Sunsynk 5 kW (5.5-K-SG01LP1) Hybrid Inverter - Technical Review

Note: Since this is a review of a residential-type inverter, the context of this article is with the energy requirements of a residential solar/energy installation in mind.

Welcome To Load Shedding

The Sunsynk hybrid inverter was a small revelation when it began to gain prominence in the South African solar energy market circa 2019/2020. 

South Africa was in the midst of a growing energy crisis that had begun in 2008. The government-owned energy parastatal, Eskom, was increasingly unable to meet energy demand, resulting in daily energy cuts euphemistically termed "load shedding" that operated on a graduated "stage"  schedule depending on the severity of the energy generation shortage. The greater the energy shortage, the higher the stage and more frequent the number of daily power cuts that lasted between two to four hours at a time.

The growing energy generation crisis, shown in total number of hours of energy cuts. 

Naturally, businesses and residents that could afford to do so began seeking alternative energy solutions. Many early adopters initially turned to petrol and diesel generators as they were readily available in various capacities and generally ubiquitous, whereas solar generation and especially battery storage was considered expensive and more niche, despite South Africa being generally well suited for solar generation due to its high average solar irradiance (220W/m²). Part of the immediate challenge with adopting a solar solution was providing a complete alternative energy source that could bridge the whole or part of the load at all times and not just supplement it for energy cost reduction. This would require the inclusion of battery storage in all solutions, generally unheard of in other more developed solar power markets. Before approximately 2018, this may have conjured images of large banks of lead-acid batteries, which required a fair amount of space and a degree of technical pampering that probably put off most consumers.

This view of solar generation gradually began to change due to a number of factors:

• The global cost of solar panels declined continuously over the energy crises period.
• The advent of lithium-chemistry batteries in commercial and residential applications became more readily available, and despite the higher upfront cost, the return on investment case of these batteries began to make economic sense vs lead acid. They were also generally more consumer friendly and more compact with different mounting options becoming available later.
• As the energy crisis deepened, generator running costs started to become prohibitive.

Rise To Prominence

Around 2019, the types of power inverters on the market included a cohort of lower-cost off-grid inverters, dominated mainly by Voltronic designs, and these were and are still quite prevalent for "UPS" type applications, although they are officially not permitted to be connected directly to the generation grid - but they often are anyway. They of course have other issues, especially related to longevity and their inability to feed solar power to the grid-side connection. In the South African context, this was useful to extract the maximum benefit from the investment in solar panels to feed non-essential grid-side loads such as pool pumps, stoves and hot water heaters (geysers), rather than, paradoxically, feed energy into the grid. Thus, grid-compliant hybrid-type inverters started to become more important and at the time, there were a handful of available options, two of the most prominent being Victron and Goodwe. 

Victron makes excellent equipment that can be configured to your heart's desire but is an expensive option for the local market, and most installers did not understand where to begin to build and operate an inverter/solar system based on all the various discrete components required. 

Goodwe is a Chinese manufacturer that offered a small selection of hybrid inverters for residential applications that provided an "all-in-one" solution that most installers could understand. Bolt the box to the wall, make all the necessary electrical integrations and connections, connect one or more batteries and optionally add some solar, and you had a complete power backup solution. These, especially the 4.6 kW 5048D-ES model, appeared to sell fairly well, but had a few shortcomings. While the hardware quality seemed good, the software, as the inverter's firmware and thus configurability as well as the phone Apps that were used as the user interface, was relatively basic while also being rather buggy. This model also had issues with it's WiFi connection that often stopped working for no apparent reason.

