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Discussion Starter #1
"Q: I have a 3kw solar PV system installed for 3 years now. Originally the roof suffered from shading but I have now removed a tree so could fit another one or two panels. I purchased an extra two panels originally as spares. Could I fit these (using an accredited fitter) and claim the feed-in tariff (FIT) on the new rate for the extra panel? (I don't need to change the inverter as it's within the tolerance with the extra panel). Would I need an extra export meter for the extra panel or could it be calculated pro-rata?"

http://www.yougen.co.uk/blog-entry/2378/What are the rules about extending my solar panels'3F/
 

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Read and understood however what's to stop you sneaking on the other panels? as the power output per year is dependant on the sun and the location and is variable not sure that they would spot the difference? unless they actually checked the property of course?
 

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Good points on the above. Something which I am confused by is why, if you CAN overspec the panels into the inverter why you are not allowed to have more than 4kw worth of panels in the UK.

I have 16 panels of 240W each so I am at 3.84. I asked the installer whether it would be worth adding a 17th (I have loads of roof space) but he said that no, you cannot do it legally
 

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Good points on the above. Something which I am confused by is why, if you CAN overspec the panels into the inverter why you are not allowed to have more than 4kw worth of panels in the UK.

I have 16 panels of 240W each so I am at 3.84. I asked the installer whether it would be worth adding a 17th (I have loads of roof space) but he said that no, you cannot do it legally
Oh really? I hadn't heard that before.
 

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Read and understood however what's to stop you sneaking on the other panels? as the power output per year is dependant on the sun and the location and is variable not sure that they would spot the difference? unless they actually checked the property of course?
It is clear from the communications I get from my FIT provider (Ecotricity) that the generation figures from the meter are checked against your history and against what is likely from an array of your size. If it is within their expected range then the FIT is paid. If not then I suspect that the FIT may not be paid and you may find that you are investigated.

Good points on the above. Something which I am confused by is why, if you CAN overspec the panels into the inverter why you are not allowed to have more than 4kw worth of panels in the UK.

I have 16 panels of 240W each so I am at 3.84. I asked the installer whether it would be worth adding a 17th (I have loads of roof space) but he said that no, you cannot do it legally
You can have over 4kWp of panels if the inverter output is under 16A but the problem is that they tend to size PV systems on kWp of the panels rather than inverter output. It is an anomoly IMO.

However, the G83 limits are for 16A per phase and so if your inverter outputs more than that then you will be outside the G83 requirements and may need permission from the DNO.

You probably can do it legally if you have that permission, or don't need it, but IMO you would almost certainly lose your FIT payments as the installation would then not be MCS approved and installed from new.
 

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Interesting topic, sounds like above 4kw of panels you can only use a 3.6kw inverter, so local storage becomes more interesting! 8kwp with with 24kwh of storage sounds about right. now where can I find a 24kwh battery.....
 

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Thanks Paul and others :) to be honest for the hassle and the extra output I am not sure it is worth doing it, you might be almost as well to just buy a little grid tie inverter, sling them on the shed roof and go without the extra fit, just use them as a tiny buffer.

I am quite tempted to get a battery mower (my current mower being petrol) couple of panels on the shed roof would be ideal just to charge the mower?

Solar PV is great though isnt it, I have had mine in 10 months and I still love looking at the stats and especially love it when its 100% charging the car, I so should have done it sooner, anyone reading this who hasnt got both an EV and panels, I can thoroughly recommend it :)
 

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Discussion Starter #11 (Edited)
now where can I find a 24kwh battery.....
Lots crashed Leaf's beginning to appear and knowledge about the battery chargers and BMS will be available soon. Prices in the UK are still a little silly but in a few months it will be a viable option :)

If you're in a hurry EVTV are currently selling some older CALB's at less than $1 per Ah :D
 

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Lots crashed Leaf's beginning to appear and knowledge about the battery chargers and BMS will be available soon. Prices in the UK are still a little silly but in a few months it will be a viable option :)

If you're in a hurry EVTV are currently selling some older CALB's at less than $1 per Ah :D
Sadly I'm in a rented house so PV is not on my list right now. We do have solar thermal hot water though!
 

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I don't doubt the veracity of your statement but it means the rules are somewhat nonsensical. Very odd.
I think they are quite sensible!

The FiT is paid out on the basis of a matched system designed and installed by an MCS accredited installer that meets certain standards and criteria (matched panels, suitable inverter etc). It is paid based on a single meter reading and the payments simply based on that reading. By opening it up to make changes it then means that all changes must also meet those criteria and if you were then to complicate the issue by only paying FiT on a fraction of the generated power then starts to become a hugely more complicated scheme to administer and will also open it up to a significant increased risk of fraud.

Even if it were allowed then all changes would need to be made by an MCS accredited installer and the new design would have to meet the design criteria... e.g. a simple case of adding a panel or two (don't forget the panels would need to match!) might then indicate a larger inverter to comply with the MCS requirements so then you are looking at a inverter upgrade.

It could never work if the scheme is to remain simple and easy to administer.
 

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Good points on the above. Something which I am confused by is why, if you CAN overspec the panels into the inverter why you are not allowed to have more than 4kw worth of panels in the UK.

I have 16 panels of 240W each so I am at 3.84. I asked the installer whether it would be worth adding a 17th (I have loads of roof space) but he said that no, you cannot do it legally
I think the limit is 3.68kw which is the G83 certification, anything greater than that is covered by G59 however to achieve the criteria for that you need to have your installation checked by Powergen or somebody like that to see if your supply and local power grid can handle greater than the 16A that your array might stuff up the wires, and I believe a very costly inspection to boot.

Gary
 

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From what I can remember, if your system is over 4kw output, then that puts you in a "commercial" class and drops you FIT rate to a lower price.
 
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