Expanding Existing Solar System and adding battery and keeping fits payments
madwayne
Forumite 14 Posts
So I currently have a 2KW system, had it about 7 years and was one of the last to get fits payments.
I know that the system at times generates more than we use during the day.
So adding a battery makes some kind of sense if it generates enough, however the inverter isn't capable of DC coupled charging (which means the less efficient route of ac coupled would apply.
AC coupled charging is usually cheaper than dc coupled if I understand correctly but not as efficent.
However I want to add additional solar panels say 2KW to the back of the house efficiency alleged isn't a million miles from the front but it is slightly less, not a big issue.
Over the years of my current system i have noticed there is sun on the back most of the day and it certainly starts earlier because of the orientation of the roof.
Also noted as you would with the English weather that some days start bad and some days finish bad with sunlight/ cloud cover. So expecting that there could be some unexpected gains some days.
original system:- 2KW inverter generation meter
additional system 2KW panels, new inverter generation and maybe export meter,
Would like to hear from anyone that has expanded their system and not had fits payments affected.
Obviously i cant have fits on the new additional panels, but they could be used for charging a battery.
Ways of achieving this:-
new inverter 4KW accepting 2 panel arrays :- existing and new
generation meter for first and second array
DC or AC coupled battery storage
Export meter for second array of panel (at least until fits expiry 2035)
or :
exiting 2 KW system
generation meter
ac coupled battery storage
new system standalone 2KW
generation meter
export meter
ac or dc coupled battery storage
not sure if easier to have two ac charging into battery, or what options are available,
I know that the system at times generates more than we use during the day.
So adding a battery makes some kind of sense if it generates enough, however the inverter isn't capable of DC coupled charging (which means the less efficient route of ac coupled would apply.
AC coupled charging is usually cheaper than dc coupled if I understand correctly but not as efficent.
However I want to add additional solar panels say 2KW to the back of the house efficiency alleged isn't a million miles from the front but it is slightly less, not a big issue.
Over the years of my current system i have noticed there is sun on the back most of the day and it certainly starts earlier because of the orientation of the roof.
Also noted as you would with the English weather that some days start bad and some days finish bad with sunlight/ cloud cover. So expecting that there could be some unexpected gains some days.
original system:- 2KW inverter generation meter
additional system 2KW panels, new inverter generation and maybe export meter,
Would like to hear from anyone that has expanded their system and not had fits payments affected.
Obviously i cant have fits on the new additional panels, but they could be used for charging a battery.
Ways of achieving this:-
new inverter 4KW accepting 2 panel arrays :- existing and new
generation meter for first and second array
DC or AC coupled battery storage
Export meter for second array of panel (at least until fits expiry 2035)
or :
exiting 2 KW system
generation meter
ac coupled battery storage
new system standalone 2KW
generation meter
export meter
ac or dc coupled battery storage
not sure if easier to have two ac charging into battery, or what options are available,
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Re your plan - I think if you get more panels at the same time as battery then you benefit form the battery being zero VAT whereas otherwise it is standard 20%
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:
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.
OFGEM is also not that helpful, they state:
No.
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
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!!!!!
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.
For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
1. if inverter capacity goes over 3.68kW in total you will need DNO approval. You appear to have a 2kW inverter with 2kW of panels. This isn't the best way to spec up a system. You are generally better off with an inverter which will cope with about 75-80% of peak output.
2. The fact that a 4kW E/W will never go over the 3.68kW figure because of the spread, makes no difference. You house max is 3.68kW period.
3. I don't know if it has changed but a battery without a PV system used to incur full VAT @ 20% whereas with PV it's only 5%. When I got my battery the extra panels essentially were the same cost as the VAT on the battery so this by far the best decision.
4. When I added the battery and the extra couple of panels I didn't think it would ever pay back the costs - now I think there is a fair chance that it will!
Install 2: Sept 19, 600W SSE
Solax 6.3kWh battery
2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 2.5kw inverter. 28MWh generated, long-term average 2.6 Os.
