FIT meter gives strange readings; installer gone bust!

Qyburn

Reed_Richards said:

@Qyburn, I've been searching for this Ofgem statement you refer to in the document you referenced and I haven't found it.  Can you please tell me which paragraph I have to look at?

Page 32 3.27

"3.27. FIT installation owners considering installing a “bi-directional meter(s)” should 

note that FIT meter readings taken using such meters will be calculated by the 

meter on the difference between each month’s import and export readings. This 

differs from the meter readings taken by standard meters, which measure and 

record the generation and/or export of the FIT installation on a cumulative basis. 

If the difference between import and export in one month is negative, zero FITs 

payments could be claimed. "

Reed_Richards

Qyburn said:

Reed_Richards said:

@Qyburn, I've been searching for this Ofgem statement you refer to in the document you referenced and I haven't found it.  Can you please tell me which paragraph I have to look at?

Page 32 3.27

"3.27. FIT installation owners considering installing a “bi-directional meter(s)” should 

note that FIT meter readings taken using such meters will be calculated by the 

meter on the difference between each month’s import and export readings. This 

differs from the meter readings taken by standard meters, which measure and 

record the generation and/or export of the FIT installation on a cumulative basis. 

If the difference between import and export in one month is negative, zero FITs 

payments could be claimed. "

In my opinion that says nothing about which way round the meter should be fitted, provided that you can identify which reading is import and which is export (which is trivially easy to do).  But I think we may have to agree to differ on this point.

Edit: In fact the conventional meaning of "the difference between a and b" is a - b?  So that would be import minus export which you would expect to be negative.    

In practical terms it is usually very difficult to achieve a nett negative reading, even during a single day.  If you charge and discharge the battery through a bidirectional meter then battery losses will cause the export to be slightly less than the import.  But on even the darkest day in winter it is almost certain that the export from the solar panels will exceed any battery losses so the nett of export minus import will be positive.  For this to happen over a month is well nigh impossible and I have never encountered a FIT scheme that asks for readings more frequently than once per quarter.            

brianwdcck

I've been following the various comments in relation to the bi-directional meters and I have a different perspective and I'm currently challenging the opinion from the licensee and installer of my revised system. My solar panels were installed in 2012 and we have a high FIT tariff. Last year we needed a new inverter and took the opportunity to install 2 batteries at the same time. The installer said that he was obliged to install a bi-directional meter which has recently resulted in a negative reading. Under my FIT arrangement, payments are based on gross PV generation, with export treated on a deemed basis rather than being measured. It is my contention that the use of a bi-directional meter is non-compliant in such a situation as it cannot record gross PV generation and the net figure which is being requested is erroneous since measured export to the grid is of no consequence. It is my view that the FIT regulations are being mis-applied by requiring or relying on a net generation figure. Two different members of the FIT team from the licensee have acknowledged that they do not know why my reading represents a negative figure but have assumed that it has something to do with battery charging. One has indicated that my previous payment was an overpayment and the other has suggested that future payments will not be made until my net reading has exceeded the previous reading which will require approx. 200kwh of PV generation to do so.

I'd be interested to know if anyone else has challenged this and what the outcome has been.

brianwdcck

In relation to my previous comment would also comment on previous responses @Reed_Richards and @Qyburn

Citing para 3.27 is reasonable and the paragraph is accurate but caution should be exercised and it’s important to read it in context.

Paragraph 3.27 is descriptive rather than prescriptive. It explains how bi-directional meters behave and explicitly warns of the consequences of using them under FIT. Ofgem is not stating that bi-directional meters are required or that this is the correct way FIT should operate; it is highlighting that such meters calculate a monthly net difference and therefore can result in zero FIT payment even when PV generation has actually occurred.

The key sentence in the quoted section is often overlooked: Ofgem explicitly contrasts bi-directional meters with standard FIT generation meters, which “measure and record the generation … on a cumulative basis.” That cumulative, forward-only behaviour is the core design of FIT generation payments.

In other words, paragraph 3.27 is a warning: if a generator chooses a bi-directional/net meter, genuine PV generation may go unpaid in some periods. It does not say this approach is required, preferred, or compliant in all cases — only that this is what will happen if such a meter is used.

Later Ofgem guidance (on co-located storage) makes the primary rule explicit: the FIT licensee must be satisfied that the generation meter only measures electricity generated by the FIT installation and not from other sources. A meter that subtracts grid import and can run backwards struggles to meet that test. It is clear that a bi-directional meter, by its very nature, is influenced by electricity from sources other than the PV production. FIT payments are not made on the basis of the generation of surplus energy.

So paragraph 3.27 doesn’t undermine FIT’s generation-based design — it actually explains why net metering can disadvantage FIT generators, which is exactly the issue being discussed here.

QrizB

brianwdcck said:

Last year we needed a new inverter and took the opportunity to install 2 batteries at the same time.

It has long been recommended on this forum that you shouldn't mess about with a FIT-qualifying PV system without a proper consideration of the potential consequences. Your experience is what was feared.

brianwdcck said:

I'd be interested to know if anyone else has challenged this and what the outcome has been.

Your problem, of course, is that you no longer have a record of your gross FIT generation.

One way out of your situation would be to add a generation-only inverter for your panels and demote your current hybrid inverter to serving as an AC-coupled battery storage inverter. You could then install a new generation-only meter on the generation inverter and you'll be back to where you began, albeit having "lost" records of a year's generation.

brianwdcck

Thanks for your comments @QrizB - I had no alternative but to add a new inverter as the old one wasn't working properly but I used a fully qualified, register installer and my licensee signed off the install. The key problem is that they seem to believe that a bi-directional meter is mandatory. I will continue with my 'case' and will take it to the ombudsman for a resolution. It is clear that their current logic is flawed.

I understand that a more simple solution is to install a PV generation meter rather than a new inverter but my current argument is that the installation is non-compliant in terms of the FIT regulations and I'm shocked that my licensee does not seem to understand this. The snag that I see in your solution is that if my licensee doesn't agree with the potential solution they will not accept the readings and so I don't see any other solution that getting them to agree to a new compliant system. Many thanks.

Qyburn

brianwdcck said:

I understand that a more simple solution is to install a PV generation meter ..

The problem is that with your current installation there's nowhere to install a meter that will only record generation and not battery discharge.

Could you give a schematic, or a more detailed description of your current set up, in terms of the net meter? Properly installed it's "export" register should count anything coming out of your inverter, not specifically grid export.