Solar panel production figures

Hi guys and girls,
Me again with the 17x395 solar array the 5.21kWh battery and the suspiciously undersized 3.6kW inverter

I've been back and forth with the installers.

They've said
3.6kw is the maximum you can export back to the grid without DNO approval. Often when we apply for DNO approval for larger inverters they still ask for the export to be limited on the inverter settings anyway to avoid overloading the infrastructure
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And my response was this

I asked before placing the order if we had been specced a 3.6kW to avoid DNO approval and was told that wasn't the case. It was because with our panels across 2 roofs (7SE and 10SW) that we would never exceed 3.6kW of PV production.

That is already apparent to not be true as even now in Feb we have seen the inverter limiting pv output to 3.6kW once the battery was full. Also with the max ac output of 3.6kW, during the day when we've seen a large household load. We have had to discharge the battery instead of using all of the available PV.

I understand the 7.2kW MPPT but it seems in our household with 6.7kW of panels and a 5.12kWh battery. The inverter will spend large parts of the day certainly towards summer with the battery full, and limiting export to 3.6kW. Which seems a huge waste given that what made this initial outlay viable was the export. We have a forecast surplus of over 2000kWh per year spare that we might not be able to sell as proposed.

I feel like having seen how the system behaves, we should have either had a larger battery capacity or inverter.
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A, do I sound a plonker/ do I have a point?
B, what should I push for? A 5kW inverter is only £400 more Inc vat. I wouldn't mind paying the difference but on the basis I feel slightly misguided by them, perhaps I should argue the point if we get to that.
C, is the DNO point he raised valid? They might cap my export to 3.6kW? Even so, at least I'd be able to better use all the available PV in the house...

Appreciate your input, please keep it coming:)
 
gpuerrilla said:
Thanks for mentioning. We had the broadband provider with a planned outage last week and because it was off from 5am till about 11am the inverter/dongle must have gave up trying to connect so for that day it was mostly unlogged on their api.

When I had it today I thought is the dongle on the blink, but that explains the drop. I would get the ethernet adaptor but its not played up that much since we had it.
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Im glad i randomly poked my head in here, as i had the exact same thing too and was pulling my hair out as there is an AP less than 12ft from the dongle :)
 
NoNameNoNumber said:
Hi guys and girls,
Me again with the 17x395 solar array the 5.21kWh battery and the suspiciously undersized 3.6kW inverter

I've been back and forth with the installers.

They've said


And my response was this



A, do I sound a plonker/ do I have a point?
B, what should I push for? A 5kW inverter is only £400 more Inc vat. I wouldn't mind paying the difference but on the basis I feel slightly misguided by them, perhaps I should argue the point if we get to that.
C, is the DNO point he raised valid? They might cap my export to 3.6kW? Even so, at least I'd be able to better use all the available PV in the house...

Appreciate your input, please keep it coming:)
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even if the export is limited to 3.6kw......you could be filling the battery and exporting at the same time, with a bigger inverter. Therefore spreading how the power is used. With some systems you can tell it what to do, i'm sure thats right but others will chime in if im wrong.

You could be producing 7kwh on the panels send 50% to the grid, then the panel, then the rest to the battery........or panel, grid, battery
 
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Diagro said:
Free? Did you get the panels for free?
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Well no of course not. Its practically impossible to assign a cost to those units since I do not know what the total generation of my system will be over x years etc
Plus lets not get into sunk costs and all that ;)
Really it was a gripe that of all the days to be complaining about generating a lot it would end up being on a savings session day.
Today for example will be less and I would have been overjoyed to have flipped the days generations ;)

Freefaller said:
He may have already hit his ROI and as such it would be effectively free.
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Also I only had the system installed in late Nov (nov generation was 6 days).

I have generated a benefit of £323 from install to end of Jan though.
Combination of actual generation (inc diversion to tank), cheaper elec via Go (compared to 34p rate), savings sessions rewards (wouldn't have happened without the solar)
That is 2.4% of outlay recovered. I should be inline for around 20% this year unless elec prices fall off a cliff, or I get stitched up on rate come end of Sept when my Go Tariff ends.

