How accurate are your PV generation figures?

JKenH

I was impressed by some of the generation figures reported on the “talking ‘bout my generation” thread in December. I am curious, however, how accurate some of these figures might be at this time of year. I have noticed this month quite a wide variation between the figures recorded by my inverter app, my generation meter and my Zappi (myenergi) app which uses a CT clamp. 

Yesterday they recorded 5.4, 4.43 and 5.6kWh respectively.
Today they recorded 1.1, 1.31 and 1.4kWh respectively.

Yesterday the highest figure was 28% higher than the lowest. Today, 27% although rounding of such low figures could make almost 10% difference. 

I imagine if the generation meter is tucked away somewhere inconvenient to read the temptation will be to take a reading from an app. I suspect that any readings using CT clamps will be subject to a lot more variation when generation levels are low. Would I be right in assuming that inverter readings will generally record DC generation whereas the generation meter figure will be AC? One would expect the latter to be the most accurate but I would also expect it to be lower than the inverter figure but that was not the case today which does suggest that we should exercise caution when quoting figures for low generation days. 

I also suspect that over the course of a year the total generation figures will be much closer as statistically the errors will even out. 

To date this year the figures I recorded are 5.33 from my inverter app and 5.33MWh from my generation meter. No annual figure is available from the Zappi app.
Last year the figures were 4.71 and 4.78 MWh. Over the year, then, the figures can be accurate but the day to day variations can be significant. 

gefnew

Hi from my install November 2011 till now the inverter reading from sma Bluetooth app and the gen meter is 370Kwh difference after nearly 14 plus years the gen meter the lower amount.

Magnitio

My inverter registers 12582kWh exported since installation. Octopus have paid based on 12636kWh. So a trivial difference (<0.5%). The inverter also records the amount generated by the panels (24996 kWh) separate from the usable energy provided by the inverter (22267 kWh). So loss is about 7% which covers DC to AC conversion plus inverter power consumption, which is not trivial as it is a hybrid inverter running 24/7.

Qyburn

Solaredge. Production overestimate by a bit less than 5%. Import and export underestimate by just over 5%.

ctdctd

SMA Sunny Boy SB2500 inverter been running for 14+ years

Inverter reports 33755kWh generated

Generation meter 341395kWh - this determines my FIT payments  

So, the SMA inverter under reports by about 1.8%

EricMears

ctdctd said:

SMA Sunny Boy SB2500 inverter been running for 14+ years

Inverter reports 33755kWh generated

Generation meter 341395kWh - this determines my FIT payments  

So, the SMA inverter under reports by about 1.8%

Mine's even better !

SB 4000TL-20  Installed  Sept 2011

TGM 50471.7

Inverter 50426

diff 45.7

i.e  Inverter reporting 0.09%  less than TGM

debitcardmayhem

Of course it’s a moot point if all the various meters are out