Are micro-inverters/ AC battery tie the way to go currently?

[BentleyJ]

I do know a friend of mine went Enphase micros on 34 panels the same time I put in my SMA gridtied inverter. 33 warranty replacements later it’s finally slowed down. My SMA never had a screw removed.

That is not normal at all. I have 11 x M250's running since 2018 not a single problem or failure.

 

[DIYrich]

It is not complexity that kills electronics. With inverters it is heat that will kill them. Because string inverters deal with higher voltages and more current they are more likely to over heat. String inverters also have moving parts like fans that can fail (and yes lead to over heating). They will bring dust into the units that can cause over heating because it builds up and becomes a thermal insulator. Dust can also be conductive and cause shorts. Micro inverters are sealed and potted (meaning they put material around the electronics that conducts heat but not electricity). They are not affected by the accumulation of dust. They have no moving parts. This is why micro inverters are far more reliable than string inverters.

So rather than looking at something rather arbitrary like complexity, you should be looking at real world failure rates. That's what matters. A fan may be simple, but it will still fail far more often then an integrated circuit with millions or even billions of transistors. How often do cell phone electronics die before the cell phone battery? Do you thing a battery is more complicated than all the electronics?

Your original statement was: "Because of rapid shout down requirements any new system is going to have some type of panel level electronics anyway." implying that RSD is as likely to fail as a micro inverter.

My point is that RSD (can be a simple circuit - that does not generate heat) is not comparable to a Micro Inverter.

Also, I'm happy to parts change at ground level. Not so thrilled about doing it on the roof.

 

[629658]

That is not normal at all. I have 11 x M250's running since 2018 not a single problem or failure.

Well all I can say is Enphase replaced all but one over 7-8 years. They didn’t all fail at once but I am able to see his system and for a while it seemed he always had one or two out awaiting replacement. He was an early adopter so he had 1st gen. They are better now but as I said during the same time period I had zero down days he had many. I don’t think anyone can say with a straight face micros are more reliable than a quality string inverter.

 

[BentleyJ]

I don’t think anyone can say with a straight face micros are more reliable than a quality string inverter.

Agreed, our other PV system is a 12 panel DC string connected to a Fronius IG Plus. 12 years and still working perfectly. The reason I went with microinverters for the second system was because the 11 panels are split up on 3 roofs areas. Azimuth and tilt are all different, this is where microinverters really are a good option.

 

[629658]

I do know a friend of mine went Enphase micros on 34 panels the same time I put in my SMA gridtied inverter. 33 warranty replacements later it’s finally slowed down. My SMA never had a screw removed.

One other issue as I see it micros sit in extreme heat and cold their entire lives. My equipment is in a temperature stable environment and out of the weather.

 

[629658]

Agreed, our other PV system is a 12 panel DC string connected to a Fronius IG Plus. 12 years and still working perfectly. The reason I went with microinverters for the second system was because the 11 panels are split up on 3 roofs areas. Azimuth and tilt are all different, this is where microinverters really are a good option.

Completely agree there are places micros work well and I still may add a few at a later date. But there are issues with all AC coupling and storage in grid out situations that don’t seem to be resolved to my satisfaction. A good mix of both AC and DC coupling seems to resolve the issues

 

[Ampster]

I’m not sure I buy that.

I agree, an EVSE is basically a relay with a protocol to tell the onboard charger what Amperage to pull. Nothing like UL1741SA &SB compliance. Once connected an EVSE has no communication responsibilities and the pilot signal does the disconnect when the trigger is pulled.

 

[629658]

Micro’s definitely handle shading better

 

[629658]

That is not normal at all. I have 11 x M250's running since 2018 not a single problem or failure.

He was in the game way earlier. I’m sure it’s better now. None of his replacements have failed so far but I am/was concerned for him.

 

[wheisenburg]

Your original statement was: "Because of rapid shout down requirements any new system is going to have some type of panel level electronics anyway." implying that RSD is as likely to fail as a micro inverter.

My point is that RSD (can be a simple circuit - that does not generate heat) is not comparable to a Micro Inverter.

Also, I'm happy to parts change at ground level. Not so thrilled about doing it on the roof.

