge the BYD battery. With the use of a Fronius smart meter, we can use the excess power from your old solar system to charge your new BYD battery via the Gen24 inverter. The old inverter won’t stay on in blackout mode.

You probably wouldn’t want to do this with an old 1.5kW, but if you had a quality 5kW system installed, then it can be used to assist in charging your BYD battery.

The Fronius Gen 24 Build Quality

It’s beautiful. It reminds me of an evolved Macdonald’s drive-through speaker box with a self-serve credit card facility. Minus the regrets.

Available Fronius Gen 24 Models

As of October 2020, we got our hands on the first Gen 24 “Symo” or three-phase inverters. They are available in 6kW, 8kW and 10kW inverters.

In the first half of 2021, the Fronius “Primo” will be available for single-phase homes. They’ll be available in 3kW, 3.6kW, 4kW, 4.6kW, 5kW, 6kW, 8kW and 10kW inverters.

The Fronius Gen24 cooling system

Fronius has always built solid inverters but the Fronius Gen 24 takes it to a new level. For longevity and efficiency, power electronics need to run cool. And because hybrid inverters do twice the work of a standard solar inverter, the cooling system needs to step it up a notch. Fronius’s obsession with cooling is displayed in front and centre of the Gen 24. It’s a big 15cm fan, and it moves slower and quieter and even more effectively than the Fronius Snap inverters. The grill on the front draws air in and across the massive heat sink.

Compare the new Sungrow SH5k-30 for example. Sungrow is no fan of fans. They have a little internal fan, but that’s it. Fronius is cool and clearly takes cooling, efficiency and longevity more seriously than any other inverter on the market.

Fronius Gen 24 Uptime Design

While on the one hand, Fronius focuses on reliability, they also design their inverters to make repair and replacement fast and effective. The Fronius Gen 24 heat sink chassis and printed circuit board are one component. In case of an inverter fault, there is no mucking around. The installer will turn up with a new chassis and replaces the entire internal of your inverter minus your saved production data. No waiting around for spare parts, no replacing one component just to find another component fails a few months later. The Fronius Gen 24 inverter is designed to maximise your solar uptime.

Built for Australian voltages

One thing that jumped out at me was the Gen 24 Primo only has 4 large electrolytic capacitors. Fewer electrolytic capacitors mean less chance of failure. How did Fronius achieve this? Part of the complete redesign included dropping the maximum input voltage down from 1000v to 600v. That works out perfectly for Australian residential DC voltage limitations, and it makes the inverter run more efficiently.

Built for bigger panels

Panels are getting bigger in both dimensions and power classes. Inverters are not keeping up. As panels get bigger, their operating current gets higher. Take, for example, the QCell 390W panel. It has an operating current of  11.25 amps. If we parallel QCells panels into one input, then we have a potential of 20.5 amps going into that input.

The Gen24 has a big 22 or 25-amp input limit on one of the inputs. You’ll have no design problems with that. However, the second input of the Gen24 can only handle 12.5 amps. This is on par or better than all other 10kW inverters that I looked at, but it would have been nice to have a 25 amp input in both trackers.

The image to the left shows an example of design limitations we face because of the lower input current. In some cases, we may need to install two smaller inverters if you want to make the best use of your roof space.

No Screen: Grandma Mode 2.0

The Fronius Gen 24 comes with 2 simple lights. If one light is solid green and the other is solid blue, then you’re all good – apparently. I’ve always banged on about what I call “Grandma mode” or the need for a screen on a solar inverter. You should be able to walk past your inverter and get a quick idea if it is producing as well as it should be.

I spoke with Fronius years ago about this when the Gen 24 was under development. They made a good point. If you are going to have a hybrid inverter with a battery connected to your home, you really need to take the responsibility of keeping your inverter connected to the internet. Grandma, if you want a solar battery, then get the internet and learn how to use it.

And Fronius has made it easier than ever for even Granma to keep her inverter connected to WiFi. Tap the WPS button on your modem, then tap the optical sensor on the front of your Fronius inverter twice. The left light will be solid blue when connected. Then jump onto the Fronius Solar.Web (app or webpage) and check out how your inverter is running.

Built for installers

A great product needs a great installer. Great installers take pride in their work and want minimal visible conduits and cables if at all possible. The Fronius Gen 24 has been designed with this in mind. We can now bring our cables in from behind the wall, depending of course on the type of wall we are installing on.

The Gen 24 is packaged as 3 easy-to-install parts, with fancy 1/4 turn screws. It comes with spring terminals to reduce the chance of a poor electrical connection. It’s the little things combined together that make for a happy tradie and a great solar install.

The Award-winning Fronius Gen24

It’s not surprising that the new Fronius Gen 24 has collected a swag full of international industry awards, including:

i) The 2020 Intersolar Award – the most prestigious award in the solar industry;

ii) The HTW Berlin University of Sciences awarded Fronius first place for efficiency with the Fronius GEN 24 Plus 10.0 inverter and BYD Battery-Box H11.5,

iii) The Plus X Awards recognised the Fronius Gen24 in four categories: High Quality, Ease of Use, Functionality and Ecology;

iv) The 2019 Red Dot Design Award.

Conclusion

The Fronius Gen24 was worth waiting for. PV point (or batteryless backup) means you are part way to being blackout-proof without the expense of a battery. Coupling with a BYD isn’t a perfect scenario, but I’d call it a safe bet working with two highly reputable and established companies. With a BYD battery connected, the Gen 24 will do everything you would expect (but often not get) from a hybrid inverter. But it’s the build quality of the Gen 24 that I’m focussed on. Its input current is not flexible enough for all roof layouts, but it’s great for most. Hybrid inverters by their nature cop a hiding because of the additional energy throughput. The Gen 24 build quality is displayed front and centre, and right down to the finer details. And given the Fronius Gen 24 swag of awards, I’m not the only one who thinks so.