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SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters

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How reliable are Sofar inverters for an around-8 kW PV installation, and what problems or failures do users report?

Users report mostly acceptable results: one 6.6KTL-X had no problems for over a year, and another 8.8KTL-X owner said a firmware update to v2.20 removed the old clipping around 8 kW and let the inverter reach full peak power [#18112697] [#18662870] [#19158337] The most common problems in the thread were not outright inverter defects but installation/configuration mistakes: too many panels in one string or the wrong input mode caused DC overvoltage errors such as PvOVP, BusOPV or permanent fault, and the cure was to wire the strings correctly and keep each MPPT within its limits [#18322870] [#18323108] [#18359020] [#18360610] [#18699492] Another recurring issue was grid overvoltage: users saw ID01/Grid OVP shutdowns when mains voltage rose to about 253 V, and one case reached 280 V at the customer side; the inverter was behaving as designed in those cases [#18624602] [#18665849] A few users also mentioned Wi‑Fi/software quirks and awkward warranty handling, with the installer, seller, distributor and Sofar service bouncing responsibility between each other [#18306997] [#18322870] [#18323064] [#18331261] [#18772451] There was at least one real hardware failure report, where an 8.8KTL-X tripped AC overcurrent after about a month and then would not restart, so the unit had to go through warranty [#18771167]
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  • #421 19285546
    3301
    Level 34  
    Exactly, it is about the resistance to ground, the cathode, i.e. the positive pole, and we still have pv1 and v2, but these results are completely detached from reality because no matter if I have one or two circuits connected, they are similar, but I can see the difference and some relationship depending on the software version

    Added after 2 [minutes]:

    stev-an wrote:
    This is in the manual and I wanted to do it, but after entering the password we see success and the window closes. The inverter is from November and it seems to be permanently entered 12.

    In point 3. I confirmed the info in item 5 is Poland.

    So I will not change the tension from another country. They block it because after changing the country it enters the Chinese characters - bushes.

    I think no, changing the country in point 4 has never been related to Chinese
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  • #422 19285923
    DEFENCE
    Level 12  
    Oh, I have a constant value of 1554. And have you noticed that when the inverter turns off in History, there are tabs in addition to Generation, History, Grid and Consumption. Unfortunately, it shows 0 in them, it is known that the inverter will not check how much current we have consumed in real time, but why these options appear after turning off the inverter.
  • #423 19285948
    3301
    Level 34  
    If you add a dedicated counter, you could see the consumption and that it shows up after turning it off, I haven't seen it
  • #424 19286037
    stev-an
    Level 19  
    I have one more question for users. How to properly turn off the inverter? There is a way to turn it on in the manual, but I can't read how to turn it off.
  • #425 19286092
    3301
    Level 34  
    Generally, it does not turn off, but if necessary, first AC, i.e. disconnect from the power grid and then the DC switch from the bottom of the inverter
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  • #426 19286406
    stev-an
    Level 19  
    So in reverse order. I do not have a notification and I do not want to incur costs. Thanks.
  • #427 19292674
    Grucha383
    Level 12  
    Does anyone have this soft 2.40 and would post it on the forum?
  • #428 19294186
    marucha79
    Level 15  
    I have a request for clarification on the "Anti Reflux" function. Do I think that setting "Anti Reflux Control" to "enable" and "Reflux Power" to "0 kW" (at least this is what HYD 5000-ES and similar looks like) should completely prevent energy from being pumped into the grid? I suspect that most people use the function for a short time, until installing a bidirectional meter, but maybe someone has experience and is able to confirm how effective this blockade is. Will it not turn out that I am paying for some part of the electricity produced, but it will pass through an ordinary meter towards the network?
  • #429 19294195
    3301
    Level 34  
    Do you have current transformers for this sofarka?
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  • #430 19294278
    marucha79
    Level 15  
    There is a sensor on the clamp for connection with a twisted pair, the instructions show that this should be it.
  • #431 19294329
    3301
    Level 34  
    I did not do it, but if you have sensors, connect it, make settings and check if it limits
    Where did you get these sensors? are there three, one for each phase?
  • #432 19294344
    marucha79
    Level 15  
    This is just a single-phase inverter, so only one sensor was included with the inverter. But it seems to me that while browsing the internet, I saw it somewhere to buy separately. Before I can check anything, it is a bit longer, because the completion of the supporting structure and assembly will take time. And I am asking because I suppose that due to the lack of time for paperwork, the period of "test" use of the installation may be quite long in my case.
  • #433 19296719
    Krzychooo
    Level 16  
    marucha79 wrote:
    This is just a single-phase inverter, so only one sensor was included with the inverter ...

