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How to buy the best solar inverter

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Do you have an experience with solar power inverters? Share it below.

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A useful read with the updates from the 2018 survey.

We have had two systems installed over the previous 6 months on two different properties.

Re inverters having made a decision for the first property it was simple to go with the same on the second install.

We have Sungrow inverters. Both are dual string, one a 3kW and the other 5kW rated.

Externally they are identical. The units are sealed (spider and dust excluding) and weather proof (IP65 for the tech heads).

The front panel display is useful, once you learn how to use it. Limited instructions in the user manual. CEC and AS approved.

The remote monitoring software has recently been updated. You can use a mobile phone app and or a PC to access the data through Sungrows cloud server. You do need to have the unit supplied with an external wifi module. You can also access the inverter directly through wifi by logging in directly to the inverter.

The neat styling will evaporate once it is surrounded by the connecting conduits, isolation switches and plethora of additional safety labeling added by the installer.

The items to note which may also be generic to other brands.

  1. The inverter local access through wifi uses WEP encryption which is inherently insecure. The inverter generates it’s own SSID which is continuously broadcast. Although you can’t access the Inverter data or settings without the Sungrow App and a login that is unique to each inverter.

The Inverter wifi can be configured to concurrently connect to a home network using more secure WPA, 2.4Ghz 11b/n only from experience.

How great a risk this presents to the home network given the external cloud connection to Sungrow and local WEP Inverter network is not known?

  1. The cloud data logging is reasonably useful. The functionality of the previous version was more techy when compared to the now more consumer orientated product. It is sufficient to monitor overall performance as well as assist with fault finding. There are too many aspects for a short comment here. It however does not backfill any missing data from days where the cloud connection has been lost. The detailed daily data appears to be retained in the Inverter for an extended period (months).

The cloud app and PC software has been reliable and responsive.

  1. Both Inverters appear to perform adequately. They are both installed in full shade in an open environment with good free air movement. The full sealed housing relies on a rear mounted heat sink that stands off the wall slightly plus case for cooling. There is an internal circulating fan that is temperature controlled and appears to cut in when the temperature in the case approaches 60C. The buzzing noise it makes is noticeable up to 5-10m away (against a quiet background). The internal case temperature is logged and can be readily monitored.

It appears that the internal fan and cooling cuts in once the Inverter is heavily loaded and the outside ambient has reached 30-35C.

The one criticism of the product is that the Sungrow promotional literature provided with the quotes advertises an ambient operating temperature maximum of 60C. The tech data sheets supplied with the product and monitoring software reports the 60C limit as the maximum internal case temperature. No doubt the suppliers and installers are aware of this difference. I’ve noted that the current online marketing material still refers to a maximum ambient operating temperature of 60C. However one online document now has a secondary figure that states ‘derating >45C’. It would seem unlikely the Inverters can sustain full rated output on typical Aussie summer day.

To what extent this causes a loss will depend on the installed panel configuration, panel specs and weather on the day. It is worth a broader commentary from the Choice team as to whether the product still meets CEC certification requirements or that there is a flaw in the way the CEC certifies the rating of all Inverters?

As each of our systems have sub-optimal alignments it is difficult without additional data to know for sure if our systems are performing below maximum panel output?

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We have enphase IQ7Plus microinverters for all the reasons shown in the Choice buyer guide as well as similar recommendations on solarquotes.

The system produces within rounding noise of the system’s maximum specification on cloudless days but not as many of those in Melbourne as I would prefer :roll_eyes: Melbourne is what it is cloud-wise.

Enphase has a website and app (MyEnlighten) to monitor output and consumption sent from their EnvoyS management module (requires internet connection). They offer an option to monitor each panel individually but I did not take that up as it is extra cost while the basic system level monitoring is free, and how much is too much information for me as the end user when my supplier included 10 years of panel level remote monitoring at their end, and I am happy for them to do it. Excepting when connected directly to the EnvoyS via its wifi feature it is ‘broadcast only’ so security is not a personal worry.

My EnvoyS is mounted in the back of the breaker box out of sight; the downside is I cannot change the wifi network name or password without a (free) service visit to open the breaker box and internal panel, and press a button. The button enables a wifi connection to it for configuration changes.

The system is only 5 months old so the fact it has not missed a beat so far is to be expected.

edit: a day in the life of our electricity. One can see when we wakeup and turn on the coffee machine, make brekkie, and on this day dinner from the oven as well as our ‘entertainment’ devices. (Average daily production in March was estimated to be 24KWH, the 35.8 KWH at the upper right is the maximum possible for the system, ever, at our latitude.) We have some panels North and some West, hence the asymmetrical profile with the sun slipping behind the houses high up the hill to the west.

