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We've got a 3.2kWp (tiny in comparison to some systems here) south facing array. Before we bought our EVs we were 7MWh yearly use - now we are a 10MWh usage. We're on Octopus Intelligent Go and fully charge the home storage batteries every night and then drain them down so they're typically around 20% before the evening's cheapslot begins. We're also on the 15p fixed export.

I really want to install another 8x ~400w panels on the north facing roof. I've got some quotes from local installers but it's difficult to justify offsetting purchasing 7p electricity at the figures that I'm getting quoted. The ROI would be many years and the wife acceptance factor on this isn't great.

The option I was thinking was to buy panels and mounting from City Plumbing and have a local roofer install them. A quote I have from a local roofer is also high at £2200. I've got a "spare" Growatt 5kW dual MPPT hybrid inverter than I can install directly in place of the existing 3.6kW, and our DNO (UK Power Networks) automatically approve up to 5kW.

Of course this wouldn't be MCS. I'm wondering if Octopus would

• notice this
• care

What do you guys think?

They won't notice if you run a complimentary DC system via a solar charge controller to your battery set up. I've heard its easy to do and that the returns are excellent

Your existing MCS gets it done.

From what I understand MCS is no longer required.
Any "competent" electrician is able to install the system and you can still get paid for export.

I would think that the DNO needs informing of the change in potential export and the relevant forms filling out. Guessing you could limit the export to zero on the new setup


Just re-reading the above. A 5kw inverter with those extra panels would clip nicely with the over panelling and provide a decent boost in low light levels.

Fueltheburn wrote: ↑Mon Sep 09, 2024 7:40 pm From what I understand MCS is no longer required.
Any "competent" electrician is able to install the system and you can still get paid for export.

I would think that the DNO needs informing of the change in potential export and the relevant forms filling out. Guessing you could limit the export to zero on the new setup


Just re-reading the above. A 5kw inverter with those extra panels would clip nicely with the over panelling and provide a decent boost in low light levels.

Sorry, I disagree with the no mcs req. Very much a stipulation when I went for Export contract with Octopus recently (June 24). Even their self certification path (which is inspected anyway) costs £200 and then onto a waiting list. I'd be very happy to be shown otherwise though?

From what I read, it was Octopus who stated they no longer required MCS.

Going through section 5.5 and 5.8 it is in reference to the "equipment" must be certified to MCS standards.

You can in fact get it installed by someone competent BUT Octopus accept no liability for any shortfall with installation standards noted in 5.8.

https://octopus.energy/policies/export- ... onditions/

Fueltheburn wrote: ↑Mon Sep 09, 2024 9:02 pm From what I read, it was Octopus who stated they no longer required MCS.

Going through section 5.5 and 5.8 it is in reference to the "equipment" must be certified to MCS standards.

You can in fact get it installed by someone competent BUT Octopus accept no liability for any shortfall with installation standards noted in 5.8.

https://octopus.energy/policies/export- ... onditions/

I knew about this a while back but it's not as simple as one would think. I had hoped there had been a development.

I'd be interested to read of anyone who has successfully went through the process to export contract without MCS? More knowledge for all? When I asked about it the other month for No1 son's balcony system I met the £200 cost, engineer visit and the waiting list without going into any equipment detail at all. Seemed like a stock answer.

Flexi orb, that was the £200 hit, I'd forgot the name. Sec 5.5.

"(ii) the Flexible Energy Oversight Registration Body (Flexi-Orb); or

(iii) an equivalent certification scheme recognised by Octopus Energy (an equivalent scheme is a scheme accredited in accordance with EN 45011 or EN ISO/IEC 17065:2012)."

Although I can see it being worthwhile to pay for the flexi orb if the PV diy install is of a decent size. Not though for a 800W install as present at my sons place.

Apologies, £250 not £200 for a engineer to come and inspect diy system. It does make sense if you've no MCS or flexi orb cert on any part of systems and its a decent size. Looking about on the net and there is a partial refund of fee if system does not pass muster.

"In order to set up your export, we require either an MCS or Flexi-Orb certificate. If you do not have either of these certificates, we can still proceed with the non-certified route, but please be aware that there will be a £250 admin fee associated with this option and it will be managed by our engineering service: OES. If you're happy to go via this route, or if you do have a Flexi-Orb certificate, please let me know so I can send you the form to apply!"

Also the query went to Octopus in February 24!

I like that there is a non certified route to pursue.

Who knows what checks octopus do?

They could;
-Monitor export and flag anything over stated capacity registered with MCS/DNO
-Monitor usage and export intelligently and surmise that the profile smells fishy, compared with what's declared.
-See a valid MCS certificate and make no more checks.

To play it safe with an under the radar installation, you'd have to not declare to DNO and export limit to not exceed MCS export limit. That seems a silly option as your DNO will let you install the amount you want and what would the fine be if caught without DNO approval?

So, you could DNO approve and export limit and hope octopus don't check DNO records, which they possibly won't. Especially if you've already set up a contract with them.

But that limits you to your old inverter capacity for export.

Feels like the riskiest option wrt octopus is to sign off with DNO and up export capacity without getting a new MCS cert to match.

Why not explore a compromise solution - try to find an MCS installer who will install the AC side and, with appropriate documentation from yourself, provide an MCS certificate. This is within the rules and you may be able to find an MCS installer who will do it. Installing an inverter and prepping a certificate having someone else do the roof work is win, win for an installer who can't find enough staff to do roof work.

Have to ask though, is a North facing array worth the expense? What's a back of the envelope payback calculation look like?

Then you have the other complication of an install/application like mine to chuck in the mix.

Im not on any export contract or anything with my Sunsynk system, but im looking that way as it seems im missing a fair chunk of cash as a low user with high export potential.
Anyway, my 5.45kw system IS MCS certificated, so happy days = easy peasy application.
However im having it extended shortly to approx 7.1kw.
So am assuming i could just dish out the 5.45kw MCS certificate i already have to Octopus regardless and run on the 7.1kw - my invertor will be remaining the same for either.

Just gets too confusing.

resybaby wrote: ↑Tue Sep 10, 2024 10:24 am Then you have the other complication of an install/application like mine to chuck in the mix.

Im not on any export contract or anything with my Sunsynk system, but im looking that way as it seems im missing a fair chunk of cash as a low user with high export potential.
Anyway, my 5.45kw system IS MCS certificated, so happy days = easy peasy application.
However im having it extended shortly to approx 7.1kw.
So am assuming i could just dish out the 5.45kw MCS certificate i already have to Octopus regardless and run on the 7.1kw - my invertor will be remaining the same for either.

Just gets too confusing.

Yep, to keep it simple (for me), they DNO only care about your AC connected gear. If they haven't been informed by installer about your system connection (as happened with mine) the dno have a self declaration form you can fill in. Octopus only want your mcs No if you have one. I photocopied the mcs cert and sent it to them.

Going back to the OP's original question, If i was installing from new today i'd still go for a MCS cert. Once you've got that you can diy to you hearts content & skill. If I had an already installed system i'd be pursuing that original install MCS cert as it has a high return value no hassle aura about it. Im sure if the original installer is no more a copy of cert can be sourced via MCS body my email?