    What are your batteries?
  • #434 19296742
    marucha79
    Level 15  
    No madness - SSB gels, 100Ah so far with plans to expand to 200Ah.
  • #435 19300947
    hermi1
    Level 5  
    prose wrote:
    DEFENCE wrote:
    You immediately had resets or errors on PL. I am asking because I still do not have an inverter connected to the AC grid.

    There were no resets in the morning and in the afternoon, but as we approached noon the tension grew. In my street, there are 4 installations and when they all start to produce energy, the voltage increases and then resets. It's best to set it to DE immediately. And if it is impossible, it remains to connect the transformer lowering the voltage in front of the inverter and then it goes to 253 V.


    Which DE standard do you have set? I have a choice of 3 and I don't know how they differ ?:

    Germany VDR AR-N4105
    Germany BDEW
    Germany VDE 0126
    Moderated By krzysiek7:

    A colleague has already received an answer to his problem in his topic.
    3.1.12. Posting the same or very similar information in multiple forum sections.

  • #436 19302185
    stev-an
    Level 19  
    Users often write about these voltages exceeding 253V. There are already two installations on my line and I often see 254V sometimes 255V on one of the phases and using a three-phase inverter would not make sense. I chose the phase that always holds the norm and connected to it. Sofar3300 has a locked country selection and it would be a problem otherwise. This inverter from the domestic market can be bought cheaply, so I chose it.
  • #437 19302401
    hermi1
    Level 5  
    stev-an wrote:
    Users often write about these voltages exceeding 253V. There are already two installations on my line and I often see 254V sometimes 255V on one of the phases and using a three-phase inverter would not make sense. I chose the phase that always holds the norm and connected to it. Sofar3300 has a locked country selection and it would be a problem otherwise. This inverter from the domestic market can be bought cheaply, so I chose it.


    Well, yes, but then you use energy only on one phase, so a bit weak ... that's not why I bought a 3-phase inverter. I will try to report the matter to the operator and maybe it will be possible to lower the voltage
  • #438 19302772
    stev-an
    Level 19  
    Three single-phase inverters cost PLN 4,600 and with this solution and almost 10kW, one of the neighbors hangs. The tension on the hit was lowered, but after a year they picked up something again.
  • #439 19302823
    Krzychooo
    Level 16  
    hermi1 wrote:
    ... I'll try to report the matter to the operator and maybe the voltage can be lowered


    Good luck.
    Honestly.
    In six months, describe how it was ... 8-)
  • #440 19309554
    waldemarstachowski
    Level 10  
    Hello, please help me

    Sofar Solar 8.8KTL-X FW v.2.30 does not want to cooperate ;) with Tigo
    Current state:
    Two strings of 10 panels each, elevation and azimuth, all types - LR6-60OPH-345M

    Reference PV1 string unshaded (in the analyzed time interval from start to 2:20 pm)
    String PV2 dormer initially covers 5, 4, 3 panels from 11:15 shaded one panel remains until 13:20 (only this panel connected via Tigo)
    Until 5, 4 or 3 panels are shaded, Tigo works sensational, the problem is when the shadow remains only on the last panel from Tigo.
    Already at 10:45 PV1 = 2400 PV2 = 2000
    Until 11:15 PV1 = 2600W PV2 = 2300W
    After 11:15 PV1 = 2600W power drop PV2 = 890W and so selects the maximum power point, i.e. not optimal and it was supposed to be optimal ;) .

