MSE guide: plug-in solar panels

Skintsaver

I've got a current system of 4x 400w west and 2x 400w east. I think another 4x 400w panels facing east on my flat roof would be great. I think I could just add the same 4 panels to my current string.

But would a plug in system be better? This Amazon listing seems good value.

My current inverter size is 2.6kwh.

QrizB

But would a plug in system be better?

A legal plug-in system can only be up to 800 watts AC, which means they typically only come with one or two panels.

If you want four panels, you'll need to get them permanently installed (which typically needs a Part P certified professional, at least in England). I think you have a thread ongoing about this already (edit: it's here).

This Amazon listing seems good value.

It's reasonable value. It's also not legal in the UK unless it's installed professionally.

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/82119501#Comment_82119501

Hi. I've got an Ecoflow Stream, nice kit.

But …. I think this may be a case of watch and see for multiple reasons.

First off, if you like their products, then I'd subscribe (I did) to Ecoflow, which will get you some discounts later on. Then watch all their promotions, as they go up and down constantly. That way you'll get an idea on what are the low prices, rather than the constant discounts, which all powerstation suppliers seem to offer.

Second, the PnP solar regs exclude batts. I don't think this is because they are against them, but was a way to get the regs out faster, and allow people to start getting PnP solar. So again, you'll probably be better off waiting, watching and learning. I think PnP batts with an 800W feed back to the home grid is something that millions of homes could benefit from.

Thirdly, products are changing all the time. Ecoflow has just launched their new Stream series, here's a package example with the newer, 5kWh powerstation and 2kWp of PV.

Fourthly, there are lots of similar products out there, or being launched, such as Jackery's which is launching now(ish). So maybe whilst watching and waiting (re point 2), you can double/triple check, which is the best option for you, and if you want to do this PnP or get an additional PV system / extension done by the pro's.

Hope this helps, but given we are later in the year, PnP (especially batts) hasn't settled in yet, and prices are bouncing around, I think you are in a great position to wait and learn. And of course chat away on here with allof us, looking and playing with various kit.

Skintsaver

I understand why, the pins of a plug may become live under fault conditions and a UK plug can only have 10a of constant load whereas abroad have more. Id wire this to a 20a dp switch with a bidirectional RCD. That's the easy part.

But making sure if I do get a plug in option with a battery pack is the right choice is difficult. I know my existing usage 30mins import and export ect it looks like I use just 33% of my current solar system. I currently export at 13p and import at 21.97p which is fixed for the next 2 year's.

QrizB

Id wire this to a 20a dp switch with a bidirectional RCD. That's the easy part.

A reminder that this thread is for discussion of MSE's article on GB legal plug-in solar. What you're describing is off topic. You/we can discuss it on your own thread, but please don't bring it into this one.

But making sure if I do get a plug in option with a battery pack is the right choice is difficult.

As things currently stand there are no GB legal plug-in solar options that include a battery pack. I'm not expecting to see any for at least 12 months and potentially much longer.

NedS

When I think of what the term 'plug-in' means, envisage an appliance I can go to the shops and buy, take it home and plug it in.

On a practical level, I just wonder how the average shopper living in a flat is going to get two 500W solar panels up X flights of stairs, and hoist them over the balcony to fix them in place. These things are big and awkward to handle, not to mention they weigh around 25kg. Many people will not be able to lift one, let alone get it into their flat and hoist it over a balcony. Not going to fit in a car either so you won't be picking up a plug-in solar kit in the middle isle of Lidl/Aldi.

Netexporter

I suspect Laldi, sur le continong, have a source of handy size panels, as Octopus are planning to in the future.

prowla

https://forums.moneysavingexpert.com/discussion/comment/82119112#Comment_82119112

Sorry but no: the rating of the system is what it delivers, not what a component of it is capable of producing.

The current (Amps) is pulled (by the inverter) not pushed (by the panels) and a dedicated system whose inverter is limited to 800W is incapable of pulling more.

If the panels do want to produce more they will be blocked from doing so, by what is called "clipping".

Imagine you have a bucket with a pipe going into it feeding water in and an opened tap at the bottom which lets the water out; if you fill up the bucket then the water will overflow. Now imagine that you've put a sealed lid on the bucket so it can't overflow; the tap at the bottom won't allow the water to flow out any faster, so the water will back-up along the input pipe and won't accept any more going in and effectively it is blocked by the output tap's flow rate.

That's the way electrical systems work: the sources cannot provide any more power than the pulling systems will allow.

In other words, the power of the system is defined by the inverter, not the panels: you could have 10 panels and it would still only be an 800W system.

The panels don't produce more power which disappears or something; they simply do not produce it.

P=IV is power = current x voltage; if there is no current then there is no power.

In other words, any panel rating above what the inverter will pull to achieve 800W is an irrelevance.

Regarding your house example, you can't conflate an 800W plug-in system with a full solar system + storage: there are multiple consumers of the power (ie. the storage, the grid, and each device in the house); therefore the limit of power of that system's inverter is battery charge limit + grid export limit + the consumption of each device which is consuming power.

Even the full solar system could hit the grid limit: if its battery reached 100% charge and (for demonstration puposes) every device in the house was switched off, then its production would be equal to the export rate to the grid.

The physics is the same for both setups but a plugin system is has a builtin limit of 800W, which it will never exceed.

And therefore rating a system by it's overpanelling number is a nonsense.

prowla

https://forums.moneysavingexpert.com/discussion/comment/82119501#Comment_82119501

That is not a UK-legal plug-in system, because it has storage.

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/82120147#Comment_82120147

So how do all the people in Germany manage it?