[Indyk_EONNext]

Hey @GSV3MiaC

How are you?

Thank you for reaching out via our forum and sharing your data. 😊

Now I am just looking into your query for further clarification, regarding whether SEG payments can be paid if you are exporting more than your MCS estimated generation, as this is something that is stated in our T&Cs.

[Lee_EONNext]

@GSV3MiaC Hey

Thank you for the detailed post, its amazing to see you tracking the data, this is something when I worked in the FIT Team and worked applications I would always advise generators to keep a log, diary or spreadsheet. This way you can track what's going on. This is great if your system stops working as you can see this right away! 👏

So, onto payments, can I ask who has advised that we pay or would pay to the MCS estimated annual generation? I will touch on both FIT & SEG in terms of how payments are made and when we may use an estimate, all of this is on our T&Cs for both FIT & SEG

It's important to remember here that FIT & SEG are different albeit solar 😎

So in FIT as you're probably aware, we pay Generation and a type of export, usually Deemed. You can opt out of deemed and apply for SEG. In FIT we pay to the generation meter read, never the inverter or any other device, always the generation meter. The only time we estimate the reads in FIT is if you don't supply a March 31st read for the change of tariff.

SEG - This is export only, no generation payment, we pay again to the export read from the smart meter to which the customer supplies. We never pay estimated reads on request or just to make a payment. There are occasions where we might need an estimate read however this is something we discuss case by case and is not a written rule as such.

The number of units exported for SEG should never be more than your system's optimal generation as this would potentially mean your system is actually bigger than whats actually installed on the paperwork. Just to clarify, the optimal generation is not the same as the estimated annual generation. In the 8 years of working in FIT and pretty much all of the processes, I have only ever seen 5 systems exceed optimal generation, conditions need to be perfect for this. We need to remember that Generation and Export are not the same thing, I would expect some units to be used in home.

The MCS is purely used as a measure to what we would expect a system to actually generate, again this EAG (estimated annual generation) is estimated by your installer based on your install, you could have two systems, both 4kw and the EAG's be different. There are so many variables to consider.

When do we use the EAG?

When a FIT payment fails tolerance and the read we are trying to pay exceeds an 'average per day' if we work out the average per day and this would is more than the estimated annual generation, we would ask some questions.

Nothing too heavy, just things like,

Has there been any changes to the system?
Any trees cut down blocking the solar?
An inverter change? as these typically last 7 years ish, new inverters are more efficient and therefore these mess with the system tolerances etc.

Lots of factors to consider. I just wanted to hop on and hopefully this clears things up, I am curious to who has mentioned about paying to estimates though?

If anyone has any questions about this feel free to respond to the thread and I will reply on my return, as I am on leave until Monday.

Thank you

[GSV3MiaC]

There is this debate from (some) E.on support staff about whether SEG can be paid if you are exporting more than your MCS estimated generation.

Just to add to the export vs mcs estimate debate, here is some actual data from my first (FIT registered) array, as recorded by my inverter and tracked by a nerd (me) over many years. As you can see the MCS 'cautious, don't oversell' estimate is way lower than my average, which is just slightly better than the PVGIS estimate, which itself got thrashed in 2022.



Attempts to limit SEG payments to X% of MCS estimate are hopeless, unless X is about 125%.

[GSV3MiaC]

I have seen emails supposedly from your SEG folks querying SEG payments based on the export being more than the MCS estimates. Not sure where you get 'optimal generation' numbers from, please show your working, given mcs paperwork only shows kWp(eak) and the (pessimistic) estimated annual generation.

I did not mean you pay mcs estimates, just that there is an opinion that THAT is what you use as an upper limit somehow.

You can find a lot of discussion about it, along with the emails, on the Facebook group (worth a visit)

https://www.facebook.com/groups/1173953470447091

[Lee_EONNext]

@GSV3MiaC Thank you for the reply, I wouldn't be able to look on that link i'm afraid due to access, we don't use Facebook unfortunately.

Without seeing people accounts etc, it's really tough to advise however in terms of a blanket response, here we go......

The MCS estimate is for generation, not export, if memory serves, there is no estimated export on the MCS? Please let me know if that has changed.

if your system was to exceed the estimated annual generation, in terms of SEG - The team would of course use this figure for data purposes, as SEG is export only and not generation.

People are of course entitled to opinions and of course we fully respect and encourage people to share those on the Community. Something to consider is the full picture, without customer accounts, data, reads and export meter photos, It's really tough to really give you a super detailed answer, as the person or persons in question could have had upgrades? new meter installed? a new inverter? the list goes on.

I think it's really important to consider all the variables here and that I would be very surprised is a solar system exported more than the estimated annual generation, that's my opinion and I am not saying that this would be impossible. Is it something I have seen? No its not, however I will do my best to ask around and find out.

