Field inverter efficiency vs CEC/Euro spec

[nerdralph]

At around 90% capacity, I'm seeing about 95.7% efficiency from Solis 1P-6K-4G-US inverters, vs 97.5% spec.
For the Growatt 6000TL-XH-US, I'm seeing about 94%, vs 97% spec.
For the KStar 5000D and 6000D, I'm seeing only 90% vs 97.9% spec. I've asked for independent test results confirming their 97.9% Euro efficiency spec, but doubt they exist.

I'm curious to see how SMA and Fronius compare. I've got numbers from a couple old Fronius Galvo inverters, but haven't used the Primo series.

[Mike 134]

How are you determining your efficiencies? Measuring DC volts and amps in, and AC volts and amps out with quality meters?

[nerdralph]

How are you determining your efficiencies? Measuring DC volts and amps in, and AC volts and amps out with quality meters?

I'm using the inverter PV input power and grid output power MODBUS data. With the KStar efficiency being so low, I checked the current voltage with a couple meters. The current measurements are only good for +/- 2%, but I think the voltage measurements are an order of magnitude more accurate, as I've calibrated with a precision voltage reference.

Anyone with a data logger on their Sunny Boy inverter should be able to see the input and output power in order to calculate the efficiency. Same goes for a Fronius inverter with the data manager card.

[nerdralph]

I remembered I downloaded the 2021 CEC grid-tied inverter list, and took a look at the 6 kW inverters. The Solis 1P6K-4G-US is #1 for efficiency:

weighted efficiency vmin/vnom/vmax, vnom: 97.05 / 97.32 / 97.45, 380 Vdc

The Sunny Boy 6.0-US-40 isn't far behind: 96.43 / 97.27 / 97.05 365 Vdc

I can think of a couple reasons why I'm seeing the efficiency of the Solis 1P6K-4G-US below the range of values in the CEC database:
1) I doubt the unit that underwent testing was a random sample from the production line.
2) It looks like the testing is done with three strings at equal power. My configuration is 2 strings, with 1 string input unused.

I've searched for an equivalent Euro efficiency certification database, and can't find one. So maybe some inverter manufacturers just do their own testing rather than getting an independent lab like Intertek.

[nerdralph]

Here's my review of the KSTAR inverters, including a bit of monitoring data:

http://nerdralph.blogspot.com/2023/04/kstar-single-phase-string-inverters.html

Given the results, I wouldn't recommend KSTAR Blue-G single-phase inverters.

[Ampster]

.........

Given the results, I wouldn't recommend KSTAR Blue-G single-phase inverters.

Since they are not compliant with UL 1741 I would not recomentd them either for grid interacive use since they would not likely be approved by a utility. . They are also not UL listed for off grid so they probably would not pass a building inspection anyway.

In the larger picture, with the cost of solar panels being so inexpensive, my priorities are features before I care about efficiency. I can always add another solar panel to make up the loss from ineffciency but having a feature that allows me to optimize my return in the changing NEM environment in California is priceless.

[nerdralph]

Since they are not compliant with UL 1741

As far as I can tell, they are UL 1741 compliant, but they aren't UL certified and listed. I agree their use probably wouldn't be officially approved by a utility, but given how many electrical code violations I've seen on PV systems that passed inspection, I think many inspectors wouldn't notice that UL 1741 isn't on the label.

[SunEagle]

As far as I can tell, they are UL 1741 compliant, but they aren't UL certified and listed. I agree their use probably wouldn't be officially approved by a utility, but given how many electrical code violations I've seen on PV systems that passed inspection, I think many inspectors wouldn't notice that UL 1741 isn't on the label.

If you don't use quality UL listed equipment you run the risk of a fire and your Insurance company not coving your home. That is a gamble you have to decide on but if someone is hurt then you will probably be arrested.

[Ampster]

As far as I can tell, they are UL 1741 compliant, but they aren't UL certified and listed. I agree their use probably wouldn't be officially approved by a utility, but given how many electrical code violations I've seen on PV systems that passed inspection, I think many inspectors wouldn't notice that UL 1741 isn't on the label.

Technically the inspector does not care abut UL1741 since that is a standard for interoperabilty with the utility. Howeve you state in your linked review that they are not certified to UL1741 so how could they be compliant with UL174 if UL has not tested them? The inspector is going to care about a UL listing because that is in the building code. It should be noted that UL listing is the operative term not certified. Presumably the buildig permit requires listing the equipment in the permits and the dodes typically require listed equipment. No doubt there there are many examples of violations but that is not the standard to which we would hope people are held to.
I do agree with your review that does not recommend them, but for different reasons. I don;t think efficiency is as important in a device which uses a free fuel as other features or complianc issues.