I’ve had my emonPI a few weeks as an upgrade from an older solution that couldn’t monitor usage/solar at the same time: Accuracy of existing CT clamps since adding PV install - do I need an Emon solution? - #4 by Greebo
I had my own Pi2, so I bought the kit and put it together.
I’ve seen the voltage reading show between 227 and 233 at random times of the day, so the supplied VMRS AC-AC adaptor seems to be doing its job?
The whole emonPi seems to be working well and i’m getting clear and distinct values for usage and generation, but i’m not convinced the results are accurate for two reasons.
Usage doesn’t match the months of figures and trends I had on the old system. For example, baseline usage through the night on the old monitoring system at 4:30am was always around 170w. With EmonPi that figure is around 120w. This is a common trend when monitoring usage, everything through the day seems much lower than recorded with the previous system.
Generation is always lower than the Generation Meter and the Solar Edge inverter numbers. Here are daily totals from my Generation Meter, the Solar Edge app and from EmonCMS.
20th Oct, Gen Meter (8.4), Solar Edge (8.6), EmonCMS (7.9) - diff between Gen.Meter/Emon - 6.0%
21st Oct, Gen Meter (10.9), Solar Edge (11.2), EmonCMS (10.2) - diff between Gen.Meter/Emon - 6.4%
22nd Oct, Gen Meter (15.6), Solar Edge (16.1), EmonCMS (14.5) - diff between Gen.Meter/Emon -7.0%
23rd Oct, Gen Meter (11.0), Solar Edge (11.3), EmonCMS (10.2) - diff between Gen.Meter/Emon - 7.3%
24th Oct, Gen Meter (14.9), Solar Edge (15.4), EmonCMS (13.9) - diff between Gen.Meter/Emon - 6.7%
From reading various forums i’ve seen that Solar Edge can always report a little high, but even using the Generation Meter the figures to compare against the ones out of EmonCMS they consistently 6 or 7% out, and always lower.
But when I compare the old 170w baseline low to EmonCMS low of 120, that’s almost 30% difference. Appreciate there will be some variability, but that seems too much?
Even staring at the inteverter and emonCMS at the same time looking at live generation, it always shows lower readings in emonCMS compared to the inverter.
So my question, do I need to calibrate? if so, what is the best way with what I have available?
I have one of these plug in energy monitors.
I can’t vouch for its pure accuracy but maybe it could help? That webpage suggests +/- 2%?
I also have a basic mulit-meter, but having read the learn calibration article I still am no wiser what to do with it safely? Being honest, i’m not sure what setting to choose or where to place it?
I suppose I should be looking at the accuracy of generation and consumption in isolation?
I’m not sure what more I can do with regard generation? The figures are already there. Could I amend the config file to up generation by 6.5%
I could then attempt to calibrate the generation using a kettle/heater or something? Check the energy reported from the plug in meter I have versus the kettle/heater attached to the CT clamp on the emonPi? Like this?
Then amend the figures is required from there?
Although still not quite sure what extra or how i’d get extra data from the multi-meter?
Would it be better to calibrate voltage first? (if so, how?) Before heading into amending anything from steps 1 and 2? ie amending the voltage setting will skew both consumption and generation figures?
Any help, advice or thoughts would be very much appreciated.