Tigo versus inverter power discrepancy

[mciholas]

I've recently put into operation an array of 30 Canadian Solar CS6R-395MS-HL panels with Tigo TS4-A-O optimizers connected to an Amensolar N3H-X10-US (aka NHX-10K).

At peak power today, the Tigo was reporting 10385 watts of PV output:



About 87% of panel nameplate rating.

The inverter was reporting 9630 watts, 81% of nameplate rating, and about 7% less than the Tigo reported value. The Tigo consistently reports more power than the inverter at other times as well.

The inverter also reports power per MPPT (they add up to 9630 watts), and reports voltage and current for each MPPT (which also computes out to near 9630 watts). So the inverter numbers are self consistent at least.

The Tigo system doesn't seem to let me dig down to the volts/amps level on each panel, only giving me the power per panel, so nothing there to check.

When you look at the energy, the KWH produced, The inverter said yesterday I had 65.4 KWH produced by the PV array, Tigo says 70.2 KWH, which matches the power error exactly.

7% error seems like a lot for decent electronics, more than one would reasonably expect. My tendency is to believe the inverter, but Tigo has a good reputation for making quality stuff.

So who is right? Why is one of them wrong?

Mike C.

 

[Quattrohead]

I would be inclined to believe the Tigo over the inverter. Time to crack out the DC clamp meter.

 

[zanydroid]

I was inclined to believe the inverter b/c it has more room for hardware and software to do the measurement than an MLPE... but then i thought, will the extra readings from the 30 Tigos help to average out the error.

Another thought is, does the inverter guesstimate the efficiency (if the error is always the same, it could be some fixed scaling factor in the software), or do something that measures the efficiency end to end, like integrate the output voltage and current exiting the MPPT.

 

[mciholas]

I was inclined to believe the inverter b/c it has more room for hardware and software to do the measurement than an MLPE... but then i thought, will the extra readings from the 30 Tigos help to average out the error.

As you can see from the array display, the Tigos agree on power very closely. They certainly won't level out a 7% error.

Another thought is, does the inverter guesstimate the efficiency (if the error is always the same, it could be some fixed scaling factor in the software), or do something that measures the efficiency end to end, like integrate the output voltage and current exiting the MPPT.

I thought about that, too, like the inverter is telling me the effective power of the array after AC conversion.

But the inverter is also reporting MPPT voltage and current, which one would not think would be similarly adjusted, and those compute out to the array power the inverter is reporting. So I think this is really the array power without any efficiency calculation, which makes the most sense.

When I look at the load, grid, and PV power, the inverter numbers seem to match up better. Of course, all those numbers are coming from the inverter.

Today, Tigos said 69.2 KWH produced, inverter says 64.5 KWH, right at 7% off.

My main concern here is not the accuracy per se, although that would be nice, but to make sure this isn't an indicator of some issue in the system that needs to be addressed.

Mike C.

 

[Solar Guppy]

What is the length of the DC wire runs? You will have IR losses, I could see a percentage or two with this.

Then there is Tigo reports input power, not output power and that is likely where most of the difference in reporting ( AI Gemini )

 

[mciholas]

What is the length of the DC wire runs? You will have IR losses, I could see a percentage or two with this.

Very short. Longest one is about 50 ft. That means the worst string is suffering about 0.1 ohm total round trip resistance, or about 1 volt drop. Maybe this is 2 volts with the panel leads. That's nowhere near the 7% indicated (it is about 0.7% loss). That would be about 700 watts of lost power in the wires which would be enough to fry them.

Then there is Tigo reports input power, not output power and that is likely where most of the difference in reporting ( AI Gemini )

So I have 700 watts being wasted by the Tigo optimizers? That's 23 watts per unit, they will be super hot! I really can't believe that is the case.

That would also mean my array would be more productive without them. I ended up with TS4-A-O optimizers (monitor + shutdown + optimize) due to getting a deal on them that made them the same price as the TS4-A-S (monitor + shutdown) which I was planning to use initially. Maybe I made a mistake since the array really doesn't need optimizers.

Mike C.

 

[Solar Guppy]

So I have 700 watts being wasted by the Tigo optimizers? That's 23 watts per unit, they will be super hot! I really can't believe that is the case.

All electronics have losses, even the best have 2-3% losses typically and its not a linear function.

Then there is precision of the measurement components. Typically consumer devices are 5% at best and current measurement requires high sensitivity which is significantly more cost for the op-amps with the small currents involved. I got huge pushback on the products I designed which was to 1%.

Then there is "make in buyer / owner happy" by reporting better performance than actual and unless you have measurements at multiple points one would never know. The manufacture like to boast how much they improve performance and is worth the cost.

As to harvest from solar arrays without?

Of course solar should be more productive without secondary devices inline, right there they have to improve 2-3% just to break even in energy and likely a payback of never in more energy generated.