The Goodwe 5048D-ES was a popular, passively cooled design

Sunsynk, a UK company, began to become noticable on the local market in late 2019. Their inverters are based on designs from a Chinese OEM manufacturer, Deye. Both brands have hardware-identical models, but the Sunsynk models change the style and layout of the inverter's touchscreen user interface (UI) - settings and functionality are otherwise the same. A +-5 kW inverter capacity is often a good entry level capacity for offsetting the effects of load shedding on a typical local household. This includes operating most if not all lights and plug circuits in the home, but excludes non-essential loads such as the stove/oven, pool pumps, air conditioners and hot water heating. Thus, when the Sunsynk (and somewhat less so, the Deye) 5 kW hybrid was launched, it rapidly supplanted the Goodwe and any other brands as the hybrid inverter of choice. It is an integrated hybrid inverter, like the Goodwe, which makes it easy to install and understand. It was also economically priced and cheaper than the Goodwe inverter which made it instantly attractive, but also boasted a better feature set, the most relevant of which we will unpack further.

A Play On Words

The Sunsynk is a true hybrid inverter. Unfortunately, there appears to be a growing trend in use of the word "hybrid" with cheaper, off-grid inverters to denote an inverter's ability to "blend" power sources in order to supply the load, which is rather misleading.

Here, when I refer to a term "hybrid", I'm referring to the ability of an inverter to supply power on both the backup connection as well as the grid connection. The latter ability is synonymous with being able to feed power back into the grid, but it is also used, in conjunction with a feedback control mechanism, typically a current transformer (CT) coil or power meter, to supply power to loads connected on the grid connection side of the inverter. These are the non-essential loads, in that they will not operate if the grid is off. A hybrid inverter can supplement power to these non-essential loads from solar or battery power, as long as the grid is operational. This constraint is present for safety reasons, as we do not want inverters to supply power to the grid in case the grid has been shut off for maintenance reasons for example. However, when the grid is operating and the inverter has an excess of solar energy available, it could feed that energy to a pool pump or hot water heater for example and maintain zero grid feed-in due to the CT. Alternatively, it could allow the feed of that excess energy to the grid if that is permitted by the grid authority and makes economic sense to do so.

Possible energy flow with a hybrid inverter. Note the CT coil/power meter is connected to the inverter and is used to measure the power flow between the grid and the inverter so that the inverter can regulate if any power flows back to the grid or not. Most importantly, the inverter cannot feed power on the grid side (orange) if the grid is not operational.

When used with solar panels, a hybrid inverter is generally preferable over an off-grid inverter, not only because the off-grid inverters are typically not certified for grid connection, but also because the hybrid's ability, at minimum, to allow feeding excess energy to the non-essential loads as well. This makes it better at realising the return on investment in solar panels by increasing the panel utilisation. However, hybrid inverters tend to be more expensive than off-grid inverters, but carry longer warranties. In my experience, the notion that "you get what you pay for" usually applies.

Sunsynk Box Of Tricks

The Sunsynk 5 kW inverter is moderately sized, conspicuously rectangular in shape, with a large passive heatsink on the rear, and a touch screen display on the front.

Inverter specifications on the PV side are modest

The inverter can generate a maximum of 6.5 kW of solar power from up to two suitably sized arrays. The MPPT voltage ranges and current ratings are a bit underwhelming. The MPPT starting operating voltage of 150V means at least four 400W type panels connected in series will likely be required per string. The maximum voltage limit of 500V results in around nine 400W panels on a string being the usable maximum. While not bad, other designs are available that have wider PV voltage ranges, allowing for lower minimum and/or higher maximum panels counts per string. For example, the Goodwe 5048ES model the Sunsynk supplanted had a maximum voltage of 580V per string.

Of greater vexation is the string current limit of 13A, which has actually increased slightly over time. On early versions of the inverter, this was pegged at 11A, barely sufficient for some 400W panels, but this was increased through firmware updates. The 13A limit means use of many contemporary panel sizes above approximately 540 W are less economic as the inverter will simply limit the maximum string current to 13A, thereby limiting the overall string power even if the panels can supply more. Given the trend to  higher wattage panels, the Sunsynk's PV design specifications could do with an update.

On the plus side, the inverter has both Type II AC and DC surge protection integrated, although it would be useful to know the breakdown voltage of the protectors if additional external protection is to be installed.

Although IP65 rated, the inverter should not be mounted in unprotected areas, with exposure to rain or direct sunlight for example. Additionally, in South Africa, mounting the inverter in an exposed location would likely also result in waking up one morning to an empty space on the wall where your expensive inverter was once mounted.