    Before connecting the Tigo
    Until 10:45 the maximum power on the PV2 did not exceed 250W with PV1 = 2300
    only in the range of 10:45 to 11:00 PV1 = 2300W step PV2 = 2000W

    Sofar settings:
    Independent PV inputs
    Scanner on every 5 minutes

    Information gained:
    The Sofar Solar headquarters in Poland does not know how to bite it
    Tigo distributor mhh impossible
    Experienced installers admit that there are problems in cooperation between Sofar and Tigo opty.

    Thanks in advance for the suggestions to solve the problem, maybe someone has encountered such a problem

    SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters
  • #441 19309880
    AT PRO
    Level 25  
    waldemarstachowski wrote:

    Sofar settings:
    Independent PV inputs
    Scanner on every 5 minutes


    First, disable scanning completely and see what happens.
  • #442 19316542
    adamac
    Level 12  
    3301 wrote:
    In the initial sofara instructions, the power was shared between the inputs, currently there is no sharing, so all power can be connected to one of the inputs.

    I would like to have your confirmation. I plan to connect 18 panels with the following parameters to 11KTL-X in the near future:
    Open circuit voltage 49.84 volts
    Optimum voltage 42.10 V
    Optimum current 10.69 A.
    Short-circuit current 11.20 A
    Maximum power (theoretical) 450W
    Southwest plain (45 degrees south)
    It would be more optimal in terms of tension to connect them into one string. The power of such a set is 8100W. Will the inverter have problems with this?
    The second issue is the maximum voltage, which in frosts of -25'C can reach 1000V, although the temperatures of the panels themselves will probably not fall so low. I am asking for advice whether to connect 2x9 panels or all in one string.
    Installation with the option of extension on a different slope.
  • #443 19316636
    3301
    Level 34  
    If you take into account the temperature coefficient in the calculations and take the temperature minus 25, the open circuit voltage of the string will exceed 1000 V
    If you are going to expand, now install less by one, but if you want to expand 11ktlx it is 10 kW, so you will add 2-2.5 kW at the most
  • #444 19316690
    adamac
    Level 12  
    Yes, I plan to expand to 10kW as the second building is erected, then I plan to pull 5 panels from this slope and, after buying additional panels, create a second string on the south-eastern slope. If this sofar handles these 18 panels on one chain, then maybe for this time I will connect the panels to 9 pcs and bring 4 wires to the inverter and for the winter I will switch to two strings, and normally all into one in series.
    Would I lose a lot for a year with a combination of 2x9 versus 1x18? Or else, is it better 2x9 or 1x17?
  • #445 19316691
    toolpusher
    Level 23  
    Wouldn't the 8.8 inverter be considered, especially since the panels will be inclined from S about 45 degrees. Additionally, Sofar 8.8 only requires 380V for full power, so with the 12/10 target setting the voltage will be reached.
  • #446 19316767
    AT PRO
    Level 25  
    In the case of a colleague Adamac, you have to consider whether or not to buy other panels. I assume that you will not exceed 10 kW of power in the panels anyway, so a better solution would be to buy 320-340W panels in an amount close to 10 kW. I did not check the price, but I have the impression that it will come out even cheaper and you have a guarantee for the future that you add the same panels in the second string, and believe me, you will not gain anything on these 450W because it is only a panel with larger dimensions. The inverter can become 11 ktl-x because you never know what the weather will be like and it is better to be prepared for super sunny summers.
  • #447 19316991
    adamac
    Level 12  
    Thank you all for the answers. I am aware of the (mis) fit of the kit, so I put this problem on the wallpaper. At the moment, I would simply give up 2-3 panels as soon as possible, and buy some other panels for the other half in the future. Unfortunately, the inverter and panels are here. And for the moment I will have fun with serial connections, and for the winter - parallel connections. I will let you know how Sofar will work below mppt voltages and close to max.
    There is some unknown whether this inverter can work above 6600W on one mppt channel? 3301 are you sure it can work this way now?
  • #448 19317080
    3301
    Level 34  
    adamac wrote:
    Thank you all for the answers. I am aware of the (mis) fit of the kit, so I put this problem on the wallpaper. At the moment, I would simply give up 2-3 panels as soon as possible, and buy some other panels for the other half in the future. Unfortunately, the inverter and panels are here. And for the moment I will have fun with serial connections, and for the winter - parallel connections. I will let you know how Sofar will work below mppt voltages and close to max.
    There is some unknown whether this inverter can work above 6600W on one mppt channel? 3301 are you sure it can work this way now?


