Plug in solar

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/82079682#Comment_82079682

I believe the worry with a non bidirectional RCD feeding a generator is that it may burn out if it ever does trip.

There will be some electronics to detect a fault, and an electromagnet to pull the switch off if it detects a fault.

Normally, once the breaker is off, the electronics and electromagnet will lose power. But if it's feeding a generator, that could keep generating power. So the electronics would see the power still on and keep trying to turn the power off until the thing burns out.

That shouldn't be a problem with a properly made balcony solar system, as they are designed to shut down within a fraction of a second of losing their mains connection.

There's another unrelated issue that many homes are still fitted with type AC breakers. These are considered obsolete now as they might fail to trip if they are powering faulty electronic gadgets. The sort of things our homes are stuffed full of these days. A properly built balcony solar inverter shouldn't make things any worse.

Qyburn

https://forums.moneysavingexpert.com/discussion/comment/82079682#Comment_82079682

I must confess that I have lost the plot with all the discussions about RCD's.

There are two potential issues, both of which should be addressed within the product.

"Bidirectional" the concern is that when an RCD goes off, either switched or tripped, it might be damaged if the electronics are still energised from the load side. Bidirectional RCDs have an additional contact that isolates the electronics.

"Type A A/C etc". The concern is DC leakage. With some types of RCD this biases the sensing circuit, so it won't correctly detect an actual fault. The Interim Product Specification addresses this by requiring the devices to be tested to confirm less than 5mA.

Scot_39

1. Meter types and restricted circuits. Single vs twin element dual meter E7 / E10 / RTS replacements.

Given my meter is a single element meter - does it matter which port / circuit is using the electricity - or is it a simple net sum use across all active circuits

(With all contactors closed / RCDs not tripped - am I naive in thinking it makes no difference which meter port / house circuit the power is drawn from - as all demands and the solar supply itself would all be downstream of the measuring point on a single element meter)

And taking the ideal with just one system (plug in) generating its 800W

With a load around 100W (tv+base load 20W+led light say) - I'd be exporting 700W for no benefit - but paying nothing

if I put 3 kW kettle on (or WM heater or oven for longer) Id only increase my billed import use by 3kW-previously exported 0.7kW = paying for 2.3kW ?

and

that if my 3kW HW immersion kicked in (as does at 2pm in BST) - when hopefully solar at or near its daily max - on restricted - I'd still only see 2.3kW net import consumption - despite it being on the meter restricted feed.

(II know it sounds perverse - but in terms of payback calcs - saving for even upto the typical 20m on all 800W - 260Wh - is several hours of my even lower home empty - dips as low as 20W energy demand - even with FF averages below 50W when away in summer - maybe 20m equiv to 5 hrs on many days)

But then for those with a twin element RTS replacement say - with their heating on the secondary - it would only be net sum - on the 24/7 live primary feed - no impact on the secondary measurement at all.

So still exporting 700W for nothing on primary - and secondary reading the full 3kW etc ?

2. SEG for self install

Re the 700W for nothing question

This site - just one that came up on google - holds out a glimmer of hope

https://www.balconysolarguide.co.uk/guides/balcony-solar-seg-tariffs

"

As of March 2026, DIY plug-in balcony solar installations cannot be
registered for the Smart Export Guarantee due to the MCS certification
requirement. This is expected to change as part of the government's
legalisation framework, but no simplified pathway is yet in place.

"

Has anyone seen anything on official govt channels indicating thats going to happen ?

Qyburn

https://forums.moneysavingexpert.com/discussion/comment/82080390#Comment_82080390

Given my meter is a single element meter - does it matter which port / circuit is using the electricity - or is it a simple net sum use across all active circuits

Simple net sum. 800W generation, 100W load on unrestricted plus 3,000W on restricted, you'll be importing 2,300W

With two separate meter export from one won't credit the other. Same scenario, one meter would be exporting 700W and the other importing 3,000W.

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/82080390#Comment_82080390

With E7 or similar, the solar needs to be connected to a circuit that's on all the time. That should be most sockets. It's not a lot of use to have solar that's only connected to the mains at night!

As for using the power, you're right. If you are using less than the solar is generating, the rest disappears into the grid. Without an MCS installation certificate (which you won't get on a self install) you don't get paid for that. If you use more than the solar is generating, then the solar reduces the amount you draw from the grid, and you save money.

Scot_39

https://forums.moneysavingexpert.com/discussion/comment/82080517#Comment_82080517

thanks - of course the twin element case is 2 essentially 2 independent meters in one physical meter - sone even report retain the 2 mpans on bills iirc - some may not realise the significance - which is why I thought Id check / ask the question.

tlcgrantham

Who actually benefits from all the “free electricity” that goes back to the grid? Couldn’t they offer subsidised plug in systems knowing they’ll get their money back?

TroubledTarts

https://forums.moneysavingexpert.com/discussion/comment/82080762#Comment_82080762

I am sure a company like Octopus are looking into this.

I have specifically asked if they will open up this scheme to plug in solar

https://octopus.energy/help-and-faqs/articles/export-without-mcs/

Scot_39

https://forums.moneysavingexpert.com/discussion/comment/82080762#Comment_82080762

who is the they - your few 100Wh of export might be sold to your neighbours etc - but not by your own supplier.

And you presume that electricity is worth sonething when uk regularly sees negstive plunge pricing on sunny breezy summer days.

Untied solar rates are already as low as 1-3p per kWh - its not worth the risk - even to a big player lije Octopus who might get say 20% back in others import on average - and of course as a commercial company - they alonehave have reportedly c5.7 GWp of their own solar output to sell -jncreasinyly at plunge prices - due to uks imbalanced grid.

QrizB

Who actually benefits from all the “free electricity” that goes back to the grid?

We all do; it shows up as reduced transmission losses, which means slightly lower allowances for losses when the cost of power and standing charges are calculated.

But it's a drop in the ocean.