Here are some stats from one installer. I couldn't find any published reliability rates from Solar Edge (no surprise on that). Now there are other inverter companies, but at least here in the USA, Enphase and Solar Edge have by far the most of the market share. Remember that Enphase reliability is a failure rate of 0.05% over a five year period. Notice that the rate of failure of solar edge optimizers is actually 40 times higher than that of Enphase Micro inverters. So obviously the complexity of the circuits has very little to do with failure rates. What is far less important is the quality of the design and manufacturing. Remember these micro inverters are sealed. They have no fans or moving parts. They are designed and built to survive rain, snow, heat and cold.

I would agree that it might be easier to change out a string inverter, but for people that are not serious DIYers, they may not want to work with high voltage DC wiring whether it is on the roof or in the garage. They are going to have to wait, possibly for months to get an inverter changed. The solar installers around here are booked months in advance for highly profitable new system installs. I doubt that solar companies are going to ask their installation customers to wait longer while they go swap out a bad inverter on a warrantee contract for a couple hundred bucks.

SOLAREDGE OPTIMISER FAILURES​

Here are MC Electrical’s updated SolarEdge failures as of December 2020. It has been 6 years since our first install.

• 130 SolarEdge systems installed since Nov 2015
• 138 inverters installed
• 3293 optimisers installed
• 75 approved optimiser warranties
• 36 approved inverter warranties
• 1 rejected inverter warranty (SE claimed lightning with no evidence).

So percentages work out as a whopping…

• 2.2% optimiser failure rate
• 27% inverter failure rate

 

[DIYrich]

Here are some stats from one installer. I couldn't find any published reliability rates from Solar Edge (no surprise on that). Now there are other inverter companies, but at least here in the USA, Enphase and Solar Edge have by far the most of the market share. Remember that Enphase reliability is a failure rate of 0.05% over a five year period. Notice that the rate of failure of solar edge optimizers is actually 40 times higher than that of Enphase Micro inverters. So obviously the complexity of the circuits has very little to do with failure rates. What is far less important is the quality of the design and manufacturing. Remember these micro inverters are sealed. They have no fans or moving parts. They are designed and built to survive rain, snow, heat and cold.

I would agree that it might be easier to change out a string inverter, but for people that are not serious DIYers, they may not want to work with high voltage DC wiring whether it is on the roof or in the garage. They are going to have to wait, possibly for months to get an inverter changed. The solar installers around here are booked months in advance for highly profitable new system installs. I doubt that solar companies are going to ask their installation customers to wait longer while they go swap out a bad inverter on a warrantee contract for a couple hundred bucks.

SOLAREDGE OPTIMISER FAILURES​

Here are MC Electrical’s updated SolarEdge failures as of December 2020. It has been 6 years since our first install.

• 130 SolarEdge systems installed since Nov 2015
• 138 inverters installed
• 3293 optimisers installed
• 75 approved optimiser warranties
• 36 approved inverter warranties
• 1 rejected inverter warranty (SE claimed lightning with no evidence).

So percentages work out as a whopping…

• 2.2% optimiser failure rate
• 27% inverter failure rate

Since you quote Solaredge Optimiser Falures, here is a link to Enphase by the same company.
4% of Enphase jobs have had a failure in 5 years of installing them. 0.18% microinverter failure rate in 5 years of installs (vs the 0.5% over five years you quoted). Their experience of failure rate after 5 years may be even higher since not all installed systems have reached the 5 year age. I also read something about the IQ7's having problems, which may skew recent results.

Enphase Micro-Inverter Review

Enphase microinverters are reliable, but are they the best shade solution? This review analyses the pros and cons of Enphase for solar panels, including shade performance, voltage rise, and monitoring issues.

www.mcelectrical.com.au

Edit: Interesting read linked to in the article about Solar Voltage Rise. For Microinverters, the voltage rise is at the roof. For String Inverters, the voltage rise is at the inverter that is directly plugged into the Grid. Less distance, less rise (or need to oversize wire to reduce the rise).

 

[wheisenburg]

Completely agree there are places micros work well and I still may add a few at a later date. But there are issues with all AC coupling and storage in grid out situations that don’t seem to be resolved to my satisfaction. A good mix of both AC and DC coupling seems to resolve the issues

I agree that adding battery storage to an existing micro inverter grid is not a good solution (I know because that's what I have). If you want a system that can actually charge your batteries both on and off grid, then a DC coupled hybrid inverters is the only thing that currently works well. A possible exception is a full Enphase grid and battery system. These are very expensive to install.

 

[wheisenburg]

Since you quote Solaredge Optimiser Falures, here is a link to Enphase by the same company.
4% of Enphase jobs have had a failure in 5 years of installing them. 0.18% microinverter failure rate in 5 years of installs (vs the 0.5% over five years you quoted). Their experience of failure rate after 5 years may be even higher since not all installed systems have reached the 5 year age. I also read something about the IQ7's having problems, which may skew recent results.

