Hi Guys

I did two installations for a client over the December holidays, one for him and one for his mother.

Both systems are using the same components: Sofar 6kw inverter, Amass 5Kwh battery and 4 x Jinko 615W bi-facial panels. Cust supplied all components, I just did the labour. While these panels don't face true north, they are probably only a few degrees off of true north and the roof pitch is around 28 to 32 degrees.

On both of these systems the most those panels ever output is 1200w, nowhere near the 2460W they are rated for. I am well aware of losses in cable, heat of the panels etc, but these panels seem to only operate at around 50% of their rated power. Of all the many systems I have installed over the last 9 years, I've never seen any panel perform so badly.

Has anyone else ever experienced this kind of under-performance with a bi-facial Jinko panel?

2 hours ago, Gandalf said:

Hi Guys

I did two installations for a client over the December holidays, one for him and one for his mother.

Both systems are using the same components: Sofar 6kw inverter, Amass 5Kwh battery and 4 x Jinko 615W bi-facial panels. Cust supplied all components, I just did the labour. While these panels don't face true north, they are probably only a few degrees off of true north and the roof pitch is around 28 to 32 degrees.

On both of these systems the most those panels ever output is 1200w, nowhere near the 2460W they are rated for. I am well aware of losses in cable, heat of the panels etc, but these panels seem to only operate at around 50% of their rated power. Of all the many systems I have installed over the last 9 years, I've never seen any panel perform so badly.

Has anyone else ever experienced this kind of under-performance with a bi-facial Jinko panel?

Might want to give the voltages graph a check all the settings?

Might be a bad connection on the mc4 or something like that.

2 hours ago, Gandalf said:

Hi Guys

I did two installations for a client over the December holidays, one for him and one for his mother.

Both systems are using the same components: Sofar 6kw inverter, Amass 5Kwh battery and 4 x Jinko 615W bi-facial panels. Cust supplied all components, I just did the labour. While these panels don't face true north, they are probably only a few degrees off of true north and the roof pitch is around 28 to 32 degrees.

On both of these systems the most those panels ever output is 1200w, nowhere near the 2460W they are rated for. I am well aware of losses in cable, heat of the panels etc, but these panels seem to only operate at around 50% of their rated power. Of all the many systems I have installed over the last 9 years, I've never seen any panel perform so badly.

Has anyone else ever experienced this kind of under-performance with a bi-facial Jinko panel?

My panels face south west with a 10 degree tilt in that direction. In winter I get about 450W out of my Bifacial 650W panels, between September and March I pretty much get the full power rating from them so I doubt the angle has anything to do with it.

What are the specs of the inverter? Maybe its clipping the power.

1 hour ago, Denns said:

My panels face south west with a 10 degree tilt in that direction.

Which hemisphere do you live in?

1 minute ago, Bobster. said:

Which hemisphere do you live in?

South Africa. If you are questioning the angle its because the garage roofs are angled that way lol. So all my 12 panels are mounted on the garage roofs.

Far cheaper to just install on the roof and add more panels than trying to build or get the mounts to angle them properly. I still have the whole house roof available with no trees shading any part of the roofing so I can easily expand to about 20kWp of panels when or if my power requirements go up considerably. Especially with me not having a grid connection to the inverter and also getting my house electricity supply removed by Citipower.

Thanks @Denns . I do see some south facing panels in my neck of the woods, and I have seen that my ENE facing string can produce useful power up to about 15:00, maybe a bit later in summer.

3 hours ago, Stefan Cornelissen said:

Might want to give the voltages graph a check all the settings?

Might be a bad connection on the mc4 or something like that.

VOC was around 196V when I tested. A bit low for my liking, but this is what the customer supplied.

I doubt it is a bad crimp on the MC4 because both sites are the same in terms of production, roughly 300W per panel.

3 hours ago, Denns said:

My panels face south west with a 10 degree tilt in that direction. In winter I get about 450W out of my Bifacial 650W panels, between September and March I pretty much get the full power rating from them so I doubt the angle has anything to do with it.

What are the specs of the inverter? Maybe its clipping the power.

Sofar HYD 6K-EP inverter with CAN communication established. I suspect there may be clipping.

Perhaps I should try remove communication and program the charge settings manually.

17 minutes ago, Gandalf said:

Sofar HYD 6K-EP inverter with CAN communication established. I suspect there may be clipping.

Perhaps I should try remove communication and program the charge settings manually.

Off the top of my head, maybe there is setting that is clipping the power. I see the panels are way below the specs of the inverter.

Maybe try running a load higher than 2kW and in full sun to see if the power changes? I assumed on my inverter I was capped to 2.4kW. But it was because I never tried running a higher load. I ran a load of 3.2kW and along with the power used for charging the batteries, managed to hit 3.95kW which is at the limit of my inverter Max PV power of 4kW.

