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Review of the MPP Solar MKI4K Hybrid Inverter and Support

TL;DR - Never buy a MPPSolar Inverter!



We bought the MPP Solar MPI4K Hybrid Inverter from their authorized reseller maximum_solar via their store on ebay.
It cost us 1260.48 Euros , due to delays it took almost a month to arrive from Germany and for this we got a 50 Euro discount.
When the inverter finally arrived we plugged it into our 3000w solar array of 12 x 250w panels.
In this configuration it worked for six months without a problem.

This summer we rewired our solar panels , instead of two disparate arrays ( 2000w and 3000w ) we now had two identical arrays of 2500w each.
According to the website and manual the MPI4K inverter is rated at a maximum of 5000w of solar power using two strings of ten panels.

4.65 KW from the solar panels
4.65 KW from the solar panels


Now connected to the 2 x 2500W solar arrays the inverter worked for a single day , when we came home later the inverter was screeching and showing 'Error 03'.

I contacted MPP Solar Support , filled in their spreadsheet with all the details and sent photos of the failed Q8 and Q7 mosfets that we could see.

Failed Mosfets Q8 and Q7 in the DC-to-DC board of the MPP Solar MPI4K Inverter
Failed Mosfets Q8 and Q7 in the DC-to-DC board of the MPP Solar MPI4K Inverter

We were told that the boards inside needed to be replaced , new boards would be sent out and that we would have to install them (?!).


We could see that this repair process was going to take some time so we ordered a second identical inverter.
This would allow us to get back on solar power as soon as possible, later we could spread the load using the two inverters connected in parallel.


We got the second inverter setup and working.


The replacement boards duly arrived.
As the unit is under a year old and under warranty the exchange boards were free , but we still incurred an 80 dollar postage charge from Taiwan and a 38 Euro tax bill from the delivery driver. Nice.
From their support website - "In exchange, customer will agree to a small charge to cover postage of the replacement board or parts."
Odd how the purchase on eBay included free delivery for the entire inverter yet carriage for two boards is 100 Euros.
Over the next week I fitted the two replacement boards into the inverter case and carefully reconnected all the cables.


This morning we took the repaired inverter and put it back in place to tested it.
Thankfully I only plugged it into the mains electricity , not the load (our house) or the solar panels.
Unfortunately after a few seconds there was a loud pop and the display shows 'Error 03' again.

290V AC and the dreaded 'Error 03' again.
290V AC and the dreaded 'Error 03' again.

You can see in this photo that the AC grid value is showing 290V AC , unlikely a true mains electricity voltage reading - more likely a problem inside the inverter , this could explain why it blew up again.

After removing the top and sides of the case again I saw that the component QC1 on the AC input board has failed and exploded.

Another component failure in the MPP Solar MPI4K Inverter
Another component failure in the MPP Solar MPI4K Inverter


Support have replied after the weekend , I have sent details and the photo of failed component QC1.


Support replied , asking for the same photo and the 'unit current situation' ?!

unit current situation ? - waiting for a month to be fixed!
Unit current situation ? - waiting for a month to be fixed!


eBay Review of the MPP Solar MPI4K Hybrid Inverter
Left negative feedback on eBay with a link back to this review.
"Sub-standard inverter , Terrible Support, Review at (which links back here)."


Mailed Peggy Hung in Sales and Support again as there is no progress.


Got a reply from Peggy Hung - "will pass on to Support"


Our brand-new MPI4K inverter just exploded , I removed it and checked inside for damage , once again it is the mosfets on the DC to AC board , more damage this time though.
We were only using a single solar string so the input could not have been more than 2500W , I checked it about an hour earlier and the panels were generating about 1200W.
After the failure I checked the voltage of the string - 300V DC , well within the tolerance of the inverter.


A week has passed with no reply from Support yet their site promises "general response time is within 48-72 business hours".
Today I sent a mail asking for Managers contact details.
Sent Support the IFFR spreadsheet and photos of failed mosfets , see below for the same.

Exploded mosfets from our second MPP Solar MKI4K inverter
Exploded mosfets from our second MPP Solar MKI4K inverter

Exploded mosfets from our second MPP Solar MKI4K inverter
Exploded mosfets from our second MPP Solar MKI4K inverter

Exploded mosfets from our second MPP Solar MKI4K inverter
Exploded mosfets from our second MPP Solar MKI4K inverter


Receive a mail from Support asking for details I had sent them earlier.