Installation

The inverter itself is straight forward to install, especially due to the inclusion of a separate wall bracket. Once the suitable location has been identified, the bracket can be mounted to the wall and then the inverter can easily be hung and secured on the bracket. It is unfortunate that Deye is not consistent with their use of such a bracket across all models as evident on other single phase models (8 kW, 10kW, 12kW) which have only chassis bolt tabs, requiring a fair degree of gymnastics and people power to hold the heavy inverter while it is being mounted.

The inverter's mounting bracket is easy to install and holds the inverter securely.

At the bottom side of the inverter, two pairs of PV inputs are provided as MC4 connectors, one pair per MPPT. Various glands provide entry points for any cabling required, although these are often unscrewed and replaced with 20 or 25mm glands that will accept flexible cable sprag for a neater (and potentially electrically compliant) installation. A DC isolator switch for the PV circuits, a power switch and RS232 port for the WiFI dongle round out the items of interest here. A centrally mounted touch screen (approximately 75 x 50mm) and four membrane-type buttons are mounted on the front face of the inverter.

Inverter bottom face with all connections, switches and Wi-Fi dongle rear-right.

Internally, screw terminals for AC grid, and backup and auxiliary connections are provided, the latter's function being configurable as either an additional load output or generator/micro inverter input. 

Two relatively small M6-sized bolts are provided for the battery cable terminals - it is critical these are tightened correctly as any DC arcing on these terminals will heat up the cable and potentially cause the battery cable insulation to melt or worse.

RJ45 jacks for pass-through parallel inverter connections, battery CAN BMS, DRM and an RS485 port for MODBUS connection for an external power meter to replace the CT if the distance to the grid input is very large, or alternatively for data exchange and potentially setting modification and control via third party devices/software. It should be noted that due to the surface mounted RJ45 jacks used, care should be taken not to insert a cabled connector into the jack and then place that cable under tension as this can result in the entire connector being pulled off the circuit board, and a very unhappy moment.

Removing the front cover with the supplied hex bolt key reveals the well laid out and labelled connections.

A push-in cable terminal provides connections for a lead-acid battery temperature sensor (which hopefully you will not use), the grid-side CT coil (white CT cable on pin 3 with the CT installed on the live grid supply cable with the arrow in the direction of normal power flow), a normally open generator start dry contact and a 240V AC signal that activates on grid failure. This is typically used for an external neutral-earth bond where required for electrical compliance as this bond does not occur automatically inside the inverter. It should be noted that if using the "Island mode" signal to activate the 240V AC signal, the GS pins are used as the generator start dry contact, otherwise the GV pins are used.

Cooling and Noise

Being a mostly passive design, the 5 kW Sunsynk should be unobtrusive in terms of noise. This however, has a few caveats. By design, the inverter has no external air vents to draw air into the inverter body, although early models did. A single internal, variable speed fan exists, that is evidently used for localised/spot cooling only when the inverter's temperature rises above a certain point. This fan can be nearly inaudible or loud enough to cause a notable hum, largely depending on how hot the inverter is, and what appears to be manufacturing variability. Concerns as to the effectiveness of the cooling are brought to bear as internal temperatures, as reported by the two internal temperature probes, can routinely go north of 80 degrees Celsius. 

The inverter can double as a space heater.

This can be corroborated by touching the inverter heatsink, which can become a decidedly unpleasant experience. This also leads to one wondering as to the longevity of the inverter's electronics, particularly capacitors, even although Sunsynk/Deye issue the product with a 5 year warranty. 

For one's own peace of mind, I would suggest mounting one or two 12cm fans at the top of the inverter that draw air up through the heatsink, ideally with a simple temperature controller who's temperature probe is attached to the inverter heatsink. The probe can be crimped into a suitably sized lug and screwed onto the side of the heatsink, or by using aluminium tape, which also works well. Once such cooling is in place, the inverter runs much cooler, but will of course be noisier, depending on the type of fans used.

