We'd like to remind Forumites to please avoid political debate on the Forum... Read More »
We're aware that some users are experiencing technical issues which the team are working to resolve. See the Community Noticeboard for more info. Thank you for your patience.
📨 Have you signed up to the Forum's new Email Digest yet? Get a selection of trending threads sent straight to your inbox daily, weekly or monthly!
Solar installed then consumption apparently increased by ~60kw per month
Options

petalouthi
Posts: 18 Forumite

in Energy
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?
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?
0
Comments
-
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!2 -
Has your annual consumption actually increased by the 720kWh?1
-
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.3 -
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?1
-
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 !2
-
What does your actual electricity meter show? If that isn't increased by 60kWh a month then it's the app giving erroneous dataRemember the saying: if it looks too good to be true it almost certainly is.1
-
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 dataSo 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!2 -
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.1 -
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?
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.2 -
The panels generate dc electricity and convert to ac, losses here too in addition to battery losses.2
Confirm your email address to Create Threads and Reply

Categories
- All Categories
- 351K Banking & Borrowing
- 253.1K Reduce Debt & Boost Income
- 453.6K Spending & Discounts
- 244K Work, Benefits & Business
- 598.9K Mortgages, Homes & Bills
- 176.9K Life & Family
- 257.3K Travel & Transport
- 1.5M Hobbies & Leisure
- 16.1K Discuss & Feedback
- 37.6K Read-Only Boards