Upgrade to existing 2011 solar panel system?

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We are the lucky owners of a 9 year old system split between SSE and WSW roof. The larger array is on the WSW roof and has issues with shading from a chimney. Having said that the system has been great and paid for itself compliantly last year.
What are you allowed to do with an existing system - presumably not replace the panels with more efficient ones, but can you fit something like solar edge to reduce the effect of the shading?
On a separate note we are relatively heavy power users with an EV and heat pumps Koi pond etc so use the great majority of the energy produced. However we are assumed to export 50% as we don’t have a smart meter. Would we loose out on the assumed export if the metre was upgraded? We do like the idea of charging the car via octopus agile or the like but economically it might not make much sense..
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You can add more panels to your existing system, and even replace panels with more efficient ones, but you'll need to advise the FiT provider (and double check this first before you do anything), and they will then apportion FiT's in the ratio of the original system to the new total. For instance if you have a 4kWp system and add 2kWp more, then they will pay FiT's on the ratio of 4/6ths of what you generate.
You can upgrade to Solaredge under the existing FiT's as you aren't changing the panels, so it's akin to replacing an old or failed inverter with a more efficient modern one, and also something that could have been in place from day one without affecting the subsidy.
Hope that helps.
For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
So for example Scottish Power still can't work out how to implement a website that shows me gas and electricity usage over time based on my smart meter data (which is supposed to be sent daily), they still can't access daily smart meter data to resolve billing issues when I phone them up (asking me to go outside to manually check the meter instead and insisting the meter only sends data quarterly), they still can't work out how to send someone to check or inspect my generation meter which they're supposed to do on a regular basis, last time I checked they still couldn't accept generation meter readings on the tariff change date despite gleefully telling me that this was possible. And then there's the vastly expensive and vastly delayed and shoddily justified smart meter rollout itself. And the government's constant fiddling with what the energy companies are allowed to do, in order to promote an impression of fairness. And the electrification of transport and heating, and the supposedly imminent arrival of the smart self-balancing grid to make it all possible.
Solar Immersion installed May 2013, after two Solar Immersion lasting just over the guarantee period replaced with Solic 200... no problems since.
13 Feb 2020 LUX AC 3600 and 3 X Pylon Tech 3.5 kW batteries added...
You can add solar optimisers to an existing system without impacting your current FIT payments. Instead of fitting solar edge and having to replace your inverter you could look at TIGO optimisers which work with most inverters and you only need to add them to the panels that are actually in shade.
Solar iBoost+ to two immersion heaters on 350L thermal store.
100% composted food waste
Mini orchard planted and vegetable allotment created.
No issues there.
If you have an old spinny meter though, you will lose the fact that it spins backwards when solar panels are doing their thing.
However charging the car on 5p rather than 15p for the last 2 months has been great
4kw sse since 2014 and 6.6kw wsw / ene split since 2019
24kwh leaf, 75Kwh Tesla and Lux 3600 with 20Kwh useable storage
I have a shading issue on my smaller system which "costs" me about 3kWh per day on good sunny, summer days. If you are really generous and say that I lose that amount on 150 days that is only 450kWh per year. At 18p (total FiT rates for that system) that is about £80 per year. The cost of installing anything to combat the shading would be massive - scaffolding, micro inverters or similar, new inverter and labour. Seems unlikely that I would come in under £1,000, maybe more, so the ROI is 12 plus years, by which time the inverter might need replacing again, and so on. I decided to just live with the "mistake" I made when doing the original install.
So, providing original panels (or replacement ones that FIT payer agrees are equivalent) remain, almost anything else can be added - e.g. Solar Edge, more efficient inverter, heavier duty cabling etc etc. But don't take risk of adding new panels to same inverter as old : FIT payer's apportionment of new/old split probably won't agree with your own ! A completely separate system with its own generation meter is by far the best route.
4kWp S Facing 17.5deg slope (dormer roof).
BEV : Nissan Leaf e+
I thought the spinny back meters were illegal... wish I had one LOL
Solar Immersion installed May 2013, after two Solar Immersion lasting just over the guarantee period replaced with Solic 200... no problems since.
13 Feb 2020 LUX AC 3600 and 3 X Pylon Tech 3.5 kW batteries added...
We have been toying with getting a new array fitted + a battery but there is no room on the roof so we would be looking at a set in the paddock- not sure how practical that would be though.. We might try and get some quotes for doing both sets of work and see if it all makes sense.
They're not actually "illegal" and it's the owners responsibility (not customer's) to detect and swap any that act that way. No doubt it's terrific fun trying to decide what a fair correction would be.
4kWp S Facing 17.5deg slope (dormer roof).
BEV : Nissan Leaf e+