Solar panels and battery - any real world recommendations?

I'm getting a very weird issue where my system (Fox, using the FoxCloud app) is reporting tiny amounts of grid consumption each day (<0.1kWh) as I'd expect at the moment, but Octopus has me drawing c9kWh a day, most of which is outside of peak sun periods. I'm struggling to understand this - I've disabled charge from grid given how much generation we are getting at the moment, and 9kWh seems very high just to run the inverter!

Any ideas?
 
Sounds to me like your inverter CT/meter is in the wrong place and not seeing your house loads. Is your battery discharging as you'd expect?

It's rather unlikely (albeit, not impossible) that your DNO meter is wrong to the tune of 9 kWh.
 
One More Solo said:
I'm getting a very weird issue where my system (Fox, using the FoxCloud app) is reporting tiny amounts of grid consumption each day (<0.1kWh) as I'd expect at the moment, but Octopus has me drawing c9kWh a day, most of which is outside of peak sun periods. I'm struggling to understand this - I've disabled charge from grid given how much generation we are getting at the moment, and 9kWh seems very high just to run the inverter!

Any ideas?
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Can you post a screenshot from the app of the daily graph showing load, grid, battery and solar?

As said above, the CT should show all grid use (even from battery charging) and export so it sounds like it's in the wrong place or has failed.

Mind you, Octopus grid use figures are always wrong in the app for me but correct on my bill, so it could be them too.
 
reef said:
Can you post a screenshot from the app of the daily graph showing load, grid, battery and solar?

As said above, the CT should show all grid use (even from battery charging) and export so it sounds like it's in the wrong place or has failed.

Mind you, Octopus grid use figures are always wrong in the app for me but correct on my bill, so it could be them too.
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I've attached an image from the 5th below where I had slightly less generation so more of the battery was used - it was down to 90% before charging over the course of the day. Fox reckons 0.1kWH for the day and Octopus reckons 6.7kWh. I don't understand how that's possible if I'm not anywhere near the minimum discharge for the battery.


host photos
 
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Thank you very much Mr @b0rn2sk8 - your answer really helped me.

I have a Powerwall 3 and I'm on Octopus Intelligent Go tariff. What is the best way to manage the battery charging, so it's charged when the low price is active during the day?

I've heard Netzero and Home Assistant can do it. What would you recommend?

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Basically you charge it up to 100% between 23:30 and 05:30 and run entirely on grid in those times. If octopus also give you any cheap slots outside of these times, you also charge it up to 100% and stay on grid.

This is the same regardless as to whether you have solar or not. Cheap grid is 7p/kwh, solar exports is 15p/kwh. Buying from the grid is cheaper than using your solar so you want to export as much of it as possible.

If you are wanting to totally max it out, you’d also force export your battery to the grid at the end of the day, leaving just enough for you to get to 23:30 again.

Home assistant is ‘free’ (you need the hardware to run it on). You’ll also need:
Tesla add on for controlling the Powerwall.
Octopus add on so can automate the battery to charge when you have 7p electricity (and to discharge at the end of the day).

You can use the Predbat add on for home assistant to fully automate it all for you (you’ll still need the Octopus and Tesla add ons). It will schedule your charging and discharging cycles based on the pricing signals from Octopus (including savings sessions etc.) and your real energy usage. The algorithm runs every 5 mins or so and updates the schedule as needed.
 
One More Solo said:
I've attached an image from the 5th below where I had slightly less generation so more of the battery was used - it was down to 90% before charging over the course of the day. Fox reckons 0.1kWH for the day and Octopus reckons 6.7kWh. I don't understand how that's possible if I'm not anywhere near the minimum discharge for the battery.


host photos
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The load is pretty much matching your solar production on there so the CT clamp is not reading properly or is in the wrong location. If the inverter cannot correctly see the grid and house load it won't use the battery. It'll charge up from solar still as it knows the SOC and solar coming in but that's about it. The drop in SOC is just what it is using to keep the BMS and inverter awake at night.
 
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reef said:
The load is pretty much matching your solar production on there so the CT clamp is not reading properly or is in the wrong location. If the inverter cannot correctly see the grid and house load it won't use the battery. It'll charge up from solar still as it knows the SOC and solar coming in but that's about it. The drop in SOC is just what it is using to keep the BMS and inverter awake at night.
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I think the reason the load is matching the solar (or close) is we’re export limited so think the installers have applied a dummy load to keep export to 3.68kwh. We’re still waiting on approval from the DNO so our export is currently capped to nil from what I can tell.
 
One More Solo said:
I think the reason the load is matching the solar (or close) is we’re export limited so think the installers have applied a dummy load to keep export to 3.68kwh. We’re still waiting on approval from the DNO so our export is currently capped to nil from what I can tell.
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The load matching the solar only happens when the inverter cannot see the grid. If it was correct it would use the battery to see to the house load and your consumption figures would match Octopus' figures. This is the case even with export capped.

As it stands the inverter cannot see the grid so will simply export all solar, but with the export capped to zero will just sit idle, unless the battery needs charging.
 