I have sent details of the technical specifications of our solar panels :-
* Pmax = 250 W * Vmp = 30.5 V * Imp = 8.20 A * Voc = 37.9 V * Isc = 8.57 A

technical specifications of our solar panels
Technical Specifications of our solar panels


MPP Solar Support finally reply apologising and prioritising our cases , also tells me he is proposing our cases to his manager.


Checked eBay and of course even our latest inverter purchase is out of the available Return period and not covered by eBays guarantees. Nice.


Our two support issues have been ignored for another week. Sent another mail asking to be put in contact with a Manager.

Support replied later in the day , supposedly the MPI4K inverter is getting replacement special boards which need to be carefully tested before being dispatched.
This part of the email looks like an admission of guilt - "In order to avoid the error still appear again after replace the board, we will provide the new board to you."
Asked why our two inverter failure issues haven't been passed on to a Manager.


I noticed this wonderfully laughable paragraph on their AliExpress website :


TRUST:the best customer is a repeating customer.
We want to gain your trust, by helping one customer at a time.
We are not interested in being the Price Leader of the industry, but we want to be the Trust Leader.


Mailed Support asking how long the new special boards are going to take to be tested and sent , also asked why these two issues haven't been passed on to a Manager.


Disgusted by the lack of progress by MPP Solar , we ordered a new GroWatt 5000 MTL inverter from MidSummerEnergy.


The new GroWatt 5000 MTL inverter has arrived.
I plugged this inverter into the same two 2500W strings of solar panels - no explosions , no problems.


No contact with the MPP Solar support team for over 20 days , this is how not to handle support.


No contact from MPP Solar for over a month now.
A german gentleman contacted and informed me of PayPal's Resolution Centre 180 day time limit. Thanks!
Started a PayPal dispute (PP-006-308-133-151).

MPP Solar Inc,
We purchased this inverter but within three weeks it failed.
I have sent you all the details and photos of the damage as requested.
Serial Number = 96121701100012
This is the second inverter we have bought , it is a replacement as the first inverter also failed.
So we now have two failed inverters awaiting replacement or repair , both under a year old.
A month has passed since you promised the upgraded motherboards with no communications from you.
We have completely lost trust in the quality of your inverters and would like to be refunded.
I am documenting the whole series of events at
Looking forward to hearing from you.
Mark Waters
- Mark Waters, Monday, 6 November 2017 at 07:28:40

Wow , the PayPal Resolution really seems to work , I got a reply in less than two hours instead of the usual days!

Hello Mark,
Sorry to hear that and we will try to expedite the issues with RD for MPI 4K, but leaving these reviews and negative feedback does not help, as we still need time to resolve the technical problem, which requires research and testing in the lab.
The new version boards with new updates are scheduled to be ready around middle of November.
However as you have expressed wish to return for refund and also opened a Paypal case the only course left would be for you to return this and a Paypal refund.
But if you still wish to receive the new boards, we will send to you after you have closed the dispute.
please advise you decision which way to proceed.
- MPP Solar Inc, Monday, 6 November 2017 at 09:23:24

As I am believe we have waited long enough I am asking for a refund of both inverters.

My feedback and reviews have always been honest which is why I am happy to post it publicly.
If our experience with MPP Solar had been positive then so would the reviews.
You have had *months* to resolve the issues with your manufacturing process and component quality , while we waited with failed equipment.
Please remember that we have already paid over 100 Euros for *free* replacement boards for the first inverter which also blew up immediately !
I understand that electronic devices fail , to have kept me as a happy customer you only needed to replace the failed units promptly and communicate with me.
To resolve our issue I would like to return both failed inverters and be refunded.


Our GroWatt 5000 MTL inverter has been running without an issue for four weeks now.
It is plugged in to the same 2 x 2500W solar panel arrays.

MPP Solar have gone quiet again.

Time Passes - We have waited so long for Support that our inverters are literally gathering dust

Time Passes - We have waited so long for MPP Solar Support that our inverters are literally gathering dust.


Cleaned the dust off both the failed MPP Solar inverters , packed them back into their original boxes.

Two failed MPP Solar inverters ready to be packaged and returned


Another week passes , no progress on the PayPal dispute from MPP Solar , so I have asked for details to return the faulty inverters and be refunded.

No response after a week.
Please can you give us returns numbers for the TWO failed inverters.
Their Serial Numbers - Paypal Transaction IDs - Value are :-
1. 96121608100145 - 7PG29298XV052211G - 1099 GBP
2. 96121701100012 - 0WX509659M289481L - 999 GBP
We will also need the returns address for these units.
- Mark Waters, Tuesday, 14 November 2017 at 08:24:09


A few hours later , a response.

