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Leaf 30kWh, Outlander PHEV
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I am going through that process at the moment so know a bit about removing a defunct chimney. I'm mostly taking it down due to a leak which I think is from the top haunching, but to be honest I don't need the chimney, it's draughty, and the chimney breast takes up a lot of space in one of the bedrooms. I submitted a simple building control notice which I think cost me £130 as the total cost was under £2k. I got in a Structual Engineer to do calculations on replacement timbers on the roof. That cost me about £300. As I mentioned earlier the biggest cost will be scaffolding. But the OP may want to strongly consider a SE anyway to check the roof timbers can support the additional weight of the panels. I know if I was buying house with PV on, Id be mostly concerned about the integrity of the roof structure and waterproofing.

@Trevor Larkum - do you install in-roof pv? Someone on here posted some photos of their property, which was almost like a replacement roof from metal sheet panels, with the PV bolted through. There were no tiles under the panels. Seemed a very smart way to reduce unnecessary loading and avoid hooks etc.
1.6m x 1.0m panels weigh about 18kg. I think the tiles weigh significantly more especially when wet.


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IF you're interested in my Input

Also, I suggest to have a look at
Your Longi 360Wp panels are really only 300Wp equivalent of a better brand panel.
A better brand panel will last you a lifetime.
The Chinese stuff, who knows how long they'll last and if they'll be around to honor warranties.
You would think so but my experience says otherwise. I have identical 360 w longi panels 2 equal strings. Each string should output max 2880w. Inverter is 5kw. There are a few data points where one string pulls 3000w and the other 2000w. Usually they are pretty even but I get a fair bit of pigeon droppings on one until it rains.
I am also astonished at the length of time I can get full inverter output from 11am to 4pm and this was beginning of April living in N England. Maybe at this performance they won't last as long :)
 

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@Trevor Larkum - do you install in-roof pv? Someone on here posted some photos of their property, which was almost like a replacement roof from metal sheet panels, with the PV bolted through. There were no tiles under the panels. Seemed a very smart way to reduce unnecessary loading and avoid hooks etc.
We do install in-roof PV, yes. They are popular because of aesthetics but cost perhaps 20% more. They may operate a little less efficiently because of heat build-up, but they do include some integral ventilation channels. They make a lot of sense if your roof needs work anyway as they replace a lot of expensive tiles (plus you get to save on scaffolding).
 

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Leaf 30kWh, Outlander PHEV
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We do install in-roof PV, yes. They are popular because of aesthetics but cost perhaps 20% more. They may operate a little less efficiently because of heat build-up, but they do include some integral ventilation channels. They make a lot of sense if your roof needs work anyway as they replace a lot of expensive tiles (plus you get to save on scaffolding).
Maybe I should get you to do me a quote too. I’m just outside London EN7 6TT.

South facing roof is 4.2m x 4.2m. I do have a chunk of east and west facing roof too


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Thanks for the clarification Trevor. That's a shame. I've still got 15 years of FIT to claim so that's a non-starter.
I've had a further dig into this, and it does seem possible to keep your FIT while extending a PV installation, you just get the FIT pro-rated...


I've emailed my FIT provider to see what they say.
 

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I've had a further dig into this, and it does seem possible to keep your FIT while extending a PV installation, you just get the FIT pro-rated...
I've emailed my FIT provider to see what they say.
I'd be interested in hearing the outcome of that. Presumably you'd like to do it because your inverter is rated pretty high compared to the power of the existing panels? Otherwise you run the risk of losing out on FIT payments (your payments get reduced by the amount of extra panels, but you don't generate more because the inverter was the limit).

I'm also skeptical of advice in that thread, for example:
If I were you this is what I’d do:
- Find some cheap “used” panels on eBay. Look for nearly-new panels that are closeby. Have a measure as to what you can fit in your car with the seats folded, 1600x900 might be a little big for your leaf. Maybe a friend with a bigger car /van will help you out? Do you have a roof rack?
- Buy a suitable additional inverter.
- Either connect the inverter to the same breaker as your current inverter (CU side of the generation meter) or add an additional breaker for the new inverter. Either way you need a rotary isolator by the CU between the CU and the inverter.
- Profit.

A completely achievable DIY project. No need to trouble the DNO...
Seems to me to be illegal.
 

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I'd be interested in hearing the outcome of that. Presumably you'd like to do it because your inverter is rated pretty high compared to the power of the existing panels? Otherwise you run the risk of losing out on FIT payments (your payments get reduced by the amount of extra panels, but you don't generate more because the inverter was the limit).

I'm also skeptical of advice in that thread, for example:


Seems to me to be illegal.
Hi Trevor.

I'd agree some of the advice is a bit off. My current system (standard 4kWp E/W split with 3.68kW dual string inverter) fills the central part of the roof, so not much room for a parallel install (that doesn't look weird, disturb the existing system, or go through the generation meter).

My hope is that I can simply replace the entire installation (panels and inverter) with a setup double the kWp size, then halve the generation meter readings for FIT purposes. The FIT guide does mention pro-rated payments. I'd also then have a 'spare' 4kWp system that I could sell to recoup some cost.

I'm probably being optimistic that both the DNO and FIT provider would agree to this, but it's worth asking. I suspect there are quite a few PV owners who were 'early to the game' who would like to upgrade their systems to newer specs.

I'll update this thread when I get a reply from our FIT provider.
 

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My hope is that I can simply replace the entire installation (panels and inverter) with a setup double the kWp size, then halve the generation meter readings for FIT purposes. The FIT guide does mention pro-rated payments. I'd also then have a 'spare' 4kWp system that I could sell to recoup some cost.

I'm probably being optimistic that both the DNO and FIT provider would agree to this, but it's worth asking. I suspect there are quite a few PV owners who were 'early to the game' who would like to upgrade their systems to newer specs.
I'd be surprised if they agreed - that could kickstart a whole upgrade industry! - but if you don't ask you don't get.
 

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I'd be surprised if they agreed - that could kickstart a whole upgrade industry! - but if you don't ask you don't get.
Quick update. I've had my first reply from my FIT provider. They say it's reasonably common to have requests for pro-rating a generation meter reading, due to additional (post-FIT) panels being added to an existing FIT system. They can accommodate these, and also like for like replacements, due to failure etc.

But they (the guy checked with the rest of his team too) have never had a request to replace an FIT system with an entirely new system of larger capacity, then pro-rating the generation meter.

He agreed that the guidance isn't clear on this idea, so he has raised a clarification request from Ofgem. I'll let you all know what the outcome is.
 

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Does the FIT scheme have an allowance for degradation of the panels? If a system with a higher rating is capped then it will not suffer from reduced output from degradation.

Also, wouldn't a 10kW peak install limited to 4kW give higher return than a plain 4kW system? What are the maths like?
There is no allowance for degradation, you're just paid for how many kWh go through the meter. So yes the 10kW system would give 4kW more consistently through the year.
 
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