SMA’s Sunny Boy: Under The Hood. Chinese vs German Manufacturing

chinese and german sma sunny boy

2 x 5kW SMA Sunny Boy Inverters. One made in China (SMA SB 5.0-1AV-40), one made in Germany (SB5000TL-21). How do they compare?

SMA have released a new single phase inverter. They kept the same joyful name of “Sunny Boy” however the model has changed from what was known as the “dash 21” to the “dash 40”.

But let me tell you a well-known secret about the SMA “dash 40”. The respected German manufacturer is manufacturing these new SMA inverters in China.


Has this turned the single phase model of SMA inverters into a cheap Chinese inverter? To find out, I bought myself a 5kW Chinese-built SMA “dash 40” and pulled it apart to compare it to the 5kW German made “dash 21”.

In this post, I’ll first look at the external features: the “smart screen”, the Sunny Home Manager, and the inbuilt DC isolator.

Then I’ll look at the internal build quality, and where the different components are manufactured. Finally, we’ll discuss the after sales service and warranty of SMA.

While writing this blog I had lengthy discussions with Scott Partlin from SMA. Scott is well respected in the solar industry. He was very candid and helped me understand the direction SMA are heading and the reasoning behind what SMA have done with the new Chinese Sunny Boy that, as they fairly put it, is “assembled in China”.

Part 1: The Externals


Where is the Sunny Boy screen?

The first thing that screams out when you look at the SMA is there is no screen. The display screen, I am told, was the most common failure point in the SMA, so the clever German engineers got rid of it.

Kein Problem! ”

The idea of leaving the screen off is not new. My friends at Sungrow pioneered the stupid idea with their new Crystal series. But thankfully Sungrow (because they are Sungrow) listened to the installer outrage and gave us an optional plugin screen.

Rather than marketing “no-screen” SMA have used the euphemism “Smart Screen”. Instead of a screen, we now have the ability to connect the inverter to a smartphone, and the inverter has three simple indicator lights to indicate the inverter’s status.

sma smart screen

Introducing the SMA smart screen. It’s on your smartphone. Geddit?

In my business, it is common to get calls from random homeowners who wouldn’t know the difference between an inverter and an instant gas hot water system. They want to know if the solar panels on their new home are working. In fairness, the majority of the time, if the “green light” is on, the solar is working reasonably (assuming they are in fact looking at the inverter). But I always spend a bit more time and ask the homeowner to give me a few readings from the inverter screen. I crunch some numbers to get a clearer picture of the systems’ performance.

Occasionally although the “green light” is on, there are system performance issues, so we arrange an onsite service. This type of “unplugged” diagnosis will be no longer available with the new SMA. The homeowner will have to be technical enough to work out how to connect their mobile phone to that Smart Screen inverter thingo – not to mention remembering the password!

I have no doubt that removing screens will increase the occurrence of some solar systems being left underperforming and undiagnosed. That’s not good for anyone.

On the other hand, there is no doubt “..a fault has come to light with the Comms interface where it seems to be unreachable and hence the inverter can’t commission/operate.”

All I want to know is: why do people use the word “hence” when the word “so” would have done just fine? Anyway, what’s so good about the Smart Screen?

Smart Screen vs. dumb screen

SMA obviously carefully considered going screen-less. Here are their reasons:

  1. Removing the inverter’s display screen will reduce manufacturing costs and reduce warranty issues.
  2. The “smart screen” will allow for much more information (historical data etc.) than the dumb screen.
  3. The smart screen can be updated automatically by SMA. In a rapidly developing industry, that’s nice!
  4. The smart screen will make way for what Scott called a “digital compliance paper”. In short, this is the world where an inverter becomes more about software than hardware. You make and ship a million identical inverters. If the customer wants a 2kW inverter, the installer unlocks a 2kW inverter. If they want a 5kW inverter, pay a bit more and unlock a 5. The inverters are all the same, but you pay for access rather than for hardware. In case you think SMA are dreaming, ABB and Huawei are planning the same.

Smart Screen and dumb screen?

Unfortunately, it seems that the industry is moving towards removing inverter screens to reduce production costs and warranty issues. ABB are considering dropping the screen in their next model. Thankfully SolarEdge’s brand new HD Wave currently has a screen, but they too are in early talks about dropping the screen in their next generation. My take? Until the concept of a “Smart Screen” is proven reliable and widely adopted by consumers we need an option of a basic plug-in screen similar to Sungrow’s. Plug-in screens will be more reliable as the exposure to the internal heat of the inverter will be removed.