Example of supplemental cooling using two 12cm AC fans controlled using a Sonoff TH10 Temperature Sensor/Switch. Temperature probe can be seen on the left adhered to the heatsink with aluminium tape.

Parallel Operation

A useful, although not unique, feature of the inverter is the ability to expand your system's capacity simply by adding more inverters - up to 16 in a single phase installation. or 15 in a 3 phase setup. There are some critically important requirements for paralleling inverters that are beyond the scope of this review, but are well documented in the installation manual.

Single phase parallel setups can work well as long as the firmware of the inverters is the same and all the installation requirements are adhered to. This setup has some advantages:

• Redundancy - should one inverter malfunction, it is possible to continue operating, albeit at reduced capacity while the non-functional inverter is repaired or replaced.
• More MPPTs - in a dual 5 kW setup, you would have 4 MPPTs, which if you have lots of smaller roof spaces in different directions, could be useful.

The downsides are some additional complexity but mainly cost, as additional switchgear, cabling, battery fuses and  battery busbars will be required for the common battery storage shared by the inverters.

In my experience, the use of multiple single phase inverters to create a parallel three phase setup can be tricky and often have issues (some being the "letting the smoke out" variety) and are best avoided. 

Configuration

An appreciable benefit of the Sunsynk is the immediacy of information that can be obtained and configurability possible once powered up, via the integrated touch screen.  The LCD display allows for direct configuration of the inverter without the need for a phone App. In addition, the interface used on the display is largely standardised across all the Sunsynk inverters, making configuration for installers simpler. Generally, there is a confidence that once you click on an OK button on the screen, any changes are applied, although sometimes not instantly. However, the user interface does also have some quirks in operation that is not always immediately apparent. 

The home page view provides a nice summary view of the inverter's current operation. You can also select the dials/gauges on the right hand side to get more detailed voltage and power information, or access the nice system power flow page which shows power flow in the system by selecting the bar chart.

The Sunsynk's home screen has real-time power dials on the right and cumulative data in bar-chart format on the left.

The initial startup of the inverter involves running off the lithium battery only, with no AC or solar connected until the correct battery settings are configured. The battery settings are accessed by clicking on the gear in the top right of the home page. 

Battery configuration starts on this tab. Note, the Activate function is used  specifically to slow-charge/recover a fully discharged battery and is not required under normal operation.

Generally, one would start on the Battery Type tab by setting the battery type to AGM V which allows for manually setting of the battery voltage ranges according to the battery used (on the Batt Charge tab), even if using a lithium battery. This is to avoid damaging the battery in case this setting is ever changed inadvertently or needs to be changed temporarily. Thereafter, switching to the Lithium mode allows the inverter to control the attached battery via the BMS cable connection, which is the preferred approach for a Lithium battery in order to get accurate state of charge values, and maximum charge and discharge currents and voltage setpoints.

The inverter implements the ubiquitous Pylontech CAN/RS485 battery protocols and thus, many lithium batteries are supported out of the box, requiring only that the BMS cable is connected, the cable pin connections are correct and the required interface type (CAN or RS485) is selected.

The overall allowed battery charge and discharge Amps (from grid and/or solar) can be set on this page and should not exceed the manufacturer settings. The battery capacity setting doesn't appear to be used for any obvious purpose.

Generator battery charge and settings in red on the left, grid battery charge limit and settings on the right.

On the Batt Charge tab, it is possible to adjust the battery charge and also voltage settings, if the battery type is set to AGM V on the Batt Type tab. Although not obvious,  the Generator and Grid settings are arranged in two columns, thus the Amps setting on the top left allows for setting the maximum Generator battery charging current, and the Amps setting on the top right defines maximum Grid charge current.

The Shut Down tab primarily allows for modification of battery SoC threshold values plus a few other settings that evidently could not find a home elsewhere.