If teh standard elec cost goes up in April that will accelerate my closing in on return of capital deployed.

Plus for me whilst the numbers had to work, it was at least partially wanting to do the the right thing.
I am no eco warrior, but I am not blind and can see the impact of climate change, so happy to start down the correct road. (I am just not ready yet to give up ICE or gas heating)
 
Mercenary Keyboard Warrior said:
Well no of course not. Its practically impossible to assign a cost to those units since I do not know what the total generation of my system will be over x years etc
Plus lets not get into sunk costs and all that ;)
Really it was a gripe that of all the days to be complaining about generating a lot it would end up being on a savings session day.
Today for example will be less and I would have been overjoyed to have flipped the days generations ;)



Also I only had the system installed in late Nov (nov generation was 6 days).

I have generated a benefit of £323 from install to end of Jan though.
Combination of actual generation (inc diversion to tank), cheaper elec via Go (compared to 34p rate), savings sessions rewards (wouldn't have happened without the solar)
That is 2.4% of outlay recovered. I should be inline for around 20% this year unless elec prices fall off a cliff, or I get stitched up on rate come end of Sept when my Go Tariff ends.

If teh standard elec cost goes up in April that will accelerate my closing in on return of capital deployed.

Plus for me whilst the numbers had to work, it was at least partially wanting to do the the right thing.
I am no eco warrior, but I am not blind and can see the impact of climate change, so happy to start down the correct road. (I am just not ready yet to give up ICE or gas heating)
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So... not free then.

Blooming expensive really.

You know its true.
 
Diagro said:
So... not free then.

Blooming expensive really.

You know its true.
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What?

I know that I should get my payback in around 6 years, and then I will be on genuinely free electric.

My unit cost average (taking into account the above) worked out at 5.3 pence per kwh in Jan. When talking from a cashflow perspective.
Thats a lot closer to free than the 34p most people are paying ;)

If you want to get into a deep conversation on marginal costing and expected units costs over lifetime of the array then I would need to do a bit more modelling. I suspect you don't though.

If you buy a new car do you immediately take the cost over the first months usage when working out your travelling costs?

If you want it in other terms, I expect to generate around 3x more value of units over 15 years than the cost of the array and batteries.
Which I would estimate over current pricing would give me a unit cost (per kWh) discount of around 20p per unit at current pricing. (Jan was exceptional due to savings sessions.)
 
Mercenary Keyboard Warrior said:
What?

I know that I should get my payback in around 6 years, and then I will be on genuinely free electric.

My unit cost average (taking into account the above) worked out at 5.3 pence per kwh in Jan. When talking from a cashflow perspective.
Thats a lot closer to free than the 34p most people are paying ;)

If you want to get into a deep conversation on marginal costing and expected units costs over lifetime of the array then I would need to do a bit more modelling. I suspect you don't though.

If you buy a new car do you immediately take the cost over the first months usage when working out your travelling costs?

If you want it in other terms, I expect to generate around 3x more value of units over 15 years than the cost of the array and batteries.
Which I would estimate over current pricing would give me a unit cost (per kWh) discount of around 20p per unit at current pricing. (Jan was exceptional due to savings sessions.)
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What happens if your battery stops functioning outside of warranty?
What if you get some RISO faults on your string? Knocking the entire string off? Who stumps up the cost of repairs? DON'T expect the installers to, or the panel / battery manufactures to help.
Yes, solar works. I know it does. I'm watching the second by second output from around 50MegaWatt of Solar as we speak.. However, I do not agree that domestic solar works. Especially with the upfront costs, and risk of loss 10 years down the line when it all breaks down.
 
gpuerrilla said:
No matter how sceptical you are, when your electricity supplier ups your price threefold with no sign of it coming down the ROI isn't nowhere as bad as it was 5 years or more ago.
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I'm not sceptical. I just see the numbers and refuse to accept it as a viable option.
I however, have 4kw of panels being installed asap anyway.
But I got my panels for free so... the numbers now make sense ;P
 