Enphase Micro-Inverter Review

Enphase microinverters are reliable, but are they the best shade solution? This review analyses the pros and cons of Enphase for solar panels, including shade performance, voltage rise, and monitoring issues.

www.mcelectrical.com.au

A failure of one panel over five years is not that big of a deal. I have 35 panels. I can run for months without one panel and still be ok. If you take this guys stats as accurate, I still would have a 7 times greater chance of losing my entire system with Solar Edge than losing a single panel with Enphase.

 

[629658]

Here are some stats from one installer. I couldn't find any published reliability rates from Solar Edge (no surprise on that). Now there are other inverter companies, but at least here in the USA, Enphase and Solar Edge have by far the most of the market share. Remember that Enphase reliability is a failure rate of 0.05% over a five year period. Notice that the rate of failure of solar edge optimizers is actually 40 times higher than that of Enphase Micro inverters. So obviously the complexity of the circuits has very little to do with failure rates. What is far less important is the quality of the design and manufacturing. Remember these micro inverters are sealed. They have no fans or moving parts. They are designed and built to survive rain, snow, heat and cold.

I would agree that it might be easier to change out a string inverter, but for people that are not serious DIYers, they may not want to work with high voltage DC wiring whether it is on the roof or in the garage. They are going to have to wait, possibly for months to get an inverter changed. The solar installers around here are booked months in advance for highly profitable new system installs. I doubt that solar companies are going to ask their installation customers to wait longer while they go swap out a bad inverter on a warrantee contract for a couple hundred bucks.

SOLAREDGE OPTIMISER FAILURES​

Here are MC Electrical’s updated SolarEdge failures as of December 2020. It has been 6 years since our first install.

• 130 SolarEdge systems installed since Nov 2015
• 138 inverters installed
• 3293 optimisers installed
• 75 approved optimiser warranties
• 36 approved inverter warranties
• 1 rejected inverter warranty (SE claimed lightning with no evidence).

So percentages work out as a whopping…

• 2.2% optimiser failure rate
• 27% inverter failure rate

I’m not sure who you are dealing with but I had a licensed electrician come to my house and install my AIO. I did not wait 3 weeks for anyone. Replacing an existing inverter would be 100% within their capacity and waiting for a Solar installer is unnecessary. So I think that point is incorrect.

 

[629658]

A failure of one panel over five years is not that big of a deal. I have 35 panels. I can run for months without one panel and still be ok. If you take this guys stats as accurate, I still would have a 7 times greater chance of losing my entire system with Solar Edge than losing a single panel with Enphase.

Same panels as we started with 10 yrs ago. Working great. Micros have their place but give me central string inverter anytime. That being said, adding a few micros and some AC coupling would be a nice cheap way to increase PV production.

 

[wheisenburg]

I’m not sure who you are dealing with but I had a licensed electrician come to my house and install my AIO. I did not wait 3 weeks for anyone. Replacing an existing inverter would be 100% within their capacity and waiting for a Solar installer is unnecessary. So I think that point is incorrect.

That is good to hear. Some inverter companies require that you be certified to install their product or they won't let you commission the system. Also if you want the work done under a warrantee, there might be restrictions on who you are allowed to use (only authorized dealers). But since I am a DIY person, I don't really have to worry about such things. I watched a couple Youtube videos and now I am a freaking expert on all things solar. Give me a wrench and a pair of wire cutters and I'll "Giter" done.

In my area (PA) there is a backlog for just about any kind of skilled construction work. Solar is one of the worst (3-4 months min). Getting a standby generator serviced under warrantee is also a huge issue around here. Generac wants someone in their dealer network to do all the warrantee work.

 

[Hedges]

Here are some stats from one installer. I couldn't find any published reliability rates from Solar Edge (no surprise on that). Now there are other inverter companies, but at least here in the USA, Enphase and Solar Edge have by far the most of the market share. Remember that Enphase reliability is a failure rate of 0.05% over a five year period. Notice that the rate of failure of solar edge optimizers is actually 40 times higher than that of Enphase Micro inverters. So obviously the complexity of the circuits has very little to do with failure rates. What is far less important is the quality of the design and manufacturing. Remember these micro inverters are sealed. They have no fans or moving parts. They are designed and built to survive rain, snow, heat and cold.