Generation and Export are two different things, It's really important that this is highlighted. You could generate 100 units and export 0 - You can't export 100 units and generate less then 99 units, unless you have a battery and charge from the grid to then export, lets not go down that rabbit hole.

in terms of FIT and optimal generation, I would recommend taking a look at the Guidance and as soon as I am back from leave I will see if I am able to share the calculation with you, It's been a while since I have had to use it and this is why it's escaped my memory, however I will find out and let you know. If you want to look at the guidance and want to discuss that with me, by all means I am more than happy too.

However, back to SEG and the EAG on the MCS, let me find out the read validation process for SEG reads that exceed the EAG or fail tolerance. I am currently off at the moment so this could possibly be after the weekend.

Thanks

[GSV3MiaC]

Thanks Lee, sorry you can't get to Facebook, there are a lot of useful comments there. Anyway, have a good vacation (or at least absence from work). Here is a sample, for those who can't or won't do antisocial media.

If valid, the Eon sender needs educating about power (kW) vs energy (kWh, joules).

I think my query boils down to "Where does the EAG come from" (how calculated). The mcs certificate estimate of kWh is, by law and custom, pessimistic. The mcs peak power is (by DNO requirement) close to spot on, but you have to multiply that by local sunshine (well, insolation) data to get generated energy (which is what pvgis does, and what mcs installers do using very pessimistic numbers).

So if I have 6kW of panels on a 5kW inverter at location x, pointed in direction y, at inclination z, what do eon think the EAG is? . No, not the MCS kWh number, we know that will always be low, or else they would be liable for misspelling. The MCS Estimate is good as a lower bound, but that's about all.

[DebF_EONNext]

Originally Posted by Lee_EONNext

Lots of factors to consider. I just wanted to hop on and hopefully this clears things up, I am curious to who has mentioned about paying to estimates though?

If anyone has any questions about this feel free to respond to the thread and I will reply on my return, as I am on leave until Monday.

We see you 👀 @Lee_EONNext 🤨 get that screen closed and enjoy your well deserved break 🍸🏖🌞🥩🏋️‍♂️ the community will still be here on Monday 💚

@GSV3MiaC you've asked some interesting questions and when Lee is back he will have a proper look into this for you and hopefully be able to give you more clarity on your follow ups. I'm not even going to pretend to know the answers as this is well above my head and I'm still learning about it all. I love that the community has this space for open and honest discussion if it's helping me learn new things then it will no doubt help lots of others too!

[GSV3MiaC]

@DebF_EONNext fwiw, I raised the issue with my installer (a Which Trusted trader, used by mylocal council and others) and the reply I got back to the query 'why are MCS estimated Annual Generation numbers so low compared to reality?' was

"When we predict the output of a system we have to use the MCS calculation which combines pitch/orientation, shading value, irradiation, and there is also a 20% degradation of the panels (based over 20 years) worked into this. We are not allowed to include the benefit of having better quality panels (i.e N-type silicone, high efficiency), or the extra performance you will get form having the panels individually optimised so the system should always do a little better than we are allowed to predict."

So basically the MCS EAG will always be below reality (I have yet to find anyone who claims their system does worse than MCS estimate, unless it is broken). PVGIS (latest version) is closer to reality, but there is still a big variance based on weather.

I actually have DAILY data for the first (FIT) array, to go with the monthly summary numbers upthread. As you can see the variance is huge!

[Lee_EONNext]

@GSV3MiaC Thank you, and thank you for the screen shots, it really helps.

So in this case, its looks like optimal has been used in terms of 'what your MCS states it can generate'

We always go by the TIC & DNC - First we ask if there are any changes to the system like more panels added, cleaned them etc or discharging from the battery which makes it look more than it should, which does happen. It mentions later in that email about the Total installed capacity which is what we use.

In terms of your EAG that's down to the installer and not something we would set or have any control of, which is why we use the TIC (total installed capacity) as this number should be the total installed and is based on fact not an estimate.

Just going back to EAG, I would potentially not worry too much about it, its the same when you do a new quote for energy, it's potentially an estimate and is not accurate, it's just a base guide. Lets say for your fit payment this quarter, your read was high, we would work out the average per day for the quarter, and is this was below the EAG for the year, we would potentially just pass the read (providing there has been no changes that affect eligibility)

I often wonder if the installer undershoots the EAG to cover themselves? however again understanding its an estimate, based on similar installs in the area maybe? roof location and all the other variables?

If it was higher, we would use the TIC max figure. Also the EAG does it take into fact of degradation 10% yearly? looking at your system might not be happening.

Your total installed is it 5kw as mentioned? If so I don't think you have anything to worry or be concerned about, the query above that you have also shared, I think there might be some confusion around EAG and what we actually use and that's the TIC.

I would be interested to see how the customer is getting on, shame we can't check in with them.