[RE-wrenches] Warranty Claim Based On Enphase Monitoring Data

[Kent Osterberg]

Matt,

The Enphase and revenue grade meter are in disagreement by less than 
1.1% in the system you are describing - that's good agreement! According 
to the Enphase white paper, the wiring loss in the Enphase cabling 
between the first and 9th inverter is 0.6%. That only applies to the 
last inverter and the average loss for the system will be less, but it 
shows that the ac wiring loss is a significant part of the discrepancy. 
Also, even the revenue grade meter is not perfect - typically ±0.25% 
when new.

Kent Osterberg
Blue Mountain Solar


matt at solar-energy-solutions.com wrote:
> Mark,
>
> We have nine Trina modules on our roof with Enphase.  Enphase says the
> array has produced 2,680 kWh to date.  The revenue grade meter 12 feet
> away says 2,564.  Until I hear otherwise I am reluctant to consider
> Enphase reporting precise.  It seems to be similar to what I would expect
> from a string inverter.  I would be delighted to hear more anecdotes
> confirming your observations.
>
>
> Regards,
>
> Matt
>
>
> Matthew Partymiller
> Solar Energy Solutions LLC
> (859) 312-7456
> matt at solar-energy-solutions.com
>
>
>   
>> Folks,
>>
>> Has anyone used Enphase monitoring data to get warranty replacement on new
>> modules with sub par yield?
>>
>> I have several interesting questions stemming from access to Enphase
>> module
>> level monitoring data.
>>
>> Looking at data from a larger site (80 modules) with no shading issues,
>> instant power production indicates a high degree of uniformity in panel
>> power (Sharp NU-U240F1 and D380) easily within 1%.
>>
>> So what can we now say about the precision and accuracy of this monitoring
>> data? It seems the old school thinking for string inverters was all the
>> monitors were 5% off and reporting 5% more power than actual.
>>
>> Based on the data that I am looking at, it seems the microinverter meters
>> must be fairly precise and possibly fairly accurate as well. Uniformity of
>> module performance must also be fairly high.
>>
>> In any case, this data clearly shows a single module that is not
>> performing
>> as well as it's cohorts. For power levels above 50% of STC, it averages 9%
>> less power than all other modules in the system. So off to Sharp for a
>> warranty replacement? Yes, but, what if I am 5% low on the report from my
>> inverter meter and 5% lower on my power from this one module? What if the
>> module gets back to Sharp and they say it is within spec, now the costs
>> are
>> all mine?
>>
>> Interestingly enough, access to this monitoring data is making more work
>> for
>> me as an installer. With a string inverter, I would monitor power
>> production
>> readings monthly and be happy so long as yields were higher than what I
>> projected when I designed and bid the job. Pretty much fire and forget.
>>
>> Now I am spending time on evaluating this data and doing the work to
>> change
>> out the module under warranty and so forth. I am going to end up putting
>> in
>> quite a few hours into this for what: to recapture 10% of 1/80 of total
>> system yield….0.0013%.
>>
>> I am not complaining, just musing over this interesting evolution.
>>
>> Mark Frye
>> Berkeley Solar Electric Systems
>> 303 Redbud Way
>> Nevada City,  CA 95959
>> (530) 401-8024
>> www.berkeleysolar.com
>>
>>