 

[kburndred]

I recently added 48 Tigo's to my system (2 X 18KPV, 48 X 460W PV Modules, ESS 80kWh)
I find the Tigo's are extremely unreliable. The output displayed from Tigo NEVER matches what the inverters report. Most of the time I see more power reported by my inverters than Tigo.
Tigo monitoring web page is terrible, the system view NEVER matches the other pages and does not dynamically update.
I was expecting great things from Tigo but instead I have nothing but trouble and simply can't trust ANYTHING that is reported.
I wish I could shit-can the Tigo's, but Fire Safety code forces me to have RSD.
Everyday different issues, modules not reporting, not connecting, always different PV modules each day.
I added 5 TAP's as requested but still having massive issues.
I am sick and tired of the B.S.
Is anyone else having massive problems with Tigo?
Tigo wants me to troubleshoot their system, removing each Tigo and measuring voltages etc. Seems like B.S. because from one day to the next it's different Tigo's not working.

 

[Oldphile]

Is anyone else having massive problems with Tigo?

I did. Starting around July I had open tickets with TIGO for zero reporting. The CCA wasn't reporting to the TIGO cloud. At one point they suggested replacing the CCA, but that never happened. This went on for months then magically the CCA started reporting. My system is small, only 17 optimizers and one TAP. At one point they were questioning and blaming how I implemented RSD activation. That made no sense as my PV panels were producing, just not reporting.

 

[grhopper]

I am having the same issue. I have 34 panels in 5 arrays. 4 arrays have 7 panels and the other has 6. Sol-Ark 15k inverter with 3 MPPTs. 2 strings each on MPPT 1 & 2 with the final string on MPPT 3. I don't know which array is connected to which MPPT. I tried comparing the Tigo numbers to the Sol-Ark numbers, but wasn't able to match it up 100%.

Tigo reports 1,110kWh produce in January, Sol-Ark reports 992kWh. Am I really losing 10% of my production in the transfer?

 

[Solar Guppy]

Tigo reports 1,110kWh produce in January, Sol-Ark reports 992kWh. Am I really losing 10% of my production in the transfer?

Tigo just likes to report feel good values, its not reality and never has been

 

[Oldphile]

The Tigo system doesn't seem to let me dig down to the volts/amps level on each panel, only giving me the power per panel, so nothing there to check.

You can see voltage and current if you pay for premium monitoring. You can activate this feature temporarily as a trial version. It measures voltage and current into the TIGO optimizer. I didn't find it useful.

 

[mciholas]

You can see voltage and current if you pay for premium monitoring. You can activate this feature temporarily as a trial version. It measures voltage and current into the TIGO optimizer. I didn't find it useful.

Me, neither (there is a 1 month free trial).

In fact, I find nothing about the Tigo optimizers useful. I wish we didn't have them.

I also suffer the Tigos reporting 10% more energy than the inverter thinks it got. Guess that's a built in "feature".

Mike C.

 

[TechRider]

I was curious to see how off my system was.

54 panels to a Sol-Ark 15k. So far today...
Solar Assistant: 5.8kWh
Tigo: 5.48kWh

I wanted the optimizers because I have sort of a non-standard panel layout for some of the panels and some shading issues with some trees. I started with them so I can't say how much they've helped but if I believe their reporting on "not good" days, it's up to 10% more.

 

[kburndred]

Well it's clear to me that sometimes the Tigo optimisers don't connect, sometimes not all PV Modules connect and other times they all do. Throughout all this the numbers reported by Tigo always differ from the inverter. This is partly Tigo's reporting architecture which has a very slow push interval. It's roughly every 4-10 minutes, whereas my inverter pushes data every 45s. This creates a lot of discrepency. I even created my own reporting/dashboarding system and combined data from my 18KPV inverters and Tigo modules on one dashboard. This really highlights the differences. Unfortunatley there's nothing that can be done to alter the Tigo data push interval. I can post some screenshots if anyone is interested.

 

[Oldphile]

This is partly Tigo's reporting architecture which has a very slow push interval. It's roughly every 4-10 minutes

TIGO's report more frequently. The free monitoring shows 15 minute data. The premium monitoring shows 1 minute data. If you upgrade to premium you will see 1 minute data in the past as well as going forward.

 

[kburndred]

Yes I get what you're saying and you are right, however, Tigo pushes a batch of data every 4-10 minutes. When you look at the Tigo "Dashboard" it can be as much as 10 minutes old. If you place the EG4 monitor screen side-by-side it's impossible to compare anything. There is a brief period of about 1 minute if EG4 and Tigo just happen to update at the same time when you can get a reasonable comparison.

 

[Dustyx2]

Made me curious so I went back over 3 months of reporting and Tigo was showing slightly more than 1% more production than the Sol-Ark15K.
That's 24 optimizers and 1 Tap. Best "reclaimed energy" day was 48% on partially snow covered panels. Only issue I've had is the famous Tigo/ Sol-Ark arc faults. May have that figured out. Time will tell.