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

petalouthi

matt_drummer said:

The panels generate dc electricity and convert to ac, losses here too in addition to battery losses.

Thanks - I'm getting a picture of where the efficiency losses might be occurring. So do you think QCells are wrong to assert that the inverter only uses 10w/hour - see above?

petalouthi

wrf12345 said:

Out of interest, are you better off financially on the bills despite the increased usage, if you are getting lots of solar/battery export money then the cost of running them does not really matter?

Yes - definitely better off financially. The system is working well and we exported 2580kw up to 07/01/25, most at 15p/kw. By coincidence this just about matches our consumption before installation, so even with the apparent extra consumption since it's a good result. If the extra consumption is just a function of having the system, or if it's the app over-reading generation, then that's fine, but if it's some fault we would like to be able to pin it down and get it fixed.

petalouthi

Thanks for all the comments. I've tried to answer each with more details, and would be interested in any further observations.

It seems that the extra apparent consumption could well be actual consumption by the system itself, or it could be overmeasuring of generation by the app. But if it's a fault then we'd like to get it fixed.

If anyone can help on the Generation meter problem we'd be very grateful, as this might help on the second possibility.

tim_p

petalouthi said:

tim_p said:

Has your annual consumption actually increased by the 720kWh?

Consumption measured from meter 07/12/21-07/12/22=2598

Consumption measured from meter 07/12/22-07/12/23=2580(includes 1st few days after installation on 22/11/23, when measured from app)

Consumption from QCells app 07/12/23-07/12/24=3255

So it's increased by 675 from '23, and 657 from '22 figures

Do you have any figures from the summer months?  My system with 3 inverters used next to nothing (50kWh total) between March and Aug (168 days). Solar and battery covered the lot. 

Qyburn

petalouthi said:

Consumption from QCells app 07/12/23-07/12/24=3255

What does your actual meter show for that period? Actual readings from the smart meter. Another design question. I see you have a battery, when you're drawing from the battery does that go through the same inverter and through the generation meter? A schematic would help, you should have received one with the MCS and other paperwork.

QrizB

petalouthi said:

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?

Ah yes - the Generation meter, and also another extra meter labelled "Energy meter" and also referred to as CHINTS meter by QCells. Both meters started at zero on installation.

We thought this might be a good independant means of looking at generation. But we can't make sense of readings on these meters, they seem all over the place. Some examples

Looking at your numbers:

petalouthi said:

from installation (22/11/23) to 07/01/25

QCells app total generation=4735kw

Gen. meter import reading=4919

Gen. meter export reading=1168

CHINT import reading=42.57

CHINT export reading=63.30

I honestly don't know what the CHINT meter is reading (you'd need to check the circuit diagram for your installation, or physically trace the cables) but the rest tell a story.

I'm assuming that your battery is attached to your solar inverter, ie. it's a hybrid inveter. It's the easiest way to make sense of your readings.

If tht assumption is correct, the "gen meter export" is actually measuring the electricity flowing into the battery from the mains, and the "gen meter import" is measuring the tlectricity flowing from your (battery+solar) into your home. So during that period you put 1168kWh into your battery from the mains and took 4919kWh out of your (battery+solar). Which means that your solar panels generated (4919-1168) 3751kWh net of inverter losses.

This suggests to me that the QCells app is either (a) extremely inaccurate or (b) isn't measuring what it thinks it's measuring.

petalouthi said:

tim_p said:

Has your annual consumption actually increased by the 720kWh?

Consumption measured from meter 07/12/21-07/12/22=2598

Consumption measured from meter 07/12/22-07/12/23=2580(includes 1st few days after installation on 22/11/23, when measured from app)

Consumption from QCells app 07/12/23-07/12/24=3255

So it's increased by 675 from '23, and 657 from '22 figures

Again, see my comments above on the QCells app. It could well be over-reading.

Can you tell me how much your mains supply meter thinks you have imported and exported during the same period, 22/11/23 to 07/01/25? Or the closest similar period you have raeadings for?

petalouthi

tim_p said:

petalouthi said:

tim_p said:

Has your annual consumption actually increased by the 720kWh?

Consumption measured from meter 07/12/21-07/12/22=2598

Consumption measured from meter 07/12/22-07/12/23=2580(includes 1st few days after installation on 22/11/23, when measured from app)

Consumption from QCells app 07/12/23-07/12/24=3255

So it's increased by 675 from '23, and 657 from '22 figures

Do you have any figures from the summer months?  My system with 3 inverters used next to nothing (50kWh total) between March and Aug (168 days). Solar and battery covered the lot. 

Here are some stats from 07/03/24 to 07/09/24 - roughly Mar to Aug. I think the system was still importing at night during the first part of this period, hence higher import, but also higher export of excess (prices were the same for import during the night and for export during most of the day). Import and export figures from readings from smartmeter, generation figures from app, as have no other way to get these - see above on Generation meter.

07/03-07/04: Imp. 159, Exp. 173, Gen. 368

07/04-07/05: Imp. 135, Exp. 294, Gen. 503

07/05-07/06: Imp. 60, Exp. 450, Gen. 643

07/06-07/07: Imp. 5, Exp. 435, Gen. 651

07/07-07/08: Imp. 5, Exp. 357, Gen. 594

07/08-07/09: Imp. 17, Exp. 286, Gen. 505

petalouthi

Qyburn said:

petalouthi said:

Consumption from QCells app 07/12/23-07/12/24=3255

What does your actual meter show for that period? Actual readings from the smart meter. Another design question. I see you have a battery, when you're drawing from the battery does that go through the same inverter and through the generation meter? A schematic would help, you should have received one with the MCS and other paperwork.

Yes, anything drawn from, or sent to, battery goes through inverter. I'll have to look to see if there is a diagram of the system and get back to you on that.

All the import and export figures and readings I've quoted come from the smartmeter, as do consumption figures prior to installation on 22/11/23. I don't have any way of getting at consumption since then, or generation, other than the app.

from smartmeter period 07/12/23-07/12/24:

import total=1390

export total=2575

from app same period:

consumption=3255

generation=4578

petalouthi

Thanks for all the comments so far - definitely very helpful. QrizB - I need a bit more time to absorb what you're saying and will reply in detail as soon as I can. And I'll look for a diagram of the system as asked by Qyburn.

Qyburn

I suspect that your Qcells app gets hopelessly confused tracking energy imported to the battery and then later used. Our Solaredge certainly does, it messes generation figures up. It and also screws up readings from the generation meter, which is a real and presumably accurate meter but can't of course tell whether the power has come from solar or from the battery.

So taking a real high level view and assuming the battery is 100% efficient, how do your figures look if we assume your home used the same as the previous year, 2600kWh?

Home use 2,600, import 1,390, so the other 1,210 came from solar
Exported 2,575 making total generation 3,785kWh. Is that in line with your expectations?