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Expanding Existing Solar System and adding battery and keeping fits payments

edited 27 June 2022 at 4:37PM in Green & ethical MoneySaving
15 replies 408 views


  • madwaynemadwayne Forumite
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    The devil will be in the detail
  • michaelsmichaels Forumite
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    Hiya ET, just to be clear, I did get a clear answer from EDF, their green team. The told me on the phone, then twice in e-mails (I found a way to word the questions differently as a double check*) that they do allow a FiT system to be extended. They told me that if I add to my ESE 3.58kWp system, then they would pay FiT's on a ratio of 3.58:X (total kWp) against generation figures supplied.

    For instance, I was hoping to add 1.2kWp at the time from 4 south facing, steep pitched ground mount panels, so FiT would be paid on a ratio of 3.58:4.78 of actual generation.

    In the OP's case, and again purely an example, if they have 2kWp and generate 1,600kWh pa, they get FiT on 1,600kWh. If they add 2kWp, and gen rising to 3,200kWh pa, then they then get FiT apportioned at 2kWp (original FiT approved) : 4kWp (new total), so 3,200 x 2/4 = 1,600kWh.

    So I got the impression that apportioning is how this is done.

    *I asked about replacing 5x 235Wp panels with 350Wp panels, and they confirmed that the ratio for FiTs would be 3.58:4.155. This was also part of me just digging for general info on the issue of replacing failed panels, but being unable to find new ones of the same power, since they've improved so much. Replacing a failed or damaged panel could affect many of us within the 20-25yr FiT period.

    But please, please, please take care. I've never seen anything official saying an original system can't be extended*, but most people in discussions say it can't, which could be a misunderstanding, but does raise alarm bells (for me), so needs to be triple checked before jumping. I also think the OFGEM wording reads negative, until you spot the wording refers to the extension, but it still makes me a tad nervous that it doesn't clearly state that the original FiTs is safe.

    *But the start of that OFGEM guidance scares me:

    10. Can I extend my installation?


    Nice to be able to add better insolated panels, if we added it would be 10 degrees N of E panels to a 10 degrees S of W array so the pro-rata would work against us.  The 'peak shaving' sticking to a 3.68 inverter makes a surprisingly small difference to total output.
    I think....
  • madwaynemadwayne Forumite
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    In reality. I think the system would be as follows:-

    2KW - 2.8KW on the back and inverter
    AC coupled battery storage that can handle excess from the old and the new system (size to be determined but at least 6KW.
    generation meter for second system and export meter for second system if possible.

    so yesterday during the day the solar panels performing badly but enough for my day to day use excluding cooking, kettle, shower. but these would be excluded to a lesser degree on a good day,

    Today they are all over the place 300W to as high as 1.7kW as the sun goes in and out of hiding behind the clouds. (watching the inverter feed it updates every 5 minutes so it is snap shot accurate rather fully reflective.

    (shame I cant clear the clouds directly over the panels, the output on cloudy days would be massively different if i could clear the clouds.)

    My understanding is the AC coupled can effectively be positioned anywhere subject to cable suitability and the brick out building would make sense I suspect rather than in the house, thinking of available space. 

    still waiting for clarifications, so much data out there hard to know what is genuine and what isnt

  • madwaynemadwayne Forumite
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    Ninth Anniversary 10 Posts Combo Breaker
    Wow its shocking got a quote from one company and the plan of the layout clearly has the solar panels over hanging the edge by quite some distance and that isnt allowed.

    some of the other quotes have been dubious and not exactly what was being asked for......the joy
  • Martyn1981Martyn1981 Forumite
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    Hiya. If you go with the single inverter, then double check with your FiT provider first, and get confirmation that they will apportion generation. For instance if you add 2kWp, then they will pay FiT on 50% of generation. If you add 3kWp (panels are getting more efficient/powerful), then they will pay FiT on 40% of generation. I'm registered with EDF for FiT's and that's what they do, but doesn't mean others will. *

    If you have a single inverter, I'm not sure how you would have an export meter for the new array. Also export will be measured for the property, so complications will arise trying to separate generation, even if the new system is separate ...... I think?

    You may find for the combined system that you won't need to go as big with the single inverter, say 3kW for 4kWp, and 4kW (or 3.68kW) for 5kWp(ish).

    A separate system won't mess around with FiT's, but does mean twice the cost in terms of inverters and failures.

    For charging the battery AC, again I don't think there is an issue of 2x charging, as the battery will be taking power from the house, based on the monitored export, so having one or more PV systems wouldn't matter, other than generating more, and exporting/diverting more.

    Don't know if this is possible, but could you have a large battery, that AC charges from the house, but has a direct feed from the new PV into it too, via DC and a charge controller? Would have to be pretty big, otherwise it would cap the new system (I assume?) when the batts get full. Probably a stupid idea I've just made up.

    *Each time this issue comes up it causes confusion. Whilst I have e-mail confirmation from EDF confirming I can add more PV to my ESE system, and have the FiT pro-rata'd, I wouldn't expect anyone to take my word for it, nor EDF's, and certainly not assume that their FiT provider will too.