    What kind of parallel connection are you talking about? this inverter has a max current of 11A, from the parallel connection it will be 20 so you cannot connect strings in parallel with such modules

    If you divide into two, you have 9x42.1 = 380V and this is not below the nap. mpp and it's good, with one string the voltage is 2x, so also in the mpp range
    On the other hand, in an open circuit, at minus even 20, the voltage may exceed 1000, which is beyond the sofar's capacity
    On one string, you can now connect all the power via DC, I have such installations of 6.12 kW connected to one input at the inverter in one case 6.6 and in the other 8.8 (because it will be an expansion), but give the software version V .....
    I also have 6.12 with two strings of 9 because the planes are a bit different and also do not differ from these two losses if they are within the error
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  • #449 19317363
    marwi123
    Level 13  
    Hello.
    I am going to install installations on a gable roof in the east direction (slightly facing south - azimuth113? ;) . A 42? sloped roof. The installer offers me up to 10kW panels (25x400W) and the Sofar 8.8KTL-X inverter. The installer rejected the other side of the roof due to much lower yields.

    Is the inverter suitable for 10kW? In direct sunlight in the morning, won't the inverter "cut" the maximum output when the panels are not yet warmed up?
    Will it be possible to add any additional, e.g. 2 panels to the above system in the future? Generally, I am focused on maximum yield as I use over 8MWh per year.

    best regards
  • #450 19317366
    adamac
    Level 12  
    3301 wrote:

    What kind of parallel connection are you talking about? this inverter has a max current of 11A, from the parallel connection it will be 20 so you cannot connect strings in parallel with such modules

    Of course, I mean a parallel connection for two mppt.
    3301 wrote:

    If you divide into two, you have 9x42.1 = 380V and this is not below the nap. mpp and it's good, with one string the voltage is 2x, so also in the mpp range
    According to the instructions for 11ktl-x, the mppt voltage range is 480-850V
    3301 wrote:

    On the other hand, in an open circuit, at minus even 20, the voltage may exceed 1000, which is beyond the sofar's capacity
    On one string, you can now connect all the power via DC, I have such installations of 6.12 kW connected to one input at the inverter in one case 6.6 and in the other 8.8 (because it will be an expansion), but give the software version V .....
    I also have 6.12 with two strings of 9 because the planes are a bit different and also do not differ from these two losses if they are within the error

    Thanks for the information. I am also considering the options of connecting these two or three boards to separate microinverters.
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Topic summary

✨ The discussion centers on experiences with Sofar inverters in approximately 8kW photovoltaic (PV) installations, focusing on technical issues, durability, and configuration challenges. Users report generally stable operation with models like Sofar 6.6KTL-X and 5.5KTL-X over extended periods, though some face connectivity problems, especially with Wi-Fi and software availability. A recurring technical problem involves input voltage exceeding the maximum allowed 600V DC for single-phase Sofar inverters (notably the 4KTLM-G2), causing errors such as PVOVP and BusOPV and inverter shutdowns. This is often due to too many PV panels connected in series on a single string, with 15 Q.CELLS Q.PEAK G4.1 305W panels sometimes exceeding voltage limits, especially in cold conditions where voltage rises. Solutions include splitting panels into two strings (e.g., 8 and 7 panels) connected to separate MPPT inputs, though some users report this does not fully resolve the issue. The maximum recommended panels per MPPT input is around 9 to avoid surpassing power and voltage limits. Users also discuss the need for three-phase inverters for larger installations above 7kW on a single phase due to grid operator restrictions. Software and firmware updates are sought after but not easily accessible, with some users lacking Polish language support. Comparisons with other brands like SMA and Fronius highlight Sofar's cost advantage but raise concerns about long-term reliability and service support, which is still developing in some regions. Network-related errors such as Grid OFP (over-frequency) have been reported, with troubleshooting involving network frequency checks and inverter restarts. Overall, Sofar inverters are considered a cost-effective option with some technical caveats related to system design, installation quality, and support infrastructure.
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FAQ