This is 1 transaction, not two. Return address is:

- MPP Solar Inc, Wednesday, 15 November 2017 at 04:47:27

So we replied :-

I understand this PayPal dispute is addressing just the second inverter.

Would you be willing to refund us for both of the failed inverters we have purchased ?
If so we will happily return both inverters and the extra boards , all of which is in good condition.

If however you are unwilling to refund us for the first inverter what is to become of it ?
We have already paid 10% of its value again for replacement boards which also failed.
These replacement boards were for the first inverter and will only be returned with that device , please don't try and confuse the issue.

- Mark Waters, Wednesday, 15 November 2017 at 07:54:16


Good News - Our GroWatt 5000 MTL inverter has been working without a problem for six weeks now.
In that time we have generated over 530 KW!

Got carriage quotes to return faulty MPP Solar inverter2 and replacementboards1 using TNT
192.35 Euros - TNT Carriage cost for failed mpp solar inverter2 on 2017-11-22
91.65 Euros - TNT Carriage cost for failed mpp solar replacementboards1 on 2017-11-22

No response from MPP Solar via PayPal dispute in over a week again , time to nudge the dispute forward again.

Another week passes with no response.
Please send us the Returns Numbers for failed Inverter2 and ReplacementBoards1.
As per your own 'Reciever Pays Carriage' Policy , you need to send us the carriage costs to return faulty Inverter2 and ReplacementBoards1.
Inverter2 via TNT = 192.35 Euros
ReplacementBoards1 via TNT = 91.65 Euros
Screenshots of carriage pricing available at
- Mark Waters, Wednesday, 22 November 2017 at 07:31:16

Got a reply within an hour this time!

You are mistaken for the return postage. This will done at your own cost. not us.
Up until this point, we do not know what you did to those new boards and why they failed again.
They were supplied to you under warranty free of charge and FULLY tested before we sent to you.
Then they failed again after you installed them.
We have a zero tolerance for any kind of malicious threat or review done to take advantage of our service and company name and frankly what you have done is so by making it personal.
It was explained to you we could and would be willing to send you another set of new boards provided you can guarantee there's no foul play, but you decilned and insisted on return.
- MPP Solar Inc, Wednesday, 22 November 2017 at 08:14:11

So I replied :-

It is likely that the replacement board failed because it was connected to an existing damaged board.
Why were we sent only one board ?
If both boards had been replaced then it should have worked like a brand new inverter.
However , the replacement board was for inverter1 , again , you are trying to confuse this issue.
This dispute is about inverter2 , which lasted less than a month and was bought in good faith while we waited for you to repair inverter1.
We have since bought a third inverter from different company which is working perfectly on the same solar panels.
In the six weeks since it was installed we have generated over 530 KWH.
Throughout this whole episode we have been completely professional , honest and transparent.
- Mark Waters, Wednesday, 22 November 2017 at 09:23:09

Escalating this to Paypal soon as this dispute expires in four days and we are no further forward.


MPP Solar didn't even bother replying again , so today I escalated the dispute to PayPal.
Here is our letter :-

This dispute is about Inverter2 which we purchased while we trusted Inverter1 would be repaired.
Inverter2 lasted less than 30 days before exploding.
Since then we have repeatedly asked for support , MPP Solar barely respond and when they do we are fobbed-off with stories of board improvements coming mid-November supposedly.
I am not sure what more we could have done.
We bought two inverters - both exploded.
We have paid for replacement boards for inverter1, also exploded.
We have waited months.
We have repeatedly asked to speak with a Manager but have never been contacted.
We have been falsely accused of malicious threats.
The solar panels have been tested by an engineer - no problems found.
We purchased a third inverter from a different company which works perfectly on the same solar panels.
We are resigned to the fact that we've already lost 1300 Euros as inverter1 will unlikely ever be repaired.
This dispute is our final recourse to recover some of our money.


We recieved an email this morning , unsurprisingly PayPal have decided this dispute in favour of their most profitable client - MPP Solar.
Here is the mail :-

Dear Mark Waters,
We've completed our review and unfortunately are not able to decide this case in your favor.
We are unable to take any action on this case because it is not covered under PayPal Purchase Protection.

So , there we go.

Over 2500 Euros spent via PayPal and Ebay and the items are not covered with any sort of protection scheme.

MPP Solar screwed us.
EBay screwed us.
PayPal screwed us.


A visitor from IP address visited this site today , this IP Address belongs to PayPal Inc range.
Interesting how they visited this write-up after deciding against us and not before, even though I posted the URL in the dispute notes.
Just grep'ed the webserver log files and that was PayPal's first visit.