Hey, solar inverter manufacturers – be like Sungrow.

SMA Energy Meter

Energy consumption monitoring was always possible with the old Sunny Boy. The problem was it was expensive and complicated. The new Sunny Boy SMA Energy Meter is now like the Fronius Smart meter. It simplifies the process with a kWh meter that connects directly to the inverter. Both the SMA and Fronius meters monitor:

  • how much grid electricity you use
  • how much solar you use
  • how much solar you feed to the grid.

They then graph this data on an online platform (SMA’s can also be accessed directly on the device without Internet). Both also allow zero export to the grid to be directly configured on the inverter.

Consumption monitoring has enormous benefits as I have previously explained. The difference between the Fronius and SMA’s monitoring is what the inverter can automate with that information, which brings me to SMA’s Sunny Home Manager.

Sunny Home Manager 2

The Sunny Home Manager 2.0 (SHM2) is an upgrade to the SMA energy meter. Not only does it monitor your power, but it can also and help you make the most of your solar energy. It will be available in June 2017. It combines all of the features of SMA’s old Home Manager and the Energy Meter into one device. The product includes weather forecasting to estimate the amount of spare solar energy 48 hours in advance. The Home Manager can then directly control “smart” devices through an Internet-connected cloud system to divert solar energy for consumption on site.

SMA’s choice to make load control funkier seems more complicated. The SHM2 can communicate via radio signals or EEBUS to fancy third party plugs that can connect to your washing machine or dishwasher. Alternatively, you can connect directly to a compatible appliance like a heat pump. Without being too dismissive, this level of home automation isn’t yet where it needs to be, especially because compatible appliances are not yet on the shelf in Australia, never mind in the customers’ home.

More importantly, SMA missed the low‐hanging fruit. The new Sunny Boy didn’t allow for a programmable “dry contact” to cost effectively control hot water with a simple relay. The Fronius solution simply uses the standard Fronius smart meter to automatically switch on your hot water tank on when excess solar power is available1. This method won’t heat 100 percent of your hot water with solar, but when correctly designed, it’s a cost‐effective and durable method of getting most of the way there.

I should explain I work in Brisbane’s market, and my bias towards simple hot water load control has a lot to do with Brisbane electricity tariffs and other local variables. Some of my customers – and many others around Australia – will see more value in more expensive hot water diversion. I explained the concept of hot water diversion in this post. Since I wrote that post, Fronius, SolarEdge, and CatchPower have all entered the market with similar devices.

Inbuilt DC isolator

The new SMA Sunny Boy comes with an inbuilt DC isolator. The advantages of having an Australian Standards compliant inbuilt DC isolator are:

  • The installation looks neater without extra cables, conduits and enclosures,
  • It ensures a high-quality DC isolator designed specifically for the inverters load, and
  • It ensures that the IP rating1 of the isolator is not dependent on the installer’s workmanship.

The problem with SMA’s inbuilt isolator: it’s not yet compliant.

According to the relevant Australian Standards, to comply installers must provide one of the following:

  1. (a)  An adjacent and physically separate switch-disconnector.
  2. (b)  A switch-disconnector that is mechanically interlocked with a replaceable module of the PCE, and allows the module to be removed from the section containing the switch-disconnector without risk of electrical hazards.

(AS 5033 clause

English Translation: to be compliant, the DC isolator must be capable of remaining behind on the wall if the inverter needs to be replaced under warranty. So if we install a Sunny Boy inverter, we also have to install a separate third party DC isolator adjacent to the inverter.

There is a push by SMA and others in the industry to have this clause amended, and rumour suggests this may happen in the next 12 months. The standards update would make Sunny Boy’s DC isolator compliant. However, while SMA has the support of the Clean Energy Council on this proposed amendment, CEC tech support advised me:

“Don’t hold your breath.”

Fronius had been the only inverter that has a compliant inbuild DC isolator, but the SolarEdge HD wave has just matched it. With Fronius and SolarEdge, this allows for a cheaper, simpler, neater installation and requires no additional third party isolator for warranty purposes.

Part 2: The Internals

The electronics

The question remains as to whether moving to China will impact the quality of SMA inverters. Let’s have a look under the hood.