Important battery SoC levels are configured on the Shut Down tab, with the Shut Down SoC percentage (or voltage, if the battery is operating in AGM V mode) defining when the inverter will disconnect all loads. Note, in this state, the inverter will continue to draw power from the battery to power itself until the battery shuts itself down, which may require manual intervention, such as a power cycle, to make it visible to the inverter again once a charging source (grid/solar) becomes available. If however, the battery does not shut down, the inverter will automatically begin charging the battery until it's SoC reaches the defined Restart value, at which point it will restore power to the backup loads. Therefore, normally, one wants to set the Restart value to maybe 5-10% higher than the Shutdown value to provide a charge buffer in case a cloud blocks the solar generation source for a few minutes, or to take into account the load may exceed the solar generation capacity for example, but not that high that it takes extended periods of time for power to be restored.

The next notable configuration section can be found under the System Mode icon in the settings. This consists of two tabs, creatively named System 1 and System 2. System 2 contains settings that adjust power limits, export and load/battery priority behaviour, but they are confusingly arranged. 

The System 2 configuration screen could do with some improvements

Notably, if you select Zero Export, no power will be exported to the grid if the CT is installed correctly, but if you select Solar Export, solar power will be exported to the grid, even although that check box is displayed as a sub-setting of zero export in the user interface!  So it's best to think of these are distinct settings, regardless of how they are presented. The Limit to Load only setting is usually left unchecked for solar installations and left checked where no solar is present, otherwise battery power will be used to power non-essential loads when grid is present.

Probably one of the defining features of all Sunsynk inverters can be found on the System 1 tab - the System Mode timer.

The timer allows for varying minimum battery SoC values and charging sources

This allows for up to six time slots to be defined per day, where most importantly, the minimum battery SoC can be defined as well as the energy/charging source if the battery is below that SoC, either Grid or Generator. 

Thus, if the minimum SoC is set to 50% between 03:00 and 05:00, if the battery SoC is actually 75% at 03:00, the inverter will continue to discharge power from the battery. If it reaches 50% within the time range, the inverter will switch to supplying the loads from the grid, if that option is selected, or a generator if that option is selected (or grid first if both are selected). If the actual battery SoC is 40% at 03:00, the inverter will use the selected source to power the loads, but also to charge the battery to the specified minimum SoC, in this case, 50%. 

This provides a simple but very useful way of varying the amount of energy stored in the battery to be modulated throughout the day, in order to take advantage of daytime solar generation, time-of-use tariffs, or to maximise solar energy storage, peak feed in tariffs and night-time usage of stored energy based on your own energy usage patterns and needs. Most other hybrid inverters provide a schedule based on time ranges that specify when to charge or discharge the battery and single minimum SoC value for all times, but the Sunsynk scheduler allows the same thing to be achieved in a manner that is arguably easier for most users to understand by focusing not on charging/discharging, but on what the minimum battery SoC should be at various times of day.

This was certainly borne out in South Africa, where increases in the "load-shedding" Stage due to unforeseen loss of generation capacity could mean periods of grid availability could vary day to day or change at relatively short notice. In such cases, most user's only concern is how full their batteries are, especially heading into the evening peak or overnight. The ability of the Sunsynk App to allow these values to be modified remotely at any time using the App, at minimum by the installer but often also the end user, was another reason that continues to contribute to the inverter's popularity.

The Aux Load page, as with other pages, contains some undocumented and unclearly documented functions. The Gen Load OFF Batt setting is also fixed and cannot be changed - in most cases, this is irrelevant as using the System Mode Timer overrides the battery generator OFF SoC value.

Other general settings pages for basic (date/time, access control), grid, and other "advanced" options are available, the latter including controls for the Auxilliary input port behaviour which can be defined as a generator/micro inverter input or auxiliary/smart load output. The generator input option is probably the most common way of using the AUX port, where in case of extended grid outage, a petrol or diesel generator can be used to provide power to the loads and ideally, also charge the batteries. For larger generator installations, it is usually more efficient for the generator to run at a medium to high load for a shorter period of time, say 1-2 hours, charging the batteries, before shutting off again. This also avoids various mechanical implications for the generator by consistently running at light load.