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I went with a transformerless inverter, principally because it doesn’t need a fan, because it digitally constructs the AC wave. The fan is typically the first component to fail in an inverter. I’ve seen a video of a leading-brand transformer-based inverter posted by a solar installer, and the fan noise was excessive. Apparently a number of customers have been complaining about the fan noise in that brand’s new range and the manufacturer has refused to do anything about it.

My inverter also has a 12-year manufacturer’s warranty - another draw-card.

I also went with DC optimisers. 2 optimisers out of 16 have already failed and my system is not yet a year old. Such a failure rate is extremely disappointing. The manufacturer replaced the optimisers under warranty and - to their credit - paid for the labour to have the replacement parts installed. I had to prompt the installer a number of times to organise and install the replacement parts. While his labour costs were covered by the manufacturer, there’s not much in it for him to install the replacement parts, hence I guess that’s why he dragged his feet. This was a source of great annoyance to me because I paid an absolute premium for the system, including a premium for the original installation. Having done so, I expected five-star warranty support. Needless to say, I did not provide the installer with an online review after they solicited one from me - it would not have been a glowing endorsement.

However, all in all, the system is exceptionally good. I have individual panel monitoring and can invoke an API to harvest the data generated by the inverter. I also get real-time portal access and generation and consumption data on a mobile app, with options to show graphs with varying aggregation levels.

I oversized the system so - even on the puny 11c feed in tariff - the feed-in offsets the daily supply charge and, through the period from October through to March, mostly offset night-time grid consumption, even with air conditioners running 24/7 during the periods of extreme heat.

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I am somewhat alarmed at the failure rates for inverters. Can anybody explain why?

It looks like reliability is improving. Is it the case that the technology is now mature? If not why not and when will it be so?

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I suspect heat is the biggest killer. Some people add an external fan blowing across the heat sink with a 35C button thermostat on the housing for switching, so that it keeps the unit cooler in hot weather.

I have a couple of extra fans blowing into and across the back of my off-grid inverter, which is frequently subject to summer temps of around 50C in my power shed.

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and humidity.

We have a Fronius IG30 and after 6 years the main control board failed. Under warranty, the service technician indicated that many of the older European designed and manufactured boards are not designed to operate in high heat and humidity environments. He indicated that the high heat and humidity causes corrosion on the main board which results in the inverters failure after a number of years use, especially in subtropical and tropical coastal areas.

Fronius had a fix to the problem which was a replacement main circuit board which was coated in a waterproof coating/resin to prevent moisture penetration to the circuitry. I was surprised that Fronius only replaced those what failed (I understand even well out of warranty) rather than doing a recall as it potentially only affects a small number of older Fronius inverters (in areas as outlined above).

Since the fitment of the replacement main circuit board, we have had no problems.

We have an old transformer inverter with fan and while the fan can be heard when standing close to it, within the house it is inaudible (the inverter is located under the tongue and groove floored house. One thing we do notice is the timber floor immediately above the inverter (about 700 above the top of the inverter) get warm. A benefit in winter but not so in summer.

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The core technology is likely very mature. Especially considering the extent to which similar elements of the same technology have been used in industry for a long time. EG Variable speed motor drives which synthesise variable AC power (voltage and frequency).

Like all solid state and electrical technology it will continue to be evolve.

Issues around reliability are more likely to come from manufacturing decisions relating to cost minimisation.
Quality of components, assembly and testing!
Or specification and design margins!

Is the market mature might be the alternate question?

A second question might be, is anyone in a position to reliably collect all the data relating to Inverter failures?

Or how relevant might some of this data be in a few years time anyway?

P.s. My take is that Inverters have a less than five year technology life span, despite the hardware potentially lasting a decade or longer. One option Microinverters have the potential (through manufacturing volume and technology improvements) to fall in cost to displace the now common string inverters.
There is an excellent example in LED lighting where there was once a need for external power supply block, and a high purchase cost. Now for less than $5 you can get a LED globe the same as any other globe with the electronics built in. They get cheaper each time I look.

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Re excessive fan noise, here are a few of the comments from installers on the Facebook page. (I’ve selectively snipped comments because the language can be a bit ripe in that group.) Fan%20noise%201 Fan%20noise%202 Fan%20noise%203 Fan%20noise%204

My transformerless inverter doesn’t make a sound.

Regarding heat: I had the inverter mounted in the garage. I didn’t want it out the front of the house (on the south side) next to the meter box, as I didn’t want anyone to have casual access to it, to be able to turn off the power supply to the house. The garage is on the west side of the house, is shaded by the adjacent fence and building, has a high pitched roof and its interior temperature remains comfortable in summer. When the solar system is generating close to its peak capacity on a hot day and I place my hand on the metal plate near the back of the inverter, it is quite warm. There’s a decent interior wall cavity between the inverter position and the house - I don’t notice any heat transfer to the house, fortunately.

