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Solar installed then consumption apparently increased by ~60kw per month

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petalouthi
petalouthi Posts: 18 Forumite
10 Posts Photogenic
We had Q-Cells solar panels/inverter/battery installed in Nov 23. The meter wasn't changed as already suitable.

We have taken our own monthly meter readings for many years, so have accurate consumption figures prior to installation.

Our lifestyle/pattern of absences from home/use of appliances didn't change when solar installed.

According to QCells app, our consumption has increased by a fairly consistent roughly 60kw per month from the month of installation. (As our annual consumption before installation was around 2600kw/year, an extra 720kw/year is quite significant.)

We set the inverter to charge from the grid during cheap period during the night for the winter months, but turned this off in the summer. The extra consumption appeared to remain at around 60kw under both regimes.

I don't think the CT clamp is on the wrong way round, as the system works in general as it should - more generation, more export on sunny days and in summer, more import in winter and when inverter set to import at night.

I think the app must calculate consumption as
consumption=import+generation-export
rather than directly measure it in some way. Is this the case?

Import and Export figures on the app match those on the smartmeter very well.

I can think of a couple of explanations for the apparent extra consumption:
1. The inverter is using a lot of power itself. Qcells told us that it should be using about 10w/hour. To account for the problem it must be using more than 80w/hour.

2. Generation is being over-recorded. This would result in consumption looking higher than it actually was.

Can anyone help?

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Comments

  • QrizB
    QrizB Posts: 18,245 Forumite
    10,000 Posts Fourth Anniversary Photogenic Name Dropper
    Current clamps aren't particularly accurate.
    You should have a generation meter as well as your import/export smart meter. How does the generation meter compare to the generation totals in the app?
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Vodafone BB / iD mobile. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 34 MWh generated, long-term average 2.6 Os.
    Not exactly back from my break, but dipping in and out of the forum.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs, Best kettle!
  • tim_p
    tim_p Posts: 877 Forumite
    Eighth Anniversary 500 Posts Name Dropper
    Has your annual consumption actually increased by the 720kWh?
  • matt_drummer
    matt_drummer Posts: 2,009 Forumite
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    Battery charging and discharging losses probably account for a lot of it.

    If you are charging from the grid at night and then using batteries when the sun isn't shining you will consume more electricity than if you just took it from the grid as you used it.
  • wrf12345
    wrf12345 Posts: 881 Forumite
    Sixth Anniversary 500 Posts
    You need to look at daily consumption, see if turning everything off except for solar results in the high usage, 2kw a day is roughly 80W an hour, which could be that inverter and associated electronics permanently on. I had relatively simple solar/inverter system more than ten years ago and never had any kind of excess consumption even in winter but with more powerful modern systems and their constant monitoring and battery electronics who knows?
  • Gerry1
    Gerry1 Posts: 10,848 Forumite
    Part of the Furniture 10,000 Posts Name Dropper
    wrf12345 said:
    You need to look at daily consumption, see if turning everything off except for solar results in the high usage, 2kw a day is roughly 80W an hour, which could be that inverter and associated electronics permanently on. I had relatively simple solar/inverter system more than ten years ago and never had any kind of excess consumption even in winter but with more powerful modern systems and their constant monitoring and battery electronics who knows?
    Nope, those units make no sense.  2kWh per day is roughly 80W continuous.
    FTFY !
  • jimjames
    jimjames Posts: 18,664 Forumite
    Part of the Furniture 10,000 Posts Photogenic Name Dropper
    What does your actual electricity meter show? If that isn't increased by 60kWh a month then it's the app giving erroneous data
    Remember the saying: if it looks too good to be true it almost certainly is.
  • QrizB
    QrizB Posts: 18,245 Forumite
    10,000 Posts Fourth Anniversary Photogenic Name Dropper
    jimjames said:
    What does your actual electricity meter show? If that isn't increased by 60kWh a month then it's the app giving erroneous data
    So I read it as "I know my import and export, but my app thinks my household's consumption has increased by 60kWh a month".
    Reading the import meter won't directly help with that.
    However, assuming OP has a generation meter, they can check:
    Consumption = Import - Export + Generation.
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Vodafone BB / iD mobile. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 34 MWh generated, long-term average 2.6 Os.
    Not exactly back from my break, but dipping in and out of the forum.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs, Best kettle!
  • Scot_39
    Scot_39 Posts: 3,501 Forumite
    Ninth Anniversary 1,000 Posts Name Dropper
    edited 20 January at 3:53PM
    Anything you feed into a battery - you will lose some on the way out. The chemical process isn't 100% efficient electrically.  It often generates quite a lot of heat for instance.

    Maybe as much as 10% recovery loss for lead acid - still used in small ups today - bigger battery packs ? - maybe sub 5% for li ion.

    The invertor electronics maybe another few percent in both convertor ac to dc and invertor dc to ac modes.

    One q-cell setup quotes 96% conversion efficiency battery to grid.  

    So likely losses plus simply powering the electronics 24/ 7 could eat up your 2 kWh per day.

    If charge 7-8kWh a day losing even 10-15% is 0.8-1.05 kWh.  

    Tge other 1.0 - 1.2kWh a day averages just 40-50W continuous load - does the electronics loading get built into the  96% type conversion or is there a "constant" vampire type load too.
  • Qyburn
    Qyburn Posts: 3,606 Forumite
    Fifth Anniversary 1,000 Posts Name Dropper
    edited 20 January at 4:57PM
    QrizB said:

    Current clamps aren't particularly accurate.

    You should have a generation meter as well as your import/export smart meter. How does the generation meter compare to the generation totals in the app?
    That's what we find with Solaredge. The app overestimates generation, compared to the generation meter. And underestimates both import and export compared to the smart meter. Taken together that gives the appearance of consuming more than we actually do on days with net export.

    As noted by others the house load and consumption is not directly measured. Looking at the inverter via Modbus it doesn't appear that solar generation is directly measured either, the values for both AC and DC power include both solar and battery power. 
  • matt_drummer
    matt_drummer Posts: 2,009 Forumite
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    The panels generate dc electricity and convert to ac, losses here too in addition to battery losses.
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