(Currently am going down the V2H route, purchasing a second EV for 6.5k to be a 14kwh battery as it seems cost comparable and is very flexible but this might tip me back to extra panels and a battery. I have gone for a 5 hours at 4.5p tariff and scored a used ASHP so am hoping that with a decent amount of battery storage my utility bill may go from 6-7k post the October cap increase to something vaguely more affordable)
Currently on fits with EDF.
EDF have said that I can make the system larger, however can’t have the extra on fits, which is fair enough. Haven’t said how the fits would be calculated.
my concern is how the systems are separated.
if like that the pro rata is applied this likely to lead to a change in fits payments, larger or smaller no idea. Let’s face it that all depends how much the panels are maxed out and all have seen clear sky performance compared to cloudy.
At the time I had the solar panels fitted I was in two minds of split roof and didn’t have the spare cash, only 3k at the time but to have the back as well was nearly £7000. No one was really doing batteries back then.
with 13 years fits left I certainly don’t want to lose that.
Prices for 2kw adding as a new system isn’t that different to those costs, the battery is where the costs become more but rising cost of electric, but calculating the battery size required and space it takes up.
think unit prices were about 14p in 2015 and now at 28p so buying in, but don’t quote me on that.
certainly don’t see why aseperate 2kw system should allow export with export meter but how that works is another matter. Looking SEG
wrt to charging via ac, certainly it be better for front to charge up battery after generation and before the new system exports…. But can’t have it all ways.
given the front generates excess now clear skies and excluding high powered devices, it possible the back would also generate excess.
Indeed think the information out there isn’t very clear for this kind of thing.
how do you work out what size battery is the best for you?
I will look at getting clarifications on the points raised above.
1. Advice from my installer on adding to the system was that there are no guarantees from the FIT provider. Indeed they may well change their mind once the system has been altered. At this stage there's no going back and the FIT will be lost. They hadn't come across anyone who had got a clear answer to the pro rata question so the advice was don't try to go there. Note Martyn did not say that you can apportion merely to check that the FIT provider is prepared to do this.
2. To go above 3.68kW you need to apply to the DNO. They charge for this ( a few hundred pounds?) and there is no guarantee that they will agree.
3. Battery size is a tough one. Ideally one large enough to get you through a winter's day, if you fill it up overnight on an off peak tariff (e.g. Octopus Go if you have an EV). At this time of year much of the capacity is wasted. You may not need all you generate (may be on a good day as much 20kWh from a 4kW system) so there's no point in storing it all. Also be aware that batteries will only discharge at quite low rates. Mine is set to discharge at 2.5kW max. So even if I have enough power stored if I have more than one energy sapping appliance on at once (oven, toaster, kettle, washing machine (as it fills), dishwasher (when filling or rinsing)) then I'm still importing from the grid. Ideally you'll need to get a good handle on daily usage to decide how big to go and then form a judgement on how much to spend. My 6.3kWh battery does well at this time of year but falls pretty short in autumn and early spring. I've considered increasing it which would avoid paying for peak time electricity altogether but would never cover its costs.
Install 2: Sept 19, 600W SSE
Solax 6.3kWh battery
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:
No.
For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
the 3.6kw limit I am seeing mixed information, going back to fits over 4k and less than 10kw and now not an issue…….
Think the plan has to be have a proposed system and get approval on that before commitment.
useage being looking at that today and it’s relatively low and not drawing much if anything from the grid even though cloudy and solar output is low. The extra panels would allow for these poor days and charge the battery up. Don’t think there would have been much scope to charge a battery today given how cloudy it’s been all day.
I am reluctant to change the original system other than battery. Ie upgrading panels, to be fair having looked at the panels power and sizes don’t think it be worth swapping any anyway.
if the back we get the same I be happy but maybe able to get more with fewer panels and higher W but the price may influence that decision but 7 400W panels is a big jump from 7 300W panels but the sizes are similar but not the same. Even 6 panels would be a jump up in power.