TL;DR: Field owners report 0–20 % daily energy loss when Sofar inverters trip on 253 V grid peaks; “set Country Code 12 for Poland and the problem goes away” [Elektroda, 3301, post #18624621] Why it matters: one menu setting often fixes most unexpected shutdowns without replacing hardware.

Quick Facts

• Max. DC input voltage 1000 V & MPPT window 240-850 V (Sofar 8.8KTL-X manual [Uri, #18921613]) • Recommended DC/AC oversize ratio ≤ 1.2 : 1 for KTL-X models [Elektroda, BikeBarian, post #18360391] • Country Code list: PL = 12, DE = 07, NL = 05 [Elektroda, Defence & 3301, post #18851696] • Typical firmware: V2.30 (increases AC limit from 4.0 kW to 4.4 kW on 4.4KTL-X) [Elektroda, prose, post #19034268] • Service e-mail: service.pl@sofarsolar.com; hotline +48 22 123 98 58 [Elektroda, AT PRO, post #18772451]

How reliable are Sofar inverters in everyday use?

Most 6–9 kW owners report trouble-free work for 1–3 years [Elektroda, iborkim, #18112697; Elekt...

Which menu code should I select for Polish grid parameters?

Use Country Code 12 (PL). It lifts the over-voltage trip to 253 V/10 min and 264 V/1 s, matching Polish NC-RFG limits [Elektroda, 3301, post #18851696] Selecting 07 (DE) raises the limit to 264 V but violates declaration of conformity.

My inverter shows ID01 ‘GridOFP’ and stops at noon—what now?

Measure L-N voltage; if it rises above 253 V, ask the DSO to lower tap settings or move PV to another phase. Until then, temporarily change Country Code to DE (07) or install a 230 → 220 V autotransformer [Elektroda, MariuszFEG, post #18623709]

What causes PvOVP / BusOPV errors on 4KTLM-G2 units?

Voc exceeds 600 V in cold sun. Split the 15-panel string into two of 8 + 7 or use a 3-phase inverter that accepts 1000 V DC [Elektroda, noja102, post #18323557]

Is the MPPT Scan function worth enabling?

Enable only when partial shading occurs; it rescans the IV curve at user-set intervals. Service says it "improves harvest under shade" but reduces output 1–2 % on clean arrays [Elektroda, 3301, post #18622124]

How do I update Sofar firmware myself?

  1. Copy the /firmware folder to the SD card.
  2. Insert card, choose Menu → 5.Software Update, enter password 0715.
  3. Wait until ‘Update DSP1 OK’, ‘DSP2 OK’, ‘FUSE OK’, then reboot [Elektroda, Grucha383, post #19029218]

The display boots for one second at dawn—is that harmful?

No. The capacitors charge when DC rises above 180 V, then discharge if current is < 20 mA; this soft-start repeats without affecting lifespan [Elektroda, rydzyk673, post #19035241]

Why does Solarman show 0.9 A per phase even at 0 W?

Firmware ≤ V2.30 reports reactive standby current as active. Real clamp-meter reading is ~0.2 A; ignore the dash-board figure until a patch arrives [Elektroda, wilk125, post #19038447]

Edge case: can the inverter fail after a breaker trip?

Yes—one 8.8KTL-X died after a 16 A AC breaker opened; display stayed dark despite correct DC voltage, requiring warranty swap [Elektroda, gotycki1, post #18771167]

How to auto-run a 1.5 kW boiler only on surplus PV?

Install a PR-energised relay with the inverter’s CT loop; set closure above 4.5 kW export so the heater engages only in excess production [Elektroda, 3301, post #19053070]
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