increasing solar array - worth it?

[kuruma]

So, for a quote of £4995 from a company we've used before, we could get another 5.2kW array set up on our north-facing roof to complement the 5.2 we've got on the south side. This is estimated to generate 2,900 kWh annually. Our current energy needs mean we buy in about 6500 kWh a year almost all of it on IO's off-peak rate of (soon-to-be) 7p as we run the house off the powerwall during peak hours. The new array would thus save us about £200 annually at that price because we can charge the powerwall off the solar instead of off-peak electricity. On sunnier days, it would also contribute to our FiT which currently earns us £300 although I'm not entirely sure how to estimate exactly how much it would contribute. If I disregard the FiT income, at £200 a year, it would take 25 years to pay off the £5k it would cost us to install it. We have the cash to spend on this, but to me, this doesn't really seem worth it.

In addition to the long repayment time, I'm concerned about having the entire roof covered in solar panels. If there's ever an issue up there, e.g. we lose a ridge tile in a storm, it's going to be tricky to get a roofer up there to do any work.

I might have missed something so I'm laying my thoughts out here to see if the hive mind agree that this probably isn't worth our while.

 

[Jason71]

At £200 pa no. But I am confused. Octopus fixed export is 15p per KWh so surely the minimum price your 2900kwh is worth is £435.if some turns out to replace full price electrons maybe a bit more. Why would you charge batteries from electricity worth 15p when you can do it overnight for 7p?
The 15p could fall of course in future.

 

[kuruma]

Firstly because for half the year there isn't enough solar to charge the pw so we do it at night. Secondly we're on FiT which is guaranteed about 6p export forever. Not surrendering that for an export tariff which could disappear at any point. Does that make sense?

 

[AndrewGR]

Doesn’t the FIT tariff contract (which I admit I have failed to find) limit you to replacing failed components - and in any case, limit to 4kWp for domestic installations?

 

[Drew57]

The new array would thus save us about £200 annually at that price because we can charge the powerwall off the solar instead of off-peak electricity. On sunnier days, it would also contribute to our FiT which currently earns us £300 although I'm not entirely sure how to estimate exactly how much it would contribute.

FIT only pays against your pre-existing array as it was when you registered - your FIT provider will have a record of your average generation by quarter as well as the expected average for your location/orientation etc so any additional panels will throw up a discrepancy which will be challenged.

Permission must be sought before adding panels and then your FIT provider will need to make an adjustment against payments (I know this because when I added panels some years ago the whole process was basically a nightmare for 9 months even though I HAD sought permission and it was agreed. After that I made sure that a second array was entirely separate and not recorded by the FIT meter).

 

[kuruma]

In the last year, I've added the extra array we put on the south-facing extension to the FiT via Octopus. It's on a separate inverter. It was really simple to do so I assumed adding in a further array woudn't be an issue. However, you've just reminded me that I've actually forgotten to report the extra array since adding it!

 

[kuruma]

limit you to replacing failed components

Do you mean that if something fails we can't replace it? Sorry, just not sure.

As for export rates, here's the latest statement. You'll see that it ranges from 5 to 7.14p/kWh so I gave an average of 6 above.

 

[AndrewGR]

I understand that if you are receiving payments under a FIT contract you are allowed to replace failed components, a dud panel, or inverter for example. But that you can’t increase the output of the system by adding panels. I’ve looked for a copy of the contract either online or in the documentation that came with my own system but failed to find it. I’ve been looking because a friend has a problem with his system - water getting into connections between panels I think, and one supplier is encouraging him to replace all his panels with ones with a higher output. Neither of us know whether this is allowed.

When considering the difference between the Octopus outgoing 15p tariff and the FIT 6p tariff you have to note that you are only paid the FIT export rate on 50% of what you generate but you would be paid the Octopus rate on 100% of your export. When I got a smart meter ((but before I got batteries or an EV) it confirmed what I had suspected - that I was actually exporting about 80% of my generation. I applied for the export tariff in April - I’m still waiting. On this occasion Octopus have let me down - usually they have been very efficient - and it looks like I will miss the ‘peak export season’ this year.

