Yes ELVs <50Vdc.  IMHO its sheer madness to be involved with MV dc Panel strings - way too dangerous  IMHO in a domestic environment, and we dont have the skilled tradesmen to recognise this type of micro grid nor is there a recognised route to upgrade to this unfamiliar but hazardous system.  Way too many unschooled wannabees playing with fireworks.  It is utter negligence by our Political leaders to allow this to continue.  They only woke up to the hazards of amateur plumbers who didnt understand flammable atmospheres till a few houses were blown up flattened.  Then British gas had to step in a institute proper training courses with local tech colleges.  Where do our Electricians get proper upgrades?  A one man jobber cant afford an apprentice (with all the paperwork and oversight involved). He will only have a family member or friend involved.

I would hope that most domestic installs would be done by an MCS approved, qualified electrician.  If nothing else, you'd struggle to get export payments on a DIY system.

I've checked the logs from my system today.  It has two series strings, and each produced up to about 4A at 350V.  Nothing that an ordinary electrician couldn't handle.  It's well within the limit for LV.

I would hope that most domestic installs would be done by an MCS approved, qualified electrician.  If nothing else, you'd struggle to get export payments on a DIY system.

I've checked the logs from my system today.  It has two series strings, and each produced up to about 4A at 350V.  Nothing that an ordinary electrician couldn't handle.  It's well within the limit for LV.

Octopus Energy recently updated their T&C’s to remove the requirement for an MCS Certificate, The SEG terms already had alternatives to MCS.

I am aware of two installs without an MCS cert who do get Export payments.

However, SEG and export are not worth the aggravation for the payback these days.

In a good amount of cases you can get a far better installation by going to a good quality electrician rather than an MCS installer - the shocking statistics on poor installations would seem to support this. 

Pandora's box has been opened here

Microgeneration Certification Scheme (MCS)

https://www.gov.uk/government/publications/register-energy-devices-in-homes-or-small-businesses-guidance-for-device-owners-and-installation-contractors/register-energy-devices-in-homes-or-small-businesses-guidance-for-device-owners-and-installation-contractors

Just when you thought that the summary dumping of Part P responsibilities on to the LABC (who had no historical involvement in electrical installations) was a complete dog's breakfast, and IMHO remains so to this day and from experiences of Landlords, widely open to brown envelopes.

Remember gentlepersons that the domestic electrician's primary skill involves "house bashing - that's a trade term and needs years of experience" - this is not to be deprecated in anyway. The industrial electrician is an elite class holding authentic credentials in order to be allowed on site or employed by a Company.  These persons wouldnt trade their coveted positions for the Solar Wild West country.

The average domestic electrician is a sole trader operating from home and he has to weigh the costs of trading legitimately against competing with rogue chancers who abound.  You can be a hairdresser today, slap some stick on vinyl flashy advert on the side of your van and carry on as "Instant Electrics".  Here today, gone tomorrow Strawman.

Given that over half the cost of a Roof Panel installation comes from labour and scaffolding (mandatory ???) you can see that installation persons dont need any electrical certification (maybe half day course on how to use a ladder) and can plug in MC4s (even crimp them up).  We have the dubious practice of a young persons finishing tails under supervision of a "Competent Person"  You get the picture?

Nowhere in any of this labyrinth of obfuscation is there any requirement for anyone to be properly trained in dc power systems. As a certified and authentic EE (not Power btw) I have spent a year looking at the problems of domestic DIY Solar systems on most of the relevant Forums covering USA/CA OZ EU and the Leisure craft/RV.

If you want a good example of the kind of hazards you can face then the widely acclaimed site https://www.youtube.com/@OffGridGarageAustralia  will surely open your eyes.  Ignore all the bells and whistles of batteries and BMS just look behind at the electrical installation behind it all  and think about kids playing with fireworks with a can of petrol nearby.  The guy is a former IT technician and it shows a superficial grasp of dc power systems  (think of MCBs for solar panel disconnect under full sunshine  an OZ scandal since corrected when resulting in numerous alarming arc flash fires)

(FYI the ABYC has a long history and wealth of experience  certifying electrical systems on boats, they have their own "Codes" and authorised inspectors to UL standards - if your craft is not signed off you dont get insurance and that limits where you can moor your boat - its quite draconian and there are numerous examples of fire aboard caused by electrical faults)

There is no credible UK Solar forum to exchange User experience.  We cant even recognise the problem of highly publicised  Escooter fires from faulty products we blithely allow to be imported from Cheap Charlie  see YT https://www.youtube.com/results?search_query=escooter+fires.  The CE mark is a treacherous joke (meaning China Export)

I've been looking at this recently. I'm building a house in Scotland, part of the Planning requirement is to have PV panels. (I'd have them anyway). I've had one quote, and , asking around, its a typical, maybe low price, 4kW PV, 10kW battery, supplied and fitted for £8850.

