Help with first solar PV system shopping list using Victron kit

[Alexx]

Hello! I’m in the process of planning my first solar PV system and would appreciate your help. I have 6 solar PV arrays, each with different orientations and angles. I’m determined to maximise the number of panels, including on north-facing sides, by covering a garage door with vertical panels and possibly flat-mounting a couple over a dormer. It might seem excessive, but someone told me it can’t be done, so I’m set on proving them wrong the hard way!

Here’s my current list of major components—please let me know if I’m on the right track or missing anything:

• Victron MultiPlus-II 48/10000/140-100 230V (single phase) – For inverting and managing power.

• Victron SmartSolar MPPT RS 450/200-MC4 – For the 4 larger arrays.

• 2x Victron SmartSolar MPPT 150/35 – One for each of the smaller arrays.

• Victron Cerbo GX MK2 – For system monitoring and control.

• Victron Lynx Distributor – I’m unsure whether to go for the M8 version. As I understand it, this acts as a busbar to connect multiple batteries. I’m planning to start with two Gobel Power GP-SR1-PC200 16.5kWh batteries, with the option to expand to three or four later. They’re competitively priced, and I could profit from exporting at peak times or charging overnight.

• Victron Lynx Power In – Again, unsure about the M8 version. I’m still learning, but it seems to offer DC-side protection.

• Victron Energy Meter ET112 1 phase 100A max – For monitoring energy usage.

For solar panels, I’m torn between:

• JA Solar 595W N-Type Bifacial Double Glass Half-Cell-MBB

• Aiko Stellar 1N+ 645W N-Type ABC – Aiko’s marketing claims they’re “shade-proof,” which I’m sceptical about. I’m aiming for 18 panels in total.

For batteries:

• 2x Gobel Power GP-SR1-PC200 16.5kWh – These use EVE cells (same type/grade as those in EV battery modules) and offer great value.

Now, onto consumables—I’m still working out the details:

• Cables:

  • Between batteries and busbar—not sure if 50mm², 70mm², or 90mm² is best.

  • Between inverter and busbar—same uncertainty.

  • From solar PVs to MPPTs—thinking 6mm² due to long runs from the house to the MPPTs.

• MC4 connectors – For panel connections.

• Lugs – For cable terminations.

• DC isolators – One per MPPT, but should I have one per battery or just one for all? Better safe than sorry, so isolating everything might be wise.

• AC isolator – Between inverter and house. Does the inverter have a decent built-in one, or should I add an external one?

• Fuses – Should I include one per MPPT?

• Surge protection – Is this recommended? If so, one per MPPT?

• Bi-directional RCBO – For the AC side of the inverter.

Mounting rails for the sloped roof, flat roof, and vertical setup are a challenge I’ll tackle later. Right now, I’m focused on getting the Victron setup sorted, as learning and specifying the right kit is taking up most of my time.

Any advice would be greatly appreciated—cheers!

Edited April 1 by Alexx

[SteamyTea]

I cannot be bothered to go though your shopping list in detail.

But a couple or three things.

What is your expected electrical usage?

Are there any panel optimisers in there?

Why not go for microinverters?

[Alexx]

14 minutes ago, SteamyTea said:

I cannot be bothered to go though your shopping list in detail.

But a couple or three things.

What is your expected electrical usage?

Are there any panel optimisers in there?

Why not go for microinverters?

1. 20 to 30kwh a day
2. no optimisers, I will have one MPPT per array, so no need for any optimisers
3. I dislike the proprietary nature of microinverters. In my view, DC coupling batteries to solar PV makes more sense than convert DC to AC and then back to DC, then back to AC once load is generated. I even gave up on Sunsynk as it was my first option, but I want the system as open and modular as possible. I can just add a Victron EV charger later without needing any other 3rd party integrations for example.

[Dillsue]

You mention profit from export. Currently you generally need an MCS certified installer to get paid for export so you may want to get your installer involved in the design/spec to get their buy in.

[Alexx]

3 minutes ago, Dillsue said:

You mention profit from export. Currently you generally need an MCS certified installer to get paid for export so you may want to get your installer involved in the design/spec to get their buy in.

 

Octopus and some others are not requiring MCS for export. I can install it myself and still be compliant with their requirements to export as long it is all done properly. 