Are the panels really 615W (dumb question but you never know).

Same thing here, the highest daily is 1900W but if its cloudy and temperatures drop then when the sun appears, it goes to 2500W but for few minutes like 10-15min then drops back to 1900W. Tried running high consumptions but the PV remains 1900W. 🤷‍♂️

Edited January 13Jan 13 by Thulane

17 hours ago, Denns said:

Off the top of my head, maybe there is setting that is clipping the power. I see the panels are way below the specs of the inverter.

Maybe try running a load higher than 2kW and in full sun to see if the power changes? I assumed on my inverter I was capped to 2.4kW. But it was because I never tried running a higher load. I ran a load of 3.2kW and along with the power used for charging the batteries, managed to hit 3.95kW which is at the limit of my inverter Max PV power of 4kW.

Are the panels really 615W (dumb question but you never know).

You make a good point about adding a heavy load to see how much power is drawn, I will try that this weekend.

As for the panels themselves, the sticker says 615W and it is a big heavy panel, but the figures printed on the sticker could be an exaggeration. The funny thing is the IMP on the sticker is 13.46A, but I have never seen more than 7.08A being drawn. Once again this could be because of small loads not pulling enough juice from the panels.

I will do some more tests and report back...

On 2026/01/12 at 10:09 AM, Gandalf said:

While these panels don't face true north, they are probably only a few degrees off of true north and the roof pitch is around 28 to 32 degrees.

20 hours ago, Denns said:

Are the panels really 615W (dumb question but you never know).

Maybe another dumb question, but how did you install the panels? Flat close to the roof? How much light is falling on the rear face of the panel? What's the bi-facial factor spec of this panel?

21 minutes ago, GreenFields said:

Maybe another dumb question, but how did you install the panels? Flat close to the roof? How much light is falling on the rear face of the panel? What's the bi-facial factor spec of this panel?

Typically Bifacial is some 10% more than what the rated output is. So 615W would be some 680W with good irradiation on both sides. Even if the 615W includes the rear, he should still be seeing about 80% of the rating rather than the 50% at the moment. So without the rear it would be some 550W.

18 hours ago, GreenFields said:

Maybe another dumb question, but how did you install the panels? Flat close to the roof? How much light is falling on the rear face of the panel? What's the bi-facial factor spec of this panel?

Panels are on rails attached to roof hooks, roughly 65mm off the tile. I don't think there is any light falling on the rear of the panels. I have no idea about the bi-facial factor of the panel, I just fitted what the customer bought. I will find out more...

18 hours ago, Denns said:

Typically Bifacial is some 10% more than what the rated output is. So 615W would be some 680W with good irradiation on both sides. Even if the 615W includes the rear, he should still be seeing about 80% of the rating rather than the 50% at the moment. So without the rear it would be some 550W.

I totally agree with you and this is what I was expecting to see, but in this setup they peak at 300w per panel. I thin it might be something in the settings of the inverter. Sadly the settings are rather basic compared to the usual Sunsunk or Deye inverters I am used to.

7 minutes ago, Gandalf said:

I totally agree with you and this is what I was expecting to see, but in this setup they peak at 300w per panel. I thin it might be something in the settings of the inverter. Sadly the settings are rather basic compared to the usual Sunsunk or Deye inverters I am used to.

I found the datasheet for those panels and it doesnt look good. The STC value is 615W. But the NOCT value is only 463W for those panels. So in real world conditions you would only be seeing about 1850W. I might be mistaken but it is very rare for panels to hit the STC value. NOCT is at 20 degrees with 1m/s wind and 800W/m2 irradiance. In our current climate in SA those panels would be way over the 20 degrees so the power output would be further reduced.

I would check based on the mounting angle at what time the panels are expected to produce max power relative to the sun angle. Then if the skies are clear, run a load higher than 3kW and see what you pull from the panels.

Edited January 14Jan 14 by Denns

4 minutes ago, Denns said:

I found the datasheet for those panels and it doesnt look good. The STC value is 615W. But the NOCT value is only 463W for those panels. So in real world conditions you would only be seeing about 1850W. I might be mistaken but it is very rare for panels to hit the STC value. NOCT is at 20 degrees with 1m/s wind and 800W/m2 irradiance. In our current climate in SA those panels would be way over the 20 degrees so the power output would be further reduced.

I would check based on the mounting angle at what time the panels are expected to produce max power relative to the sun angle. Then if the skies are clear, run a load higher than 3kW and see what you pull from the panels.