Solar Edge is not representative of the reliability of other string inverters.

SMA and Fronius are two big names, but I don't know what market shares are now.
Some 20 years ago when CEC rebates were available, their list of installed systems was > 50% SMA, < 50% shared by 20 other companies.
My own reliability calculation was 34 years MTBF, from 5 (later reduced to 4) SMA SWR2500U inverters operated over 17 years, with 2 failures.

Solar Edge - an installer's blog

Came across the following blog. It includes the company's installed system numbers and failure rates for SolarEdge, Fronius, Enphase. Also, information on limitations and best use of optimizers. https://www.mcelectrical.com.au/solaredge-inverter-optimiser-review/

diysolarforum.com

(Some people defending Solar Edge's reliability even after all data given in that thread.)
One metric I came up with is ratio of "for part or repair" vs. "Used" listings on eBay. Very telling.

I agree, quality of design and manufacturing.
Environment (including heat) affects life, so Enphase has to design for a more hostile environment.
Whether the fans run (in my newer inverters) depends on temperature, and if not running the output power will be derated (but would run at upper end, impacting life.) The electronics is NOT exposed to dust in these inverters. That compartment is sealed 4x. Only fans and transformer are 3R.

 

[Ampster]

The biggest failure I have experienced on my own and a friend was the impact of power surges on micros. Ever since then I have always put a surge suppressor on the main panel. Most of my micros go through the gen port of my SolArk so there is additional protection there.

 

[wheisenburg]

Solar Edge is not representative of the reliability of other string inverters.

SMA and Fronius are two big names, but I don't know what market shares are now.
Some 20 years ago when CEC rebates were available, their list of installed systems was > 50% SMA, < 50% shared by 20 other companies.
My own reliability calculation was 34 years MTBF, from 5 (later reduced to 4) SMA SWR2500U inverters operated over 17 years, with 2 failures.

Solar Edge - an installer's blog

Came across the following blog. It includes the company's installed system numbers and failure rates for SolarEdge, Fronius, Enphase. Also, information on limitations and best use of optimizers. https://www.mcelectrical.com.au/solaredge-inverter-optimiser-review/

diysolarforum.com

(Some people defending Solar Edge's reliability even after all data given in that thread.)
One metric I came up with is ratio of "for part or repair" vs. "Used" listings on eBay. Very telling.

I agree, quality of design and manufacturing.
Environment (including heat) affects life, so Enphase has to design for a more hostile environment.
Whether the fans run (in my newer inverters) depends on temperature, and if not running the output power will be derated (but would run at upper end, impacting life.) The electronics is NOT exposed to dust in these inverters. That compartment is sealed 4x. Only fans and transformer are 3R.

In the Schneiders they also separate the cooling air that flows over heat sinks and the transformer from the electronics compartment. They say their battery inverters are designed to last decades.

So it is not really an issue of string vs micros. I think there are very reliable charge controllers. It is more a matter of proper design. My biggest gripe is that getting micros to work AC coupled off grid is not straight forward. I think the reliability and efficiency of micros for grid tied systems is great. People just need to be aware that adding solar backup to these micro inverter systems will be a challenge. I've considered adding a charge controller to create a 65/35 AC/DC system. The problem then would be you might then need to actually export from both the micro and the battery inverter. Too complicated.

Given the rarity of of power failures in my area, I may just hook up my contactor up to disconnect the PV when there is no grid power. I'm not at that point yet, but I am also not convinced that the system can properly control the PV power when the grid is down.

 

[629658]

In the Schneiders they also separate the cooling air that flows over heat sinks and the transformer from the electronics compartment. They say their battery inverters are designed to last decades.

So it is not really an issue of string vs micros. I think there are very reliable charge controllers. It is more a matter of proper design. My biggest gripe is that getting micros to work AC coupled off grid is not straight forward. I think the reliability and efficiency of micros for grid tied systems is great. People just need to be aware that adding solar backup to these micro inverter systems will be a challenge. I've considered adding a charge controller to create a 65/35 AC/DC system. The problem then would be you might then need to actually export from both the micro and the battery inverter. Too complicated.

Given the rarity of of power failures in my area, I may just hook up my contactor up to disconnect the PV when there is no grid power. I'm not at that point yet, but I am also not convinced that the system can properly control the PV power when the grid is down.

I think you’re right and I get caught up in it myself. Our grid power is extremely reliable. It’s kind of like preparing for an EMP thing.