Customer convinced that generation meter is not calibrated

[ktech]

Please don't take offence , but how can you fit the gear with out knowing how to use it / set it up .
What inverter is it ?

Eh? Sorry you have completely lost me...

 

[JD6400]

I think once you get into looking at inverters and generation meter readings it becomes another can of worms, i.e. is the inverter reading relating to the DC or AC side, voltdrop issues as well as reactive loads etc..

I am probably wrong , but this post sort of seems to suggest that you have a problem in reading the information from the inverter ?
As i have already said , i am not sure about other inverters but on fronius ones it gives a very easy to understand read out .
Again sorry if i have it wrong , it was not meant to offend .

 

[ktech]

Hi, sorry but you are indeed wrong, no not a problem reading off the inverter. As per original and previous posts issue is with the difference between generation meter and clip on meter monitoring devices, invertor readings never mentioned or implied.

 

[JD6400]

Fair enough , i have had a few tonight .
But please do bear in mind that if the output from inverter matches the generation meter readings , that alone should pacify the customer .

 

[SolarCity]

Although bear in mind that inverter displays can be out too. The only reliable measure of how a system is doing is by looking at the generation meter.

 

[Worcester]

We have 5 different monitoring devices on our various PV generators here.
The Inverters (x3), meters (3 x generation, 2 x import, 1 x export) , immersun and calibrated Solar PV Monitoring System | OpenEnergyMonitor (6 x CT montiors) all tally within about 1%
The two energy monitors, Scottish Power and current Cost have an error factor of between 25% and 50% based on ACTUAL production / consumption.

Speak to them (SP and CC) and they will tell you that they aren't accurate and onlu designed to give the user a guide / base line / indication. The CC version with the pulse meter attachemnt is more accurate.

I VERY much doubt it is the meters at all

 

[FB.]

Although bear in mind that inverter displays can be out too. The only reliable measure of how a system is doing is by looking at the generation meter.

My inverter reads about 0.5% higher than the generation meter. This small difference is probably a result of losses in the few metres of cable from the inverter to the generation meter.

 

[Gavin A]

My inverter reads about 0.5% higher than the generation meter. This small difference is probably a result of losses in the few metres of cable from the inverter to the generation meter.

there's a danger in applying your experience from one system across all inverters.

We were caught out with this assumption a while back, and it turns out that SMA inverters at least don't actually meter the outgoing AC electricity as such, they calculate what it ought to be in watts from the Ampage, and at least on their older models this conversion can be very rough and ready and not actually based on the actual measured grid voltage for some reason - I think it may even be that it's based on measurements of the DC side that are then estimated for the AC side based on some sort of efficiency factor, but I'm not 100% sure. Either way, apparently the SB series output data can be up to 20% out from the actual meter readings, though later models tend to be quite a bit more accurate.

The meter is calibrated, the inverter isn't, and neither are the vast majority of clamp meters, though there are some now that do actually also read the grid voltage and use that to calculate the actual wattage to within around 1% accuracy - Owl ain't one of them though.