Is there a way to directly control the Powerwall - tell it to start charging or start discharging now?

Completely unrelated, I got this crazy idea in the shower today.

Aiko Solar is the 3rd largest solar panels manufacturer in China and their market cap is 2.7B pounds. Which is a very small part of the UK government green transition budget. They make enough panels in a year, that if installed in will cover 10% of it's electricity consumption. So have the government or a British company buy Aiko. Pay salaries and materials, deploy all panels in UK and in 10 or 20 years the country will have enough green energy production to cover 100%+ of it's needs.

There are also a few big battery manufacturers in China with market caps in the range of 1B - 2B pounds. Buy a few of these as well, deploy the batteries they make in UK to store the electricity produced by the Aiko panels.

This way by 2045 UK won't need to use any nuclear, coal or gas for electric production.

Surely this is cheaper and safer than deploying French built nuclear reactors :)

And yeah I know about the slave labor in China and the potential political barriers to implementing such a plan.
 
Solar Panel Degradation

It has been a while since I have posted so I will give a recap. (I am on PV Output as Give me sunshine and Give me sunshine2)

In October 2011 I installed 17 x 235 Sanyo Panels. They were great. In the first 10 years we produced 43638kw.

In September 2021 I installed a further 4.8kw of panels on my east roof and 5.6kw on my south roof which were side by side with my original Sanyo's.

All went well for a while but I noticed that the Sanyo's no longer were achieving the high numbers they used to do so I went back over the figures to check. Having separate figures for my new and old panels that were next to each other did mean I could accurately track what had happened. For 11 years, I think there was either no degradation or so little as to be irrelevant.

In the 18 months ending in October 2024 (when my Sanyo's were exactly 13 years old) I was now able to state that the performance had dropped off by about 12.5%. I could look up the daily/monthly figures for 2 sets of panels side by side so effectively I could use my new panels as a control sample. I looked up my warranty which guaranteed 90% at the end of 10 years and 80% at the end of 20 years. Most panels seem to talk about a gradual decline but I am certain this has not been true in my case. I could carry on or I could replace all my original panels. I had 12 years left on my 25 year contract. Nobody has ever had panels improving with age.......like fine wine.

In the end I decided to replace my Sanyo's. By rejigging the layout slightly I was able to add another 1.41kw which have been wired into the eastern inverter. We have 3 inverters. My original one, a hybrid run from the new south panels and one from the Eastern side. I was trying to catch up with some of the rest of you. As we all agree the cost of the panels is the lowest solar expense.

Assuming I get back my 12.5% output from the new panels, and that the extra money from the tax free index linked FIT payments are regarded as interest on the money I no longer have, then I calculate I will just about come out ahead. The panels I installed in 2021 were Hyundai shingle 400watt, as I do have low shading problems on my eastern roof. In the table below the Sanyo's are called Pan as Panasonic took over Sanyo and rebranded them and the Hyundai are Hy


First 11 years average output
OutputOutputPan vs Hy
Pan Outputper kwHy outputper kw
Year 11October
November
December
January
February
March
April
May
June
July
August
September
Year 12October
November
December
January
February
March
April
May
June
July
August
September
Year 13October
November
December
January
February
March
April
May
June
July
August
September
Year 14October
November
December
January
February
March
April
May
June
 
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Peteronthesouthcoast said:
No, but the voltage on both stings had not dropped, and they have been consistent
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I thought the MPPT could change that anyway as part of the optimisation.

What you describe sounds like when something fails and not degradation.
Everything I have ever read says panels degrade slowly and constantly as they slowly break down over time with solar exposure.
 
DRZ said:
Yesterday was a new record for me at 69.1kWh. Today looked like it might have beaten that but the afternoon was very choppy so ended up on 'just' 65.65.

I'm about to post some thoughts in the other thread on this too...
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My SE-facing panels are split across my two inverters, 3960w on each. Unfortunately, one of them is a 3.68kW inverter so spends most of the day (11-4) clipping. This is only costing me 1.4kWh each day so I can live with it but it is the reason why I haven't broken 70kWh yet. I have been pondering what I can do about this and realistically there isn't anything I can do. I didn't think I would be clipped so much of the time when I was thinking about all of this, so there's almost nothing cost-effective that I can do. 1.4kWh a day is ~21p/day so it would take decades to pay back if I added more capacity. I've considered rearranging the strings so as to move one panel across to the other inverter but again the costs involved in doing that are not trivial enough to ever warrant payback.

I'm not after any sort of reply/solution, just shouting into the abyss really.
 
Hi all, new to Home and Gardens :)

Getting a new Solar Set up in SE MCR. House is South Facing so should be good generation. From experience, how long does it take to get the green light from the DNO to proceed with the installation ?
 
@Loki you don't need the dno approval for installation, you'd need it for the export. Your installer should do this for you. If less than 3.68kw export it's a notification, so approval not required per se. If more than that then will need g99 approval, I'm not sure how long this takes though.
To get paid for the export (SEG) can take a week or more, depending on which supplier you are using.
 
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