[Dillsue]

Octopus do accept self installed systems but there's hoops to jump through and £ to pay! Have a search on here for discussion but I think consensus seems to be it's typically not worthwhile to bag an export tariff that can be withdrawn at any time.

[Alexx]

the £250 admin fee is nothing close to the amount of money a MCS rip off company is trying to get to install the system. Solar PV installers in the UK are just taking the mickey with their pricing. 

 

I found a few topics, but they are reasonably old Has anybody managed to get a feed in tariff from Octopus without an MCS Cert? - Photovoltaics (PV) - BuildHub.org.uk

[Dillsue]

Totally agree on the MCS pricing but just giving you the heads up on export constraints. I beleive Octopus also want to see building control sign off so there's another cost to add to the Octopus fee.

[Alexx]

3 hours ago, Dillsue said:

Totally agree on the MCS pricing but just giving you the heads up on export constraints. I beleive Octopus also want to see building control sign off so there's another cost to add to the Octopus fee.

do they require that as well for normal install or just for DIY?

Edited April 1 by Alexx

[Mattg4321]

Octopus either want £250, Electrical Installation Certificate and Electrical Building Control Sign off (Part P notification) OR they want MCS 

 

 

[Alexx]

Thanks for the heads up guys. I now just need to figure out a way to get all the kit together and put the panels in place

[GavH]

You have listed a Multiplus 48/10000. Victron have recently stated that they do not see enough sales demand in the UK to warrant the expense of gaining G100 accreditation for their equipment. You will most likely need full witnessed testing of export control/limiting devices fitted to your system.

More costs to consider for the install. 

[Alexx]

it is G99 certified, I'm hoping to get 8kw allowance to export so that in theory should match my inverter and not need exporting control

[JohnMo]

On 01/04/2025 at 10:02, Alexx said:

 

Sounds a very expensive system. Lots of components - simple is normally best.

 

With lots of batteries why bother with the export side at all?

 

On 01/04/2025 at 10:02, Alexx said:

someone told me it can’t be done, so I’m set on proving them wrong the hard way

Anything can be done, sensible to do it, is another question.

On 01/04/2025 at 13:05, Alexx said:

Octopus and some others are not requiring MCS for export.

You pay to join after providing structural design etc. don't expect to make much money. It is very post code dependent. So don't hold your breath on that one.

[Dillsue]

45 minutes ago, Alexx said:

it is G99 certified, I'm hoping to get 8kw allowance to export so that in theory should match my inverter and not need exporting control

Maybe wait till you've agreed an export limit before you decide on the kit you'll use??

[Mattg4321]

6 hours ago, JohnMo said:

Sounds a very expensive system. Lots of components - simple is normally best.

 

With lots of batteries why bother with the export side at all?

 

Anything can be done, sensible to do it, is another question.

You pay to join after providing structural design etc. don't expect to make much money. It is very post code dependent. So don't hold your breath on that one.

No structural design needed for Octopus. Just need ‘Part P’ BC notification and electrical certificate, which any electrician registered with NICEIC/NAPIT etc can provide. Also DNO approval which anyone can get. Plus the £250. I did it back in September and have been paid nearly £100 already from a 4.5kWp system. Shouldn’t be far off the £250 by the end of the year, perhaps earlier, depending how the summer goes I would think. 

[pudding]

21 hours ago, JohnMo said:

With lots of batteries why bother with the export side at all?

 

You pay to join after providing structural design etc. don't expect to make much money. It is very post code dependent. So don't hold your breath on that one.

You certainly can expect to make decent money. I'm over £50 in profit this month already, that's with a GSHP& all electric house and an EV. Camelot forum might be better suited to your requests and plan, lots of similar setups and ideas there.

Edited April 16 by pudding

[JohnMo]

46 minutes ago, pudding said:

£50 in profit this month

I would never make that money as we are in an area that smart meters don't work, so best export price offered is about 4.5p, so all PV generated in March would have given me £18 in total, plus paying  for what I import.

 

So better use is to heat/cool house and heat DHW and other household uses. So in March our average per kWh was 9p based on import, PV and battery. So I am happy with that. Based on a normal 25p per kWh, saved me £135. Plus we are about 600 miles north of yourself, so PV yield is way lower, heating season longer etc.