German SMA internal

The old German SMA has one large printed circuit board. Everything about it looks immaculate – as you would expect from SMA.

Chinese SMA internal

The Chinese SMA is made up of four separate boards:

  1. The Control board is still made in Germany and is shipped to the Chinese production line. This is the board that sets the limitations of the inverter, the grid codes, and interfaces with the grid.
  2. The communication board is also still made in Germany. The name says it all. It’s responsible for WiFi and EEbus connectivity.

    There is irony here: the part of the inverter that has been failing in the Chinese SMA was the Communication board – the part that was made in Germany!

  3. The power board is made in China, not at the Chinese SMA factory, but at another third party PCB manufacturer. This is where the DC to AC conversion happens. It’s what replaced the transformer in old inverters to make inverters transformerless. The board uses H5 Bridge (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.
  4. The AC filtering board is also made in China. This board cleans up the AC wave that comes out of the Powerboard for compliance.

Zoom in

At closer inspection, the boards that were made in Germany looked neat. The boards that were outsourced to a Chinese PCB manufacturer were visually lacking. Take the build of the Chinese inductor on the AC filtering board for example. The inductor is made with a rough cut aluminium separator, sloppily wound tape make up the insulation between coils, and a blob of black goo to hold it all together. The German made inductor looks like… Well, it looks like it was made in Germany.

German SMA inductor


Chinese SMA inductor

Stainless Vs. Zinc

Another example is the various fasteners inside the inverter. The German stainless steel torque fasteners are designed for overkill with machine torqued tightness and stainless longevity. The Chinese Phillips head zinc plated fasteners were designed to save money. Add a healthy blob of silicone on that plug for good measure. Maybe I’m nit-picking – but no more than they were in the German factory. The aim of the SMA-40 was always to cut costs and stay competitive in a competitive market. Cutting costs has resulted in a compromise of craftsmanship. Time will tell if that translates into reduced reliability.

German torque stainless bolts


Chinese Phillips zinc bolts

 Fewer Capacitors


Capacitors (found on the power board) are a key component to string inverters. Decreasing the number of capacitors will decrease the cost of the inverter. The new SMA has cut costs by installing only eight capacitors. Compare this to the previous SMA which has 10, and the Fronius which has 12. A key reason you need more capacitors is to increase the inverter’s DC voltage limit. The new SMA can have a Maximum of 600 volts; the old SMA could take 750 volts, where the Fronius can cop a massive 1000 volts DC.

So a higher voltage is better right? Well, not in a domestic situation where we can only have a maximum of 600 volts DC anyway. As it turns out, less is more! For best efficiency, we want to match the inverter’s nominal DC voltage closely to the voltage from the panels on the roof. This tends to be below 500v in a home.

This is one place where the SMA trumps the Fronius. (However, Fronius are coming with a new model in 2018, and a little birdie told me they would fix that capacitor/high nominal voltage issue.)

No Fan

SMA heatsink (removed from the back of the inverter case)

The new Chinese SMA is fanless. It uses a large heatsink to keep the inverter cool.

The upside to not having a fan is less moving parts to fail and less noise.
The downside is the ability to move heat away from the electronics.

The previous, almost indestructible German Sunny Boy was also fanless, so I’ll resist suggesting an internal fan would be better.

Part 3: Support and Warranty

SMA support

SMA technical support over the last 12 months has been, at times, pathetic and they openly admit it. When I asked Scott why, he explained that Germany enforced a “head count freeze” last year, so SMA Australia was understaffed. They also had notorious phone systems issues.

But with the introduction of the new Sunnyboy, SMA Australia are well and truly back on the horse. An installer recently told me that although he had 2 SMA-40’s “dead on arrival” he couldn’t fault SMA’s after sales service in this instance. That’s a promising sign, at least for their support team.


Their new SMA warranty procedure also sounds promising. If an SMA inverter is connected to the internet and registered with SMA, then SMA will be notified automatically of any inverter errors. SMA will then proactively arrange an inverter replacement with the installer with a guaranteed five-day delivery. (This is a far cry from the painful procedure we had to go through with the very occasional SMA-21 inverter we had to claim under warranty.) Even better, because the cost of manufacturing SMA inverters has dropped so low, all inverters that fail within the warranty period will be replaced with a new inverter rather than be repaired.

