Extra solar install, how does export work ?

nologo

I have a 4.6 kW solar roof system installed 3 years ago with a 5kW export permit from the Dno.

Next week a 5.9 kW solar system is going on my roof with separate inverter, by a mcs installer  with a new 5kW dno Permit. It  will have a seperate  generation meter,

I export to Octopus @15p so when my solar is installed ,do I need to inform Octopus ,show mcs paperwork,? I  have a smart meter and 2nd mpan,    TIA

regards   nologo

Petriix

No. Your existing smart meter will measure your cumulative export so Octopus will pay you as normal. 

Reed_Richards

I disagree.  You were accepted onto the Octopus tariff for your existing solar system and would have had to provide them with details of the MCS accreditation.  If you are adding more panels you ought to tell Octopus.

Also, "a new 5kW dno permit" surely just allows you to export 5 kW?  You need a 10 kW DNO permit to cover your total export.

Martyn1981

Hi nologo. Have to say I find that a bit confusing. If it's a second mpan, then isn't it a separate account and a second smart meter too? Hence the 'new' 5kW export, rather than revised up to 10kW?

Reed_Richards

What your DNO is concerned about is the capacity of the wires that supply your dwelling.  If all the exported electricity goes through the same wires then you need DNO permission for the total.

nologo

thanks for all your advice, just to clarify, 
I already had a 5kW export permit,
The new solar install will have an additional permit,
l already have the export mpan from my previous installation, not an additional account..

regards nologo

Martyn1981

Reed_Richards said:

What your DNO is concerned about is the capacity of the wires that supply your dwelling.  If all the exported electricity goes through the same wires then you need DNO permission for the total.

I don't believe that's correct. You'd only need DNO permission for the approved amount per mpan, not the total for the wires.

This may sound like the same thing, but it's akin to neighbouring properties (that share a line upstream) each having a separate export limit. The DNO will need to consider the sum of SSEG's, and export limits approved, but each individual mpan approval/limit would be separate.

[Just a small technicality, but the DNO isn't really concerned about the capacity of the wires, since these are able to cope with far higher import amounts. They are concerned about the local area being able to absorb the theoretical max export from the SSEG / sum of SSEG's.]

Reed_Richards

I still don't think you can have an "additional permit".  If you want to export 10 kW you need a 10 kW permit.  Having two 5 kW permits just lets you export 5 kW. 

Martyn1981

nologo said:

thanks for all your advice, just to clarify, 
I already had a 5kW export permit,
The new solar install will have an additional permit,
l already have the export mpan from my previous installation, not an additional account..

regards nologo

Sorry, but that sounds a bit different to your OP. If it's only one mpan, then Reed Richards concerns seem fully justified, and I'd be thinking/saying exactly the same.

Edit - Ahhhhhhhh do you mean a second mpan by counting the import and export accounts separately? If so, then that's still one connection. I also have an export mpan number, as I assume do all people with registered SSEG's, but my two fully separate PV systems still needed a DNO approval equal to their sum.

Perhaps something is just getting lost in translation here?

Reed_Richards

Even assuming that we can clear up the "translation" issues, I still think Octopus needs to know.  If you have told them that you have a system that can export a maximum 5 kW then that's 5 kWh per hour or 2.5 kWh per half-hourly reading.  So if Octopus start getting half-hourly export readings that frequently exceed 2.5 kWh what do they do?

1. Continue export payments as normal?
2. Limit the export payment for those "anomalous" half hours to the payment for 2.5 kWh?
3. Stop the payments because the system isn't behaving as declared?

I have no idea which it might be but telling Octopus in advance would cover yourself against possibilities 2 or 3.

nologo

thanks again for all your suggestions, I have now emailed 
octopus. to find out..