Problem with DNC for signing up to Octupus for solar payments

I have been trying to set up the excess solar generation output with Octopus, to get a little bit of money back from the stuff we don't manage to use in the summer months, and Octopus have thrown it back at us with

"...have received a rejection from your DNO as they have been notified of a Declared Net Capacity (DNC) different to the one on the MCS certificate"

I believe Western Power are in charge of distribution in our area.

The original suppliers (Cisco Homes) have, in just the last month or so, gone into liquidation, so we can't go through them to have the certificate corrected. The MCS site states that we can apply directly to have it corrected but the problem is that I have no idea what is supposed to be corrected.

The installation consists of 17 x 405W panels feeding a Solis S5-EH1P5K-L hybrid inverter, with 4 x 5kW FOX ESS LV5200 batteries.

Having inspected the MCS certificate, the total installed capacity is listed as 6.88kW, whilst the Declared Net Capacity is listed as 5.50 kW

As I understand it, the inverter is capable of momentary peaks of 5.5kW output so I assume this is why this figure has been declared as the DNC, so is it as simple a case as requesting the DNC be set to the same as the TIC, 6.88kW? I can't seem to find a definitive answer and I want to get it right first time.

Thanks in advance,


  • As a follow up to this, and to move to a new question as a result, I've heard back from Western Power to show that they approved our installation based on the installers quoting 3.68kW export, so this explains the discrepancy. Western Power have, however, confirmed that there is no problem with our system exporting 5.5kW (though 5.5 would be brief, the inverter can only do 5kW sustained) and we "just" need to find a new supplier who can fill in the appropriate forms to correct the value.

    I presume we need to find a competent, registered, solar installer to do this?

    I am aware that this isn't going to be free, but the additional export return from the extra 1.4kW, will pay for this in no time.

    Thanks again
  • QrizB
    QrizB Posts: 13,634
    First Post First Anniversary Photogenic Name Dropper
    Cluckers said:
    I presume we need to find a competent, registered, solar installer to do this?
    In your first post, you said that you could apply direct to MCS?
    Alternatively, your defunct installer will have been part of a consumer code (HIES, for example). You could ask them for help to sort this out.

    N. Hampshire, he/him. Octopus Go elec & Tracker gas / Shell BB / Lyca mobi. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 30MWh generated, long-term average 2.6 Os.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs.
  • The MCS part was based on correcting whatever mistake was on there. It turns out the mistake was on the DNO the defunct installer applied for - they took the easy "no questions asked" 16A application, which limits us to 3.7kW output, but if they'd just asked Western Power then they would have known that they could have applied for the full export level the inverter is capable of, which is what they put on the MCS certificate. As per my follow-up, Western Power have confirmed in writing to me that there is no problem with grid capacity for us to export at the full rate.

    I will try and find out which body they belonged to from the documentation we have, thanks for that suggestion :smile:
  • michaels
    michaels Posts: 27,874
    Photogenic Name Dropper First Anniversary First Post
    Fingers crossed Western Power Networks are as good as their word - you would be royally screwed if they came back and said no export over 3.68kw and you have no comeback against the defunct installer!

    You may start finding out way more than you ever wanted about the differences between G98, G99 and G100....
    I think....
  • Not sure where my previous attempt to reply went (probably finger trouble on my part) but the HIES suggestion was perfect. Had a very prompt set of replies from them and the matter is now in their hands. Many thanks to QrizB for pointing me in that direction, it has saved the day by the looks of it
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