Diagro said:
What happens if your battery stops functioning outside of warranty?
What if you get some RISO faults on your string? Knocking the entire string off? Who stumps up the cost of repairs? DON'T expect the installers to, or the panel / battery manufactures to help.
Yes, solar works. I know it does. I'm watching the second by second output from around 50MegaWatt of Solar as we speak.. However, I do not agree that domestic solar works. Especially with the upfront costs, and risk of loss 10 years down the line when it all breaks down.
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Outside warranty?, I buy new. Its 10 years so by then i will almost certainly have got more than my money back from them.
They are listed as 80% when they hit 10 years. Most likely thing to go wrong is actually inverter.
I wouldn't expect the installers to be doing anything at 10 years no. Again it should have paid for itself way before then.

If I get 10 years in and its all paid for i may well change the majority of the system at that point.
As panels get better, I honestly think we may see more with in built water then, for cooling but also for heat harvesting.

Its funny we have opposite views, I think solar is perfect for domestic with some batteries, but would prefer we stopped large scale solar farms and built more wind instead.
 
Depending on your installer panels can have up to 25 years warranty, and the batteries are 15 I think.

With the cost of installation and the amount I'm saving monthly on gas and electricity I will (if rates stay the same) break even in about 5 years. Which means that if it goes wrong after that I've already broken even. Ultimately, I will probably upgrade my inverter at some point anyway. The panels are very unlikely to go wrong. You're getting them for free so just enjoy it, you can look down your nose and mock but I don't think you really understand the impact it'll have.

It's adding value to my home, but also it's not a huge amount of money in the grand scheme of things (less if you take a loan out). Psychologically it's more than halved my utility bills on a monthly basis and that has a massive impact. Also importantly it has a significant positive ecological impact which I feel is important.

Heck even if I had taken a loan out, you'd still break even fairly quickly, and the repayments would be offset by the reduction in utility bills. In the summer I'd be surprised if I don't actually net £40+ per month.

Ultimately for me it impacts me in the "here and now" whilst electricity and gas prices are so high - regardless of your perspective, and you can interpret it whichever way you want, as PV owners you are getting "free" electricity.

Sure things can go wrong, but that's what insurance and warranties are for! :)

You may disagree with this but honestly once you've invested in them the "value" you get is higher than the actual ROI.
 
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Mercenary Keyboard Warrior said:
Outside warranty?, I buy new. Its 10 years so by then i will almost certainly have got more than my money back from them.
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Also ten years in a progressive technology like battery storage or solar equipment in general, moves quite rapid so equipment hopefully not only get better priced (cheaper) but is more efficient/smaller/productive etc. As you said its the inverter that historically seems to fail early which is why you dyor on them and budget accordingly.
 
Mercenary Keyboard Warrior said:
Outside warranty?, I buy new. Its 10 years so by then i will almost certainly have got more than my money back from them.
They are listed as 80% when they hit 10 years. Most likely thing to go wrong is actually inverter.
I wouldn't expect the installers to be doing anything at 10 years no. Again it should have paid for itself way before then.

If I get 10 years in and its all paid for i may well change the majority of the system at that point.
As panels get better, I honestly think we may see more with in built water then, for cooling but also for heat harvesting.

Its funny we have opposite views, I think solar is perfect for domestic with some batteries, but would prefer we stopped large scale solar farms and built more wind instead.
Click to expand...
I've got a Solar park on my books. 14 Inverter failures and errm.. 7300 Panel failures within 10 years.
 
gpuerrilla said:
Also ten years in a progressive technology like battery storage or solar equipment in general, moves quite rapid so equipment hopefully not only get better priced (cheaper) but is more efficient/smaller/productive etc. As you said its the inverter that historically seems to fail early which is why you dyor on them and budget accordingly.
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Exactly. 10 years from now I expect we will see many more options. Much better controls etc etc
They will never be worthless. I would love an old 8kwh house battery for my allotment, even if its only got 30% usable capacity, couple of panels, small inverter to get me 1kw usable would be absolute dream in my allotment shed ;)
 
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