FIT mystery

[bontwoody]

Im buying a property that has solar panels fitted and receives a FIT payment of about £1500 per year. However Ive been trying to ascertain the actual installation size, but the owner has no knowledge of what it might be.

Externally there are 14 panels facing SW at about 40 degrees inclination. The FIT payment is 60.23p/kWh so that puts the installation date before the 3/3/2012. Internally there is a Fronius inverter which I suspect is an IG 30 from a picture.

On my old house I had polycrystalline panels installed in July 2011 and they were rated at 230W per panel. However if I guess the panels on the new house are the same that comes to 3.22 kWp for the array.

Using this https://re.jrc.ec.europa.eu/pvg_tools/en/ model, if the array was this size then it should produce about 3200 kWh per year (image attached), however looking at the latest FIT statement it only produces about 2400 kWh per year.

To make things even more confusing, I downloaded the FIT installation database. Searching for installations in the area at about the right time I found 24 potential matches. However then I noticed a field called “Accreditation Number” and a reference number on the FIT statement, which looked in the same format.

Searching the database on this number brought back a single entry for a 2.7 kWp system, however the bad news was that it is situated in Bradford!

If anyone can shed any light on what is going on I would be grateful.

A related question I have is can a FIT paying installation be re-sited on the same property without affecting its tariff rate. Im thinking, maybe adjusting its slope or orientation to improve its output?

 

 

[Redbeard]

Hmm... Strange.

 

However:

 

10-12 years ago a fairly well-proven rule-of-thumb assumption was about 750kWh/kWp in propitious conditions. Again another rule of thumb is (was) that you could go to SW or SE with a loss of only 5-10%. Outputs per kWp of what we are getting now (I am not up to date, but 850 - 900kWh seems reasonably common) were not, AFAIK, around then. The sums work for me (within a few kWh) if I assume 240W per panel and a 5% drop-off from due S.

 

As to whether the FIT £ is right for that size of array you could 'unwrap' that figure using RPI for each year going back. If I remember rightly the year 1 FIT was 41.3p, rising to 43 (?.3) in 2011.

[bontwoody]

2 minutes ago, Redbeard said:

Hmm... Strange.

 

However:

 

10-12 years ago a fairly well-proven rule-of-thumb assumption was about 750kWh/kWp in propitious conditions. Again another rule of thumb is (was) that you could go to SW or SE with a loss of only 5-10%. Outputs per kWp of what we are getting now (I am not up to date, but 850 - 900kWh seems reasonably common) were not, AFAIK, around then. The sums work for me (within a few kWh) if I assume 240W per panel and a 5% drop-off from due S.

 

As to whether the FIT £ is right for that size of array you could 'unwrap' that figure using RPI for each year going back. If I remember rightly the year 1 FIT was 41.3p, rising to 43 (?.3) in 2011.

Thanks Redbeard.

Just out of interest I used the same web model for my old house and it was spot on in terms of its annual production which just makes the under performance of the new array even stranger. The only things I can think of are that 1. The panels are of a very low wattage and the array size isnt as big as I think or 2. the inverter is undersized for the array, maybe its an IG 20 and not 30?.

 

Its very odd that the FIT number on the statement does bring back a single entrty in the wrong place. Using my previous skills as an information manager I would be tempted to suspect that the file has become corrupted, which was a common error in the early spreadsheet days when a sort was done on one column without expanding the selection to the whole file. Given the recent cock ups regarding covid data, its easy to see that people in govt are still using early versions of excel.

 

Any ideas on the re-siting of panels, its seems no worse than cleaning them to me. 🙂

 

 

 

[joth]

1 hour ago, bontwoody said:

looking at the latest FIT statement it only produces about 2400 kWh per year.

Don't rule out something silly like the inverter got switched off for a few weeks or something. Happened to me! Electrician shut it down and I hadn't realised.

 

 

 

Also it could be after 10years there's a fault in one panel making a whole string under perform.

 

 

 

I think you can even replace panels and retain original fit, so long as you replace with like for like? I'm no expert tho

[bontwoody]

1 minute ago, joth said:

Don't rule out something silly like the inverter got switched off for a few weeks or something. Happened to me! Electrician shut it down and I hadn't realised.

 

 

 

Also it could be after 10years there's a fault in one panel making a whole string under perform.

 

 

 

I think you can even replace panels and retain original fit, so long as you replace with like for like? I'm no expert tho

Hi Joth. I got to 2400 kwh pa figure by taking the total production since it was installed and dividing it by years so its an average over its life, so the switched off inverter theory wont work. A faulty panel would though if it happened a long time ago! Yes, the like for like replacement is OK. Its interesting that if the array was over-producing then you would be inspected by the FIT authorities to see why, no such luck if its under producing 🙂

[ProDave]

Just a few random thoughts.

 

If you are buying the house, make SURE it is written into the contract that the FIT will be assigned to you on completion.

 

The actual power generated will depend on lots of things, if there is any shading from trees, your or neighbours roof, even a chimney pot or dormer window can create shading and reduce the output.

 

When you can, look at the inverter in the middle of a sunny day, it will tell you how much power it is generating.

 

And last random thought, has the owner been submitting readings quarterly, or have they been estimated?

[bontwoody]

1 hour ago, ProDave said:

Just a few random thoughts.

 

If you are buying the house, make SURE it is written into the contract that the FIT will be assigned to you on completion.

 

The actual power generated will depend on lots of things, if there is any shading from trees, your or neighbours roof, even a chimney pot or dormer window can create shading and reduce the output.

 

When you can, look at the inverter in the middle of a sunny day, it will tell you how much power it is generating.

 

And last random thought, has the owner been submitting readings quarterly, or have they been estimated?

Hi Dave, yes, Ive already stressed to my solicitor about the FIT payment as when I sold mine there was no check at all. In the end I did it myself but if I hadnt who knows how long it would have taken to sort out.

There arent any shading issues and the roof slope and orientation are included in the model used. Im eager to get in and have a look whats happening, it looks like the meter has been read and submitted. My last FIT provider insisted on a visit or photo of the meter every year so I dont think the total generated can be very far out.

[bontwoody]

Update for the benefit of anyone else looking at the FIT database. I was using the wrong ID field to search. The correct field to search is FIT ID not Accreditation number. This brought back the correct installation, a 2.66 kWp one situation in the correct geographical area 🙂