Wondering what to do with our two failed MPP Solar inverters now , we are obviously never going to get any support from MPP Solar themselves.
Would it even be worth replacing the exploded components ?
I don't trust the hardware / design / component quality.
Could I replace the failed components with higher quality devices ?
Any advice would be appreciated. Thanks.


The GroWatt 5000 MTL inverter has been running without issue (or noise) for two months now, twice the uptime of the MPP Solar MPI4K.
In that time it has generated 670 KwH of power , not bad for a cloudy and foggy winter.


The GroWatt 5000 MTL inverter has been running without issue (or noise) since 2017-10-11 , just over 8 months now , in that Winter / Spring season it has generated 2975 KWH of power.

So after six months with no contact from MPP Solar we got an email today that started with :-

"First please accept our sincere apologies for the problems that these inverters have caused you".

... and continues with :-

"After months of extensive testing in the lab and exchange with our supplier, we have been working hard on investigating this issue and found that it was due to a structural manufacturing defect of the DC-DC PCB.
In the area shown below, cracks are observed on soldering of the pins.
The PCB did not have sufficient layer to sustain the weight, and as a result it may crack during transportation.
This is based on data we have collected from the field as this problem consistently shows up on the result of nearly all the reported error 03 cases."

Looks like an admittance of a design and manufacturing defect to me.


After considering what to do about MPP Solar late offer to perhaps fix the two failed inverters I replied :-

Our offer is this :-
1. You refund us for the two inverters we bought - 2520.96 Euros
2. You refund us the 118 Euros charge for the replacement boards that immediately blew up.
3. If you would like these faulty inverters and boards returned then you cover the carriage , otherwise they are going to the recycling centre.
4. I transfer the domain name to you.

We do not believe their sincere apology , no reputable company would leave a client without support for this amount of time.
We have completely lost faith in their Trust Leader level of customer support.


A mere two weeks later we get a response.

I understand you have had a difficult time with these units, so we will do our best to help.

Albert Y certainly is a comedian!

what we will do is that first we will refund you the 80usd postage for the replacement board.

Half-assing customer support , as always!

For another 2 requests , we have submitted to our manager and we will follow-up this issue.

So I guess our issue still hasn't been given to a manager even though I asked for this nine months ago

Later in the day an $83 USD PayPal payment arrived , we have 30 days to accept or refuse the payment.


We decided to refuse the $83 payment , due to previous MPP Solar performance we are unable to trust them.
Reiterating our final offer :-
1. You refund us for the two inverters we bought - 2520.96 Euros
2. You refund us the 118 Euros charge for the replacement boards that immediately blew up.
3. If you would like these faulty inverters and boards returned then you cover the carriage , otherwise they are going to the recycling centre.
4. I transfer the domain name to you.


Enjoy the site statistics from 2018 :-



Our Growatt inverter continues to perform flawlessly while our two MPP Solar inverters rot in their boxes , still failed , still unrepaired.
Still no contact from MPP Solar of course.
I have checked our power usage statistics , since 2018-09-02 we have generated 32% of our power via solar , not bad for a cloudy European winter.
Updated the link to the Growatt inverter site as it was broken after their site update. Apologies.

Purchased Elsewhere

Some nice victim-blaming from Mark Breyer , I'm just happy our misfortune could help you out.

Yes, looks same to me. I decided to buy a Victron Multiplus 5000/70 48v.
I thought about buying from MPP Solar, but this review let me changed my mind.
In Germany we have a saying: "Who buys cheap, buys twice"

Other MPP Solar clients with issues

Easily Bored Engineer

Tracker - MPPSolar - PCM5048 - Time to come out

Happy MPP Solar clients


My MPPSolar inverters have always performed flawlessly.
But then, being an intelligent type, I NEVER EVER run my equipment at more than 80% of it's limit.
Just common sense, I guess.

Some nice victim-blaming and insults from the_unforlorn.
Our MPP Solar inverter also worked 'flawlessly' when running at 40% of its advertised capacity for six months , but couldn't handle the advertised 100% / 5000 Watts for a single day.
Surely the safety margin should be at the manufacturers expense above 100% not the clients below 100% ?
This self-proclaiming intelligent American is happy to pay the 20% premium.
While his inverters are working he hasn't yet experienced the wonderful MPP Solar Support.
Meanwhile our GroWatt 5000 MTL inverter is rated at 5000 Watts and has been working flawlessly for nine months.

Pros vs Cons




Last Updated : 2019-03-02.

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