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PV Solar consumption monitoring not correlating with Electric Ireland Smart meter readings

  • 03-01-2023 12:55pm
    Registered Users Posts: 89 ✭✭

    Hi i have PV installed since Nov 22. I have a Sofar inverter and have been monitoring my production/consumption with the Solarman PV app. I also am with Electric Ireland Smart meter plan so i get access to the consumption data also. I noticed a significant difference between the Solarman app and the Electric Ireland readings from the smart meter. Firstly I compared the daily kWh figure reported for each day. Note this data does not take into consideration any production power from my solar panels.

    When I looked closer at one day in particular. Below is a plot comparing ESB data versus Solarman data on Dec 31st. ESB data gives kWh data once per hour while Solarman data is reported every 5 mins (in W)

    Looking at this detailed plot for one day, it appears the Solarman and ESB data are tracking each other correctly.

    I converted the Solarman raw data to kWh by multiplying each figure by 5/60 and then adding them all together to give me 24 hour total. Is this correct?

    ESB total = 31.97kWh

    Solarman raw data total = 35.98kWh

    Solarman app consumption figure reported = 25.68kWh (How is this figure so low?????!!!!)

    Again no PV production data is included in any of this.

    Anybody seen something similar? Or can help to diagnose this? Thanks


  • Registered Users Posts: 182 ✭✭curioustony

    I suspect the app is giving you 5 minute samples and not measurements. Makes for pretty graphs, but is not accurate.

    Does the app also provide daily figures? These are more likely measurements.

    If so you can 'unitize' the samples (sum of samples / daily value), and create a pseudo 5 minute measurement for each sample (sample * unitized value). Will be different for each day mind.

    🌞4.55 kWp, azimuth 136°, slope 24°, 5kW, 🛢️10.9kWh, Roscommon

  • Registered Users Posts: 89 ✭✭michaelduignan

    Yeah the app provides a daily kWh figure. but when i compared with the electric ireland smart meter daily figures they are very different. For example on the top graph above these compare daily figures from app vs electric ireland usage daily figures. If you take the first day, the app tells me consumption is ~42kWh while the electric ireland reading is almost 60kWh.

  • Registered Users Posts: 182 ✭✭curioustony

    That's me out. Short of getting a third meter to see which is correct... My assumption would be ESBN

    Maybe somebody with a solarman will have reckognised this.

    🌞4.55 kWp, azimuth 136°, slope 24°, 5kW, 🛢️10.9kWh, Roscommon

  • Registered Users Posts: 2,344 ✭✭✭bullit_dodger

    Your color coding confused me for awhile...... (1st chart blue= solar app, 2nd chart blue = esb)!

    Like curioustony above, I would suspect that the difference is down to the charting interval. The solar app is recording the values every 5 minutes, but what we don't know is if this value that they are recording is

    • the instantaneous value at the exact 5 minute mark
    • the max value within the last five minutes
    • the average of the power over the last 5 minutes.
    • etc

    while the ESB meter, will just add on the value every second I would presume. I would be inclined to believe the ESB meter. They go through some fairly rigorous testing, that said, it's not unheard of to have a dodgy one - although it would be unlikely.

    As a suggestion (probably easier to do this in summer when there are less things going on). Try and turn off as many devices as you can in the house. Plug out TV's/fridges/etc. I guess you'll need to keep the WIFI on for the logging. Basically get down to as close a 0watts as you can. You won't get there, but you might get close. Then plug in for 30 minutes something which you know the current usage of, electric fire, etc. (you can use something like)

    Nevsetpo Power Meter UK Plug Watts Meter Cost Meter Power Monitor with Backlight : DIY & Tools

    and see what both systems report. I'd expect a few watts difference, but they should be pretty much both on the money.

  • Registered Users Posts: 89 ✭✭michaelduignan

    Sorry about the colour coding! I agree it’s unclear how the 5 min interval data is determined. The main thing confusing me though is how they daily figure they provide on the app is calculated. Based on the raw data it is unclear. I emailed SOLARMAN to see if they can answer.

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  • Registered Users Posts: 16 BundE34

    Sorry for the thread revival. but I had solar installed back in Aug with a sofar inverter. I was comparing the figures from the solarman app to the ESB's figures and there seems to be a large discrepancy for the consumption data. The solarman app figures are much lower than the ESB's. I was wondering did the OP ever find a solution? Tia

  • Registered Users Posts: 1 tobine

    I've got same issue solarman app reads 744kwh for 1st to 19th of Jan,smart meter reads 869 from 4th Jan to 19th,that a big difference.

  • Moderators, Sports Moderators Posts: 18,476 Mod ✭✭✭✭slave1

    These inverters read off a CT clamp which will never be as accurate as a meter