This is for my one panel on the Victron charge controller. But I do get the full wattage of the panel. I have seen over 580W a few times despite my SW 10 degree orientation. And as expected, because it is bifacial, if it had irradiance at the back, it would be 670W. Mine doesnt have a NOCT rating though. So technically you should still be seeing the 615W. The NOCT rating might not matter as much if this panel of mine and the 650W panels on my inverter are almost always hitting their full power. My 650W are also bifacial and they are Fivestar panels.

Edited January 14Jan 14 by Denns

On 2026/01/12 at 10:09 AM, Gandalf said:

Hi Guys

I did two installations for a client over the December holidays, one for him and one for his mother.

Both systems are using the same components: Sofar 6kw inverter, Amass 5Kwh battery and 4 x Jinko 615W bi-facial panels. Cust supplied all components, I just did the labour. While these panels don't face true north, they are probably only a few degrees off of true north and the roof pitch is around 28 to 32 degrees.

On both of these systems the most those panels ever output is 1200w, nowhere near the 2460W they are rated for. I am well aware of losses in cable, heat of the panels etc, but these panels seem to only operate at around 50% of their rated power. Of all the many systems I have installed over the last 9 years, I've never seen any panel perform so badly.

Has anyone else ever experienced this kind of under-performance with a bi-facial Jinko panel

I would verify the authenticity panels with Jinko directly, they should have a serial number verification process to check the panels are genuine.

Once that's confirmed, it's probably the inverter that's causing the limit due to the settings / setup.

You should get near the full power rating of the panels on a good day, not 50%. Bifacial rating would be over and above the 615w, so that doesn't change anything. Noct as per specsheet is normal. On a bright summers day, production will be more than that.

Edited January 14Jan 14 by abd7

On 2026/01/14 at 8:36 AM, Denns said:

I found the datasheet for those panels and it doesnt look good. The STC value is 615W. But the NOCT value is only 463W for those panels. So in real world conditions you would only be seeing about 1850W. I might be mistaken but it is very rare for panels to hit the STC value. NOCT is at 20 degrees with 1m/s wind and 800W/m2 irradiance. In our current climate in SA those panels would be way over the 20 degrees so the power output would be further reduced.

I would check based on the mounting angle at what time the panels are expected to produce max power relative to the sun angle. Then if the skies are clear, run a load higher than 3kW and see what you pull from the panels.

These NOCT specs of 463W along with temp losses are more consistent with what I am seeing. I think these panels are sub-par.

I am not really worried about it because I didn't supply them. I was just curious as to why these fancy new panels produce the same power as my 6 year old 330W panels.

Jinko panels (genuine ones) are tier 1 and perform just as well as any other brand.

We have the Jinko 615w producing full 615w power without any issues on other sites.

Forgive my ignorance but it would also answer a question of mine.

Could it have anything to do with the battery brand which has a .5 C rating?

43 minutes ago, Rory Kilpatrick said:

Forgive my ignorance but it would also answer a question of mine.

Could it have anything to do with the battery brand which has a .5 C rating?

The 0.5C battery if set correctly in the inverter settings prevent sending more than about 45A - 2 5kW to the battery. When loads are also connected the panels could generate more to cover the load as well. Above value determined by the PV that panels can generate. Inverter/BMS will control the maximum as per inverter setting and BMS firmware.

7 hours ago, Rory Kilpatrick said:

Forgive my ignorance but it would also answer a question of mine.

Could it have anything to do with the battery brand which has a .5 C rating?

This has been my thinking for a few days now. Maybe the battery is telling the inverter via CAN-BUS to not charge any higher. I will be visiting the site tomorrow and plan to unplug the communication cable and set the battery to lead-acid to see what happens.

1 hour ago, Gandalf said:

This has been my thinking for a few days now. Maybe the battery is telling the inverter via CAN-BUS to not charge any higher. I will be visiting the site tomorrow and plan to unplug the communication cable and set the battery to lead-acid to see what happens.

As @Scorp007 said, when a load is connected, you should be seeing much more. Even at 50A charging you should see the full power of the panels.

On 2026/01/16 at 4:46 PM, Denns said:

As @Scorp007 said, when a load is connected, you should be seeing much more. Even at 50A charging you should see the full power of the panels.

I was on site this Saturday and did a test. It was around 13:30 and the battery was at 81% SOC. I turned on a few items getting the load up to 5.1Kw. The solar maxed out at 1.3Kw (325W from each 615W panel). I checked the crimping of the MC4's and also checked if the DC breaker connections were tight. I tried different battery settings and user settings, but the solar production stayed the same.

Looking at your previous post stating the NOCT output of this panel, factoring in the temperature of the panels at midday as well as losses over 30M of 6mm PV cable, maybe this is correct...