    However, this very vague comment on the EST website suggests it's alright, but doesn't mention the crucial words 'pro-rata', so could in its ambiguity be a reference to a separate system, but I read it as an addition to a system, since it mentions adding panels:

    Changes to your FIT installation

    Adding capacity

    You can add additional capacity to your installation, for example, additional solar PV panels, without affecting your current FITs payments. However, you cannot apply for additional FITs payments for the ‘new’ capacity.

    This link however is much more clear, but it's a PV business, so hardly concrete proof. 

    Critically, one of two things will then happen – 

    1. The extension would be connected before your existing generation meter. This means that the power generated by the extension would flow through the generation meter that is currently installed. However, because the extension would be ineligible for FIT payments whereas the original system might be, the owner of the asset would be expected to declare the Total Installed Capacity (TIC) of the extension to their FIT licensee and they would simply pro-rata the generation meter reading between the eligible and ineligible systems.
    2. The extension would be connected after your existing generation meter. This means that the power generated by the extension would not flow through the generation meter that is currently installed and no further action would be needed by the owner of the asset.

    OFGEM is also not that helpful, they state:
    10. Can I extend my installation?


    We define an extension to an installation that is receiving Feed-in Tariffs (FIT) payments as additional capacity of the same technology added to the same site. If you extend your FIT installation and the extension is commissioned on or after 15 January 2016, then the new installation is not eligible to receive generation and export payments.

    You can read more information about extensions in our guidance

    Note it says the new installation, which suggests the addition, but could also mean the original, if the old + new are now classed as a new entity.

    In the guidance referenced, it's just as murky referring to 'the extension' rather than the new total. But crucially, none of the guidance says that the original system loses its qualification or will become ineligible, at least they don't make it obvious!!!!! 

    Definition of extension

    3.76. An "extension" to an accredited FIT installation is a modification which increases its TIC from the same eligible low-carbon technology.

    3.77. Any extension to an accredited FIT installation that is commissioned on or after 15 January 2016 is not eligible to receive FIT support. This applies to both generation and export payments.

    So in summary - "Do your own research". Contact your FiT provider and get everything in writing (e-mail) before jumping.

    Today, is a good day!

    I won't suggest anyone struggle through my post above, where I myself tried to struggle through the confusing info out their regarding adding capacity to an existing FiT PV system.

    But I did try to stress, that whilst it does seem OK, and the expanded system will then 'simply' be subject to apportioning, I went on and on ..... and on, about how unclear the info from OFGEM was.

    Well, it seems someone agrees with me, OFGEM!
    In recent years, we have seen an increasing number of queries from generators and industry stakeholders seeking clarity on how certain changes, repairs or replacement of generating equipment may affect an installation’s accreditation to the FIT scheme.1 
    TBF, they posted this guidance before the discussion, and my research, so clearly I didn't look under every stone.

    So here's the full document, it's not exactly clear, in terms of easy reading, but does stress several times that a FiT approved system can be extended, with the FiT provider then apportioning generation. But note, it states and stresses that the FiT provider must be notified, which is totally fair, and I'm not just being a goody two shoes, I think an increase in generation will be thrown up by the computers, and then you'd possibly risk losing all future FiT income (I assume) for mucking about / fraud(?)

    If anyone does have doubts, please read appendix 2 & 3, as suggested, which helps to clarify, and gives examples of how it all works. And if Appendix 2 seems tricky to understand, appendix 3 is, I believe, clearer.

    Feed-in Tariffs (FIT) scheme: Decision on replacement generating equipment

    We are writing to inform you that we have considered stakeholder responses to the changes we proposed on the treatment of replacement generating equipment at an accredited FIT installation. This document sets out our decisions. A summary of responses to the consultation can be found in Appendix 1. The updates we have made to our published FIT guidance documents reflect these changes and are detailed in Appendices 2 and 3. 
    From 15 January 2016, any extensions to an accredited installation’s TIC are not eligible to receive FIT payments. The generator must notify Ofgem and their FIT licensee if they do so and, if generation and export meters are shared, payments will be prorated accordingly.
    Extensions and reductions

    6.4. An extension or reduction is a modification to an accredited installation to increase or decrease its total installed capacity (TIC) from the same type of eligible technology (eg solar PV or wind).

    6.5. This may happen by:
     • adding or removing generating equipment
     • replacing generating equipment with a larger or smaller TIC

    6.6. You must notify your FIT licensee if you extend or reduce the TIC of the accredited installation. If it was accredited under ROO-FIT, you must also inform Ofgem. For information on the difference between the two, see paragraph 2.4.

    6.7. If an extension does not have a separate generation or export meter, readings must be prorated according to TIC, to ensure you are paid correctly. For example, if a 40kW installation has been extended by 10kW:
    • and the extension is accredited, the generator is entitled to payment for 80% of the electricity at the tariff rate(s) of the original installation and 20% at the tariff rate(s)6 of the extension
    • and the extension is not accredited, the generator is only entitled to payment for 80% of the electricity they generate and export

    6.8. Meter readings should be taken on the date of the extension or reduction.

    6.7 refers to accredited or not accredited, the docs go on to explain that this means the extension was eligible for FiT's when carried out, but at a lower rate. Or added after the end of FiT's (15th January 2016).

    I appreciate this is a lot of word salad, but hopefully we can now all relax a bit about replacing damaged panels with newer, but more powerful ones, and all other scenario's, without the spectre of FiT withdrawal hanging over us.

    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
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