It should be noted that the minimum recommended generator size for the most-fuss free integration would be twice the inverter's power rating, so an approximately 10 kW generator should be connected to a 5 kW inverter. This is because the inverter switches the entire backup and battery charging load, less the difference provided by any solar power onto the generator when the generator is running, and thus the sum of both of these loads needs to be considered. Smaller generators can be used but will require more careful, and thus manual load management when used, otherwise the inverter may end up in a cycle of constantly connecting and then disconnecting the generator due to its output frequency dropping below acceptable limits when the inverter switches over the potentially high load.

Also noteworthy is that when connecting a generator to paralleled inverters, the generator input must be connected to all inverter AUX ports, otherwise the parallel inverters will not accept/switch to the generator input. This is point of confusion for many given the contrary information previous provided by Sunsynk themselves in this regard.

The AUX load output can be used to connect "nice-to-have" loads to the inverter that can be controlled according to the presence of grid, or battery SoC levels. That is, if grid is present, the output can be set to always operate, or operate only if the battery is between 100 and 60% SoC for example. Note however, that the AUX port forms part of the inverter's total output power budget, so if the grid is not available, a maximum of 5 kW is shared between both the backup and auxiliary port.

Finally, a micro or grid-tied inverter with a maximum capacity of 4 kW can be AC-coupled on the auxillary port as an additional power input as well. The Sunsynk inverter can use a configurable frequency shift to control the attached inverter's output power. However, the behaviour of the inverter under this setting is not clear in terms of if it will switch the entire load/battery charging on to the micro/grid-tied inverter as per the generator arrangement or if the input will just serve as an additional, combinable AC source.

Sunsynk Connect App

Early versions of the Sunsynk inverters, like Deye versions, used the Solarman monitoring platform, which was...ok. However, it is a bit convoluted to use and remote control of inverter settings, while apparently possible, is not simple or obvious to achieve,

Evidently realising this, Sunsynk moved to their own platform called Sunsynk Connect. It is possible to change an inverter currently using the Solarman platform to the new platform by purchasing a new Sunsynk wireless dongle and replacing the Solarman dongle connected to the inverter. This is worth the money as the new platform is better in almost every way and there is no additional cost associated with it's use.

After following the instructions to pair the WiFi dongle with your WiFi network that provides Internet access, you can create an account on the Sunsynk App and then add the WiFi dongle to your account by scanning the dongle's QR code. After providing some details of the configured system, it may take a few minutes for data to become available. It is possible to add multiple inverters to an account for management purposes, and these can also be shared with other users as required.

The main view is fairly clear and straight forward, with an emphasis on PV generation at the top of the display, but users mostly tend to concentrate on the power flow diagram as a snapshot of what is happening, and using the historical graphs further down for cumulative generation data.

Sunsynk Connect's main plant view, with the power flow diagram usually being of main interest. Naturally, the data is not updated as frequently as on the inverter display itself and you can force an update of the values by refreshing the screen (drag your finger down from the top of the display).

The historical views are very useful to analyse system performance over time, by default displaying data over a day. Selecting a point on the graph shows the values of the 5 key parameters at that point in time.

The graphical generation view includes all the most important parameters required to get a historical perspective of system performance

It is also possible to view summarised data per Month and Year, which give the most useful snapshot indications of overall daily and monthly PV generation, grid import/export and so on. It must be stressed that the grid import/export values are usually obtained using the inverter's CT coil, which is not a metering-grade measurement, and thus the values cannot be used for metering or exact comparisons with your grid-meter consumption numbers for example.

Further, a multitude of inverter status and monitoring parameter data are available, such as battery BMS data, which is useful for diagnostic purposes, as this data is displayed at a smaller interval than the data on the main historical data view. However, Sunsynk limits the duration of data stored per inverter to a maximum of three months, which seems a bit miserly considering it is sometimes useful to go back to the same date a year ago to do data comparisons and that other platforms often store captured data indefinitely.

In Month/Year modes, the cumulative values are show as bar graphs per day/month.

A plethora of predefined and customisable inverter parameters logged at a higher logging resolution are also available.