SMA currently offer a 5-year standard warranty. It’s $325 to add a basic 10-year warranty. SMA are considering making a 10-year warranty standard. Let’s consider the following premises:

  1. SMA are up against a SolarEdge 12-year warranty and a Fronius 5+5 year warranty.
  2. SMA has always been a reliable inverter, with a failure rate of less than 1 percent.
  3. The screen was the weak point in the SMA-21, and they removed it in the new Chinese model.
  4. Building the inverter in China will not reduce reliability.

The conclusion: The decision to offer a 10-year warranty would be a no-brainer. Unless, of course, premise 4 is incorrect.

For me, this is the clincher. Will the build of the SMA-40 be as reliable as the good-ol’ German SMA-21? SMA would know the answer to that question best. Let’s see if they put their money where their mouth is, and offer a 10-year standard warranty.


The new Chinese SMA Sunny Boy inverter has unashamedly cut costs. They dropped the screen on the front of the inverter, and it seems the industry is just going to have to get used to that.

The SMA energy meter is a welcome addition: load monitoring should really come standard with solar systems today. However, the load control that SMA offer with their Sunny Home Manager 2, is a little too advanced to be of much use today.

The DC isolator is not yet compliant, but if the relevant standards are amended, it will make for a neater, safer and more cost-effective install.

The printed circuit boards made by a third party in China look a little sloppy, but ironically it was one of the German made PCB’s that failed in the rollout of the new Sunnyboy.

While the after sales support is looking promising, the SMA warranty period needs to be extended. It will be interesting to see if SMA back their Chinese made product with a 10-year standard warranty.


  1. IP rating determines whether water will get in to an enclosure and go bang!, as up to 600V DC short circuits
About Mark Cavanagh

Mark is the owner and manager of Brisbane based solar installation company MC Electrical. He is an electrician and an accredited solar installer with over 20 years’ experience.


  1. Stewart says:

    Thanks for the interesting article Mark.

    I recently had a solar system installed and it came with the new SMA inverter with no display. I can understand for a layperson the display is probably easier to access information especially if the owner is non tech-savvy.

    There are a number of ways to get the information out of these boxes and you don’t have to use a smart phone. My install I had an Ethernet cable installed and connected it back into my router as I prefer using Ethernet around the house where my devices have Ethernet sockets. The Inverter should by default be using DHCP and be assigned a LAN IP address by the router. Normally the router will just assign the first free unused LAN IP address. I use the Inverter’s Ethernet MAC address and tie it to a specific IP setting in the router so I know exactly what IP address it has. They are still served as DHCP connections as far as the Inverter is concerned.

    To access the SMA box I just use (for example): http://192.168.1.x in a web browser on a PC.

    The above should also be possible by having WiFi connect to the router but requires the SSID and WiFi password to be configured in the Inverter. That’s probably going to create headaches for the installer though if the owner changes their WiFi log-in credentials!

    Thirdly just use the built in WiFi acting as an Access point. It’s basically a WiFi DHCP router like an ordinary router has. I believe this is what the installers use to configure the boxes. The log-in details are on the back of the supplied manual on a sticker.

    I don’t like leaving the WiFi Access point switched on as it is a security issue (broadcasts the SSID) so I disable that side of it and only enable it if needed by the Installers so they can access the Inverter while on site.

    Lastly it should be possible to configure the router to open up a port in the router to the Inverter so that the Installers can configure it from any place in the world. You need to make sure the passwords are secure though (don’t use default ones). Problem with this is that it can be a pain to configure in the router especially for a non tech-savvy owner but might be worth doing if installer is not located close by and needs to fine tune the Inverter frequently.

    I don’t think the low level settings in the box can be configured via the SMA SUNNY PORTEL site? If that was possible it would make life easier for Installers.

    Just a quick note on the Chinese Inductors. The yellow tape looks like standard Mylar Inductor tape designed for the purpose. Where I once worked we used to custom order 100s of these from Chinese manufacturers for use in Inverters. Very cost effective and reliable. They used the same sort of core re-enforcement. There are probably 1000s of small businesses that produce these in China and they are very competitive.

  2. don firth says:

    I removed the booster capability on my heat pump when I installed it and also fitted a time switch so that it only comes on at midday when air temperature is most efficient and solar panels are most productive ( on average) so it’ sefficiency is maximised- thus not needing smart technology to optimise.