 

[kuruma]

Ok thanks everyone... Very interesting. Looks like it's worth me talking to octopus to see what the limits might be.

 

[MrBadger]

Also remember with FiT the array limits that affects payment rates. It’s the reason why most FiT based arrays were <4kWp. The moment you tipped that, FiT rates were slashed to the point that iirc doubling array size would pay less than the original FiT rate.

I just checked my 2013 rates. It’s not as drastic as I remembered, although would have been when I was considering a >4kWp install.

Higher rate <4kWp 14.9p
Higher rate 4-10kWp 13.5p

Above is in addition to the (50% deemed) export tariff at 4.64

Whilst this difference was enough for me to leave a panel out of the array, contrary to my original thoughts it wouldn’t significantly affect a much larger array.

 

[Dilly]

@kuruma Are you sure that you are being paid under the FIT scheme.
The rates for feed in and export change in April each year and remain at that level for 12 months.
That looks more like Small Export Grant to me. Unless of course the rules changed as FIT ended.
The current FIT scheme export payment is 6.79p/kWh and will remain in being until April 2025.

I have two independent sets of panels; the first from 2015 under the FIT scheme. The second from 2020 which cannot export.

 

[kuruma]

Absolutely it's FiT. Panels installed in late 2018. Feed in Tariff payments eligible from Nov 2018 with Good Energy. Switched to Octopus Dec 2020. Here's proof with historic export figures from 2020:

 

[MrBadger]

Curious why your switch rates were less than current rate. FiT payments only increase until end of plan 20/25 years and should be determined by standard FiT tarrif.

Sounds like new FiT payers are taking a cut? No need to actually change FiT provider - I’ve never had energy supplied by mine. I chose them because they were said to be reliable quick payers - which indeed they were.

 

[Dilly]

Absolutely it's FiT. Panels installed in late 2018. Feed in Tariff payments eligible from Nov 2018 with Good Energy. Switched to Octopus Dec 2020. Here's proof with historic export figures from 2020:

View attachment 1060539

That’s odd. Scheme must have changed later on.

 

[Drew57]

My original FIT was a 4kW array and I wanted to add a further 1kW.

British Gas were my FIT provider and my installer was advised by the DNO that we must obtain BG permission as payments can only be made against the original 4kW.

BG replied that this was permissable to go ahead (with copies of all documentation from my installer) but payment could only be made against the original 4kW array, therefore all calculations for payment would be based on 4/5ths.

That worked well until BG moved their IT systems over to SAP at which point my account suddenly merged with a nearby neighbour and I had three Installation IDs - the original 4kW array, a new 5kW array and a further 12.5kW array all with different Installation reference numbers and Generation MPANs. This meant I received no payments for the 9 months it took for me to fight with various clueless overseas call centres & at one point I was asked to refund the combined total of both mine and my neighbours FIT excess (4kW 'correct payment' minus the total of the new 1kW and a further 12.5kW, more than I had ever received). Each time I spoke with BG (which was a lot) they would say my account was blocked and would quote a different one of the three IDs.

Eventually I found the most helpful and professional Customer focused individual I have ever interacted with (Claire Butlin BG UK) - she worked to unravel this and contacted me tirelessly for months, during weekends, her holiday, many evenings until it was finally resolved. Every call was ended by a promise to call me at a certain time on a future day and she never once failed to do this. "Outstanding" doesn't even come close to the commitment of this individual and is the reason my FIT remains with BG.

Ever since then, I submit a quarterly summary online when prompted and payment into our Bank account happens usually within 2-3 working days. This equals 4/5ths of what the 5kW array generates and a further 50% of that for deemed export.

(...at a later date I made sure that the inverter for a further 2.5kW array was installed against the house load via the consumer unit so this has no bearing on FIT or car charging. Sadly there is no way to measure or separate export from these panels plus the 1kW in a way that would allow Octopus to pay against SEG or any other scheme).

Anyone still on the FIT scheme needs to be transparent with the payment provider and as @AndrewGR mentions - only replacement like-for-like is permitted, not addition unless with permission and that part will not receive any FIT payments.

 

[kuruma]

No need to actually change FiT provider

Oh there def was. Good energy were anything but... And have now gone under anyway.