[pudding]

Ah yes, no smart meter and no variable tariff changes things massively. Is that the case for you @Alexx or do you have a smart meter and can take advantage of variable tariffs?

[Alexx]

On 15/04/2025 at 11:15, JohnMo said:

Sounds a very expensive system. Lots of components - simple is normally best.

 

With lots of batteries why bother with the export side at all?

 

Anything can be done, sensible to do it, is another question.

You pay to join after providing structural design etc. don't expect to make much money. It is very post code dependent. So don't hold your breath on that one.

 

It is expensive, it is complex, I'm looking to make the most of a once in a lifetime kind of investment.

 

To make better return on the investment, I can lower the payback time considerably by selling excess.

 

I'm aware I'm well beyond the scope of a normal system install, I have "over engineered" things before and with time the pay back was worth it in one way or another.

 

I ended up finding an MCS installer that is flexible enough to install things in the way I want so we will be fully compliant.

 

On 15/04/2025 at 11:57, Dillsue said:

Maybe wait till you've agreed an export limit before you decide on the kit you'll use??

 

Kit is nearly all installed already, regardless what the DNO approves I will either self consume/store or limit the export rate. 

On 16/04/2025 at 09:27, pudding said:

Ah yes, no smart meter and no variable tariff changes things massively. Is that the case for you @Alexx or do you have a smart meter and can take advantage of variable tariffs?

yes I do have a smart meter, but I'm not sure which tariff I will use yet. I may end up using the flat 15p export and cheap overnight tariff. I'm also making progress with FIT that will pay probably 25% of my 8kw generation as well.

[Dillsue]

9 hours ago, Alexx said:

Kit is nearly all installed already, regardless what the DNO approves I will either self consume/store or limit the export rate. 

If you can't get consent for 8kw then you wont(shouldn't)get approval as your inverter eemingly doesn't have G100 certification to limit export below 8kw. Anything with more than 3.68kw rating and your DNO should always be your first port of call. Your MCS installer shouldn't power up, commission and certify for you without DNO consent.

 

I'd speak to your DNO ASAP and hope you can blag 8kw.

[Dillsue]

9 hours ago, Alexx said:

. I'm also making progress with FIT that will pay probably 25% of my 8kw generation as well.

The FIT scheme ended in 2019. If you mean SEG, last time I looked that generally pays a pittance- Octopuses 15p rate isn't SEG, it's a power purchase agreement that Octopus offer, can end anytime, and doesn't carry any government backing which SEG has, hence the G on the end

[Alexx]

13 hours ago, Dillsue said:

If you can't get consent for 8kw then you wont(shouldn't)get approval as your inverter eemingly doesn't have G100 certification to limit export below 8kw. Anything with more than 3.68kw rating and your DNO should always be your first port of call. Your MCS installer shouldn't power up, commission and certify for you without DNO consent.

 

I'd speak to your DNO ASAP and hope you can blag 8kw.

 

Inverter can be G100 compliant, here is a document from Victron about it. I have installed pretty much everything already. DNO has been notified, they just keep dragging their feet.

victron-g100-declaration-multi .pdf

[Alexx]

13 hours ago, Dillsue said:

The FIT scheme ended in 2019. If you mean SEG, last time I looked that generally pays a pittance- Octopuses 15p rate isn't SEG, it's a power purchase agreement that Octopus offer, can end anytime, and doesn't carry any government backing which SEG has, hence the G on the end

I have FIT from an existing installation for 2kw that was completely replaced with the Victron kit and panels. They will pay me 25% of my 8kw production, last time I had payment it was like 70p per kwh so that will definitely help with the pay back. I'm still trying to understand if I can get paid for generation and still export at 15p as well. I'm not 100% sure if I can mix and match.

[ProDave]

1 minute ago, Alexx said:

I'm still trying to understand if I can get paid for generation and still export at 15p as well. I'm not 100% sure if I can mix and match.

In theory yes.  The FIT pays for generation measured on your generation meter, plus a very much smaller rate for "deemed export" which is assumed to be half of what you generate.

 

You can give up the deemed export part of the FIT while still keeping the generation payment, and that then allows you to export on one of the SEG schemes.

 

Contact your FIT provider to discuss it with them.