The App allows you to modify nearly all of the inverter's settings remotely if this is enabled via the inverter touch screen (enabled by default), and if you are the user that captured the plant in your app or have shared the plant with another user with "Manager" permissions. The settings option is available from the options in the top right corner of the plant under the Equipment icon. It would be nice to see some comprehensive descriptions of the settings be included in the app itself.

The main settings view mirrors the icons available on the inverter touch screen

The app is also able to send push notifications to your phone, in case of changes in the state of grid availability. It would be nice to see the selection and scope of these notifications to be expanded, such as sending a notification if the battery SoC drops below a certain value, or if the system is defined with two PV strings and only one string generates any power during the day, potentially indicating a problem.

Overall, the Sunsynk Connect app (and it's web version, available at https://sunsynk.net) is better than the platforms offered by other manufacturers. Most encouragingly, there is ongoing visible or communicated software development, not only in improvements in functionality and fixing of bugs, but also adding new features to the App as well as improvements to the inverter firmware as well. New features such as the new AI-driven enhancements to add intelligence to the monitoring capabilities already in place will continue to make the platform attractive to installers and consumers if they are well implemented and executed. This ongoing development on the software side is to be commended and differentiates Sunsynk from other manufacturers where it appears the conventional approach of software releases, once reaching a deemed "good-enough" point, are largely abandoned. 

Warranty and Support

Sunsynk provides a 5 year warranty for all their inverters and a support network for installers and end-users. They have service centers in major regions that allow for inverter repairs if necessary. The additional of Keith Gough, the Sunsynk company owner, having a strong social media presence, providing technical information and news of developments directly to installers/users does inspire confidence in the company, its direction and the product.

From my own experience, the 5 kW Sunsynk inverter is reliable - of more than 50 installations of this model that I am aware of, I can recall only one instance where an inverter needed to be repaired under warranty after a year or two of operation due incorrect battery voltage sensing which was causing the inverter to shut down spuriously believing the battery voltage was low. Others commissioned more than four years ago are still operating without issue.

However, my experience with attempting to get complex technical questions or issues addressed by their telephonic/email support have not been particularly good, mainly as the front-line support personnel simply do not have the technical expertise to either understand the question or problem and apparently have no avenue to escalate the ticket, possibly to the OEM, Deye, as the in-depth knowledge of the hardware and firmware appears to reside with them. On occasion, sending requests directly to Deye resulted in answers that sometimes were contradictory to what Sunsynk was saying, but turned out to be correct.

This is related to my biggest frustration with Sunsynk and other Chinese inverter manufacturers, which may be related to a language barrier. Official documentation of some less commonly used features and concepts either does not exist or is not concise enough. For example, the process of how to set up a generator to work with a single or parallel inverter arrangement does not have dedicated documentation, with many users and installers having to resort to Facebook groups and online forums to try and obtain answers. Thankfully, due to the inverter's popularity and growing user base, many of the questions have been answered, but some still remain unclear or unanswered and it often up to certain pioneers to simply try things out and "see what happens", hopefully not destroying their inverters in the process.

Conclusion

The Sunsynk 5 kW inverter became one of the most popular inverters in South Africa for  good reason. It offers a compelling blend of reasonable price, features and performance, with a software ecosystem that is continuously developing and improving.

Although it is still sells at a slight price premium of the equivalent Deye inverter, the difference is made up in the superior software implementation in the Sunsynk version. However, there is definitely still room for improvement on the software side, particularly with the inverter user interface - early signs of the upcoming UI changes in the "Acure" interface look very promising.

It would be nice to see an update to the inverter's PV specifications and improved cooling - changes that address the main weak points of the inverter hardware design.

Regardless, I would have no problem recommending the 5 kW Sunsynk to anyone looking for an entry-level solution.

Pros:

• Tried and tested design, good blend of everything you would want in an all-in-one inverter.
• Touch screen user interface makes interacting with the inverter quick and simple.
• Software app and remote monitoring and configuration capabilities are excellent.

Cons:

• More pricey than most of it's competitors
• PV specifications a bit limiting, cooling could be improved.
• User interface quirks and undocumented settings/functions.

I am not sponsored or affiliated with any of the brands mentioned in this review.