Incidentally, that “Crap Solar” Facebook group was one of the sites I monitored while I was making a decision as to what system and installer to go for, so I could learn about system design and installation problems to inform my choice.

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Position may be a factor. During the sales process one installer, who came onsite to inspect my property for a quote, told me that the inverter only starts derating at 50 degrees celsius and could happily tolerate a location on the north-facing exterior wall of my house. I culled that installer from my selection process because I can’t imagine a north-facing exterior wall in the baking sun with no shading, no eaves and no shelter ever being a good choice for inverter location! I didn’t trust their judgement on system design.

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@margotk, you have made some interesting observations.

I too rejected any offer to install our inverters externally in full weather and exposed to heating from the sun.

Re fan noise, my research suggests that modern transformerless Inverters may also use cooling fans! The Fronius Primo 5 you have referenced is a transformerless design. It has temperature controlled forced ‘adaptive cooling’.

https://www.fronius.com/en/photovoltaics/products/all-products/inverters/fronius-primo/fronius-primo-5-0-1

Sungrow the brand we have is a transformerless design Inverter and also has a cooling fan internally.

Older inverters had ventilated designs with forced cooling. They also required a transformer to couple the Solar Power to the household power and grid. Modern design domestic Inverters do not require the transformer. The need for a cooling fan/s depends on other design decisions that are unrelated. Cooling fans are common in higher powered and three phase Inverters.

P.s. What is disappointing is that the data sheets for the Fronius linked above and that for the Sungrow do not have a noise level specification or rating. The internal fan in our two Sungrow Inverters is similar in noise level to a fridge. It only operates on hotter days.

This suggests you cannot rely on the product marketing, design (transformerless), or quote to inform you if an Inverter is 100% silent in operation. It is a question you need to ask and receive a written assurance on. The same may apply to temperature derating (potential loss of output on hot days). Both of these are technical issues the average consumer should be properly informed on in any quote. And whether the supplier has made allowance for any loss of average output.

Although some of us might suggest the product is not fit for purpose and demand a product replacement or refund.

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Stating the obvious for those who are noise sensitive or worry about inverter location re sun and heat, microinverters are located on the roof, one under each panel. That is where they are designed to be. Totally quiet as well as out of sight and reach for the typical miscreant who might be tempted to interfere. :slight_smile: Then there are the ‘toys’ in the breaker box though.

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Very edifying Mark. Thanks for the info!

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I’ve got an SMA Sunny Boy - mounted on the outside wall of my house in arguably a hotter place than most of the country. No humidity though - thankfully.

Aside from the fact SMA take their coding standards a little recklessly (done in China now days I suspect, like their hardware) it has been a quiet and efficient little red barnacle on my wall, and I no longer pay for power. Indeed over $700 in the black, even after summer …

QED.

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Can you (or your estate) ever claim that back as a payment? With interest? Or at ‘the end of the story’ does it become a donation?

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I believe it is once per year the credit can either be paid to the customer or applied to another account with the energy retailer. With winter coming and the swampy going into hibernation I’ll consider cashing it out soon …

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Sounds great, and all those benefits of living far from the coast!

Perhaps the rest of the nation could move to natural gas and diesel, and get the benefits of the same great feedin tariffs?

Not a coal fired power station required. :partying_face:

P.s. needs a tongue in cheek emoji?

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Our new solar & battery system uses a Sungrow SH5K-20 inverter which is mounted on the western wall of our home along with the LG RESU 10 batterey and the Sungrow back up box.

They are below the eave and we have a 3.5 metre high hedge on the side boundary 2 metres away from the equipment so that it is only in direct sunlight for a short time in the mid-afternoon.

I have occassionally heard the fan start up in the inverter but it is not a problem, and I have not seen the battery temperature exceed 33 degrees even when it is being force charged due to overcast conditions.

We had originally planned to have it all installed in the garage but the QRIDA changed the requirements for the Qld Solar Bonus Scheme so that we would have had to install a bulky and unsightly bollard near the battery so as to prevent it being struck by a vehicle.

A house hallfway down our street has a Sunny Boy inverter mounted on the eastern wall with no natural shading and they have a potato sack hanging in front of it which is affixed to the split aircon outdoor unit, so presumably they have had a problem.

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Yes, if your energy account is in credit, you can request and receive a refund from the retailer.

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In the case of my inverter failing (requiring a replacement), it was not heat. I harvested all of the inverter’s operational logs - including temperature readings - using the API and there was nothing in the data to suggest a root cause of the failure. The inverter is installed in a protected location, is not exposed to the elements nor excessive heat and is well ventilated.