  3. I hardly ever used the display as the inverter is in a corner of my garage.
    I just find the Oxley Solar display app on my phone more useful .
    Add the SMA ethernet connection back to base and what more do I need?
    I would have liked a monitor because I have to use 2 monitors one from Owl and the other from Engage as I have 3 phase power and I just have not got enough connectors to monitor my power at any given moment accurately.
    The AGL app gives me a daily consumption but its two days out of date and I am not actually sure what it is measureing , I assume it measures total consumption and then some how works out the cost per meter .

    • Hi, Eric, an ethernet connection is definitely the most stable. I hadn’t heard of the Oxley solar app. I just looked it up – looks good! Sounds like you are all over it! I’ve just moved into a new home and we are going with AGL, partly because I want to check out and review their monitoring platform 😉

  4. Erik Christiansen says:

    Very informative article!

    The core-insulating tape on the Chinese inductors looks OK, but why on earth use an aluminium winding separator? Such a common-mode choke has line voltage between the two windings (hence the insulating tape) and any physical separator should very definitely be non-conducting. The enamel on the wire is sufficient for inter-turn insulation, but nothing more. And the oxide layer on the aluminium offers no useful insulation at all. Much better would be a bead of non-melting goop in each inter-winding gap, and NO aluminium.

    Yes, there is a physical barrier across the diameter of some of the 240v common-mode chokes I have within arm’s reach _but_ they are made of plastic. They fit into slots in the plastic insulating jacket moulded onto the toroidal core, so they can be installed after coil winding.

    I’d be curious to hear which test house performed compliance testing on the dash-40, as it should not have passed with that metal short-circuit risk, in my opinion. All it takes is for either end of both windings to contact the metal, then electrical breakdown would be immediate, I suggest.

    I’d definitely make sure my fire insurance was fully paid up before installing anything with a chunk of aluminium which could short out the input or output power bus.

    Substitution of large heatsink fins for a fan sounds very good, though. After the display, the fan would be the first thing to give up, as in other equipment.

    Get rid of the aluminium on the choke, and I’d consider one.

  5. Great article Mark. Thank you very much.

    In the TL20000 EE, SMA has left out the screen as well. In my experience the screen is quite vulnerable, especially if the inverter is mounted outdoors.

    The fan is indeed usually one of the most common failure points as well. As long as the passive cooling capacity is sufficient, I think it is a good move to leave the fan out. Fans usually need to be cleaned and checked on a regular basis. These 5KW inverters are obviously used in the residential systems, which are know particularly know for their intensive O&M cycle. A truck roll is relatively expensive if you look at the number of kWh’s that you gain in a residential system.

  6. From Facebook: Zeversolar 5kW vs. SMA 5kW

    • Erik Christiansen says:

      Finn, are those really aluminium separators across the common mode line chokes? If they are, have you asked whether the design has been subjected to compliance testing? Plastic would be fine, but a gooped-in-place conductor only has to become loose enough to touch both coils, and you have a line short. Not only does electronic equipment stop working once the magic smoke is let out, but at 5 kw there’ll be more than just smoke.

      When returning a busted Chinese compressor, the response has been “Put it against the wall with the others, and take a new one.” If that’s to be the approach with their inverters,I’d hate to have just inverter s/c detection between me and a house fire. We need to demand adequate construction.

  7. Conan the Grammarian says:

    “I was at home working on my Sunny Boy inverter, so I couldn’t be at work to take your call”

    The word “so” has two subtly different meanings, depending on the context – was the speaker above explaining his absence, or confessing to having concocted a way to avoid speaking to the listener?

    “I was at home working on my Sunny Boy inverter, hence I couldn’t be at work to take your call”

    Much clearer – turns out he wasn’t being a jerk to the listener after all.

    You asked.

  8. don firth says:

    In the original quote the comma after the word inverter implies two separate thoughts, hence the first explanation is the only actual meaning, but we digress…..

  9. Praashekh says:

    I just got the SMA Sunnyboy 5.0-1av40 fitted at my house but the wifi connection wasnt set up perfectly i guess. I can see the solar energy produced by the device but the box that shows the energy consumption has no reading, Neither does the energy feed-in management section. (this is when i log in through the i.p address link). On the sunnyportal these options aren’t there at all so i’m quite unsure if the SunnyBoy 5.0 is even capable of telling me the energy consumption of my house or if its just a case where the install was not perfect.
    Any advice would be helpful. Thank you.

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