Now, money is getting tight, so looking around, the same materials, can be bought for £5500. That's some mark up to fit those for £8850, especially as the scaffold will already be up, and the Roofer is fitting the trays to mount them (in roof system). I can fit the panels/inverter etc myself, but need the MCS sign off. Except I no longer need that, as Octopus will allow PV export with just an electricians sign off, no need for the MCS requirement, hence now, I'll be DIYing.

MCS is also changing this year, there are far too many complaints that their eligibility requirements are too tight, rumour has it that entrance to their scheme is going to be loosened a lot. It's a same scenario in the Heat Pump world, good sole traders are not bothering trying for MCS as the costs and paperwork requirements are far too stringent, so good Designers and Installers are not fitting heat pumps, as they are not allowed to apply for the £7500 grant, yet Octopus/BG et al are fitting them with an awful design (50 deg C flow temperature) that will be fitted cheaply, but will cost the customer a lot more in the long run with their poor performance and increased electric usage.

Well Alan that sums up our typical bureaucratic incompetence we've come to expect. Armchair diktats from faceless mandarins.

IMHO if you can at all then instal ground level panels.  There are numerous horror stories of roof panels - gggle and yt for info.  Tip to consider as its new build, install a cat walk tray on your roof ridge and make it accessible from a gable end by ladder. Its and unobtrusive convenience for maintenance which you will need.

Wire each panel with its own cable thru ridge into loft space and route to a marshalling cabinet and maybe use panel optomisers. You avoid the dubious MC4 connectors (use barrel but splice ferrules and heat shrink apply si grease around metal then a 50mm length of 4:1 adhesive sleeves - these make a water resistant cover

Beware of fake Solar cable (4mm2 solar as 6mm2 solar)

Are you sure your location and insolation (sunshine hours) can justify the full expense of a solar system - capex vs payback time (10yrs +).  Dont believe Solar cowboy calcs. Octopus are just a shed load of accountants check very carefully TnC.  How much energy do you expect to export? Is it really worth it, store your excess as hot water or underfloor heating.  This Solar thing in Scotland has to be one of those political panjandrums  BEWARE

Martyn said:

However, SEG and export are not worth the aggravation for the payback these days

I tried doing some rough example calculations.  Say you average 2kW export for 6 hours a day.  Sign up with a supplier who offers £0.15/kWh.  That's about £657 per year.

The panels could pay for themselves in 10 years.

(use barrel but splice ferrules and heat shrink apply si grease around metal then a 50mm length of 4:1 adhesive sleeves - these make a water resistant cover

Are you sure such an arrangement would meet BS 7671 requirements for joints (526.5)?

   - Andy.

Simon Barker said:

The panels could pay for themselves in 10 years.

Have you amortised the total cost of installation inc wiring switchgear inverter (fails in 5 years maybe) panels need replacing etc?  Batteries?

AJJewsbury said:

Are you sure such an arrangement would meet BS 7671 requirements for joints (526.5)?

I cant justify purchase of IEE regs plus add plus the user manual, not a practising designer anymore

can you quote the relevant excerpt 526.5 that outlaws crimped joints?

OBTW what I meant was "paraphrase" the relevant passage (mustnt violate copyright), but explaining/discussing an extract is ok

can you quote the relevant excerpt 526.5 that outlaws crimped joints?

It wasn't the crimp I was alluding to, but the method of enclosure...

526.5 Every termination and joint of a live conductor or a PEN conductor shall be made within one of the following or a combination thereof:

(i) A suitable accessory complying with the appropriate product standard

(ii)An equipment enclosure complying with the appropriate product standard

(iii) An enclosure partially formed or completed with building material which is non-combustible when tested to BS 476-4.

which a bit of heatshrink doesn't obviously meet, if used on its own to extend tails to reach your marshalling boxes.

   - Andy.