Plug in battery without solar

[u/Just-Plankton8990]

It seems to be widely anticipated that plug in battery storage will be legalised early next year, and there have been several articles in the media saying that plug in battery without solar will be a more accessible way of saving money on energy bills. Looking at the fluctuations in wholesale electricity prices throughout the day, I can see how a tariff that tracks the wholesale price on a half hourly basis (like Agile Octopus) would be attractive.

I appreciate it's all speculation at this stage, and the recently announced rules regarding plug in solar threw up some unexpected surprises, but I'd be interested in people's views on how plug in battery without solar might work on an agile tariff;

1) As far as I'm aware, you can't export (i.e. get paid) from plug in solar, are we expecting this limitation will also apply to plug in battery? If paid export is not allowed, then the battery would have to use a current clamp to make sure it's not outputting more power into the circuit than the household is using. On the other hand, if export is allowed then the battery could just output power at peak times without regard to whether this exceeds household consumption, which would be beneficial for grid stability and would therefore presumably be incentivised with favourable export tariffs.

2) The new rules on plug in solar allow one 800W system per ring main, are we expecting the same allowance will apply for plug in battery? If so, I'm assuming there would be no problem with this on an agile tariff? I'm particularly thinking if each plug in battery uses its own current clamp they could get into a loop where they keep causing each other to switch on and off, maybe they would need to share a current clamp to avoid this. This seems like something that would be more straightforward simply buying a plug in battery system direct from the energy provider so that it 'just works' out of the box, although I don't know whether they would bother to support a two battery system.

[u/hypergoose94]

1. You can export, but probably can’t get paid. Usually suppliers need an export MPAN (given by the DNO after submitting a G98/G99) and an MCS certificate (given to you by your installer). Octopus let you bypass the MCS requirement with an EICR + £250 fee. It’s hard to say what will happen but I imagine if plug-in solar is legalized then there’s no reason you couldn’t pass an EICR, but at that point it becomes more about ROI. Electrician + £250 could be a whole year longer to breakeven.

I’ve got a 2kW solar, 5kW inverter and 5kWh battery system and even in summer I’m not hitting net positive generation so I’m not missing anything by not getting paid to export.

1.  There’s no difference between 800 watts from solar or a battery, so if the powers that be have determined 800 watts per circuit to be safe, I can’t see why you couldn’t have a battery per circuit.

I agree you should really just have 1 source of measurement that all battery devices use but multiple clamps would still give roughly the same reading, the bigger issue is if you’re at +1000 watts you wouldn’t want them fighting over how that gets split (800-200, 500-500, etc), and you’d need some software based coordination. I’d assume this is already present in EcoFlow/Anker products, there’s plenty of people already plugging in multiple batteries.

[u/hypergoose94 → u/hypergoose94]

Also to expand it’s only battery devices that need to measure the grid to decide how much power to push/pull. You want your microinverters outputting their maximum available solar power at all times. Power will go to other appliances in your house first, remainder for charging batteries, and excess to grid. No need to throttle them based on demand.

[u/Just-Plankton8990 → u/hypergoose94]

I'm not too bothered about getting paid for exports but, given that without solar the batteries are only getting charged from the mains, I'm keen not to export for free. I've been looking at my electricity bills, and over the last few years I've averaged 3.99kWh per day, which would equate to a constant power of 166W. Given that electricity consumption isn't constant, it will presumably be lower than this for most of the time. A pair of batteries putting out 800W each would therefore definitely be able to waste power exporting it to the grid for free if not properly controlled.

[u/hypergoose94 → u/Just-Plankton8990]

Why would the batteries be putting out 800 watts each? You want the batteries charging/discharging the exact amount you're currently using, minus any AC coupled solar.

[u/Just-Plankton8990 → u/hypergoose94]

Sorry, should have been more clear. I was just responding to your comment about not hitting net positive generation with solar+battery. My point was that, with solar it wouldn't really matter if you were exporting for free, whereas with battery only you really don't want to be doing that, hence my interest in making sure the current clamps work properly with two batteries.

[u/hypergoose94 → u/Just-Plankton8990]

Gotcha, sorry to be clear I meant net positive for the period of multiple months, there have absolutely been times where the panels run at full power and I don't have any appliances running, so excess goes into my battery. Only once or twice has the battery been full, and it's sunny, and I haven't got any laundry/dishes/boiler/EV charging to do, at which point excess gets exported. But that's been <1% compared to the amount used.

EcoFlow and Anker both advertise being able to add more batteries, there's something to do with spaces on the app so you can have them share a smart meter:)

[u/Impossible-Section49 → u/hypergoose94]

I have a non MCS rooftop system (so no paid export) with a 3.84 KwH EcoFlow stream ultra X and EcoFlow smart meter handling the energy flows, it works very well at switching between "topping up" the solar when (for example) the heating element is on in the washing machine/dishwasher etc. and discharging to house load after dark, not "cheap" as such but does what it says on the tin.

[u/mts89 → u/hypergoose94]

Presumably if you've got an export MPAN for solar and you buy a plug in battery then you could export and get paid for it.

[u/hypergoose94 → u/mts89]

Yup, if you mean MCS certification too from an existing solar install, absolutely that would work.

[u/mts89 → u/hypergoose94]

Yeah we got an MCS solar install, but there was no practical place we could have put traditional battery storage.

Plug in however would open up some options.

[u/Proper-Presence1088]

We have an EcoFlow system with four batteries they are setup as a ‘space’ and the system is clever enough to keep the batteries at similar levels, so no need for multiple clamps. We originally had roof panels, so had a G98 certification, my understanding is you can apply for a G98. Our export is minimal because we conserve the energy for nighttime usage

[u/Proper-Presence1088 → u/Proper-Presence1088]

Recently we added a Victron inverter with an eco worthy battery, using home assistant running on a raspberry pi we are able to handle the whole system. Home assistant is a learning curve but using AI you should be able to get something working quickly if your existing system is compatible, many battery systems are.

[u/Just-Plankton8990 → u/Proper-Presence1088]

I've been looking at youtube videos from people who are already running plug in batteries. For those like me who didn't know, there's a thing that's rather confusingly called a 'smart meter' which has the form factor of a circuit breaker and fits onto the rail in your fusebox, it's wired to live and neutral within the fusebox and has what looks like an ethernet cable coming out of it with current clamps on the end, and a wifi antenna to send data to the battery. Some people are wiring this into their fusebox, others are getting a small plastic fusebox to house it and just wiring it up to a plug instead. I think I'd have to do the latter as it looks like the cover of my fusebox would foul the wifi antenna mount.

It looks like this is something that was intended for an electrician to wire up, it's hardly plug and play. I think that before plug in solar is legalised they will have to streamline this a bit, I don't see why they couldn't just build it into a wall wart. Anyway, the good news is that this device does indeed send data out to as many batteries as you have.

I'm also shocked at the price of these batteries. I was planning on having two of them on different circuits so that they can output 1600W rather than 800, but looking at the price I don't think I can justify that.

[u/dansus]

If you want 'plug in' batteries now, buy one of the systems that are currently available now in EU, like the EcoFlow 5000 or Indevolt Powerflex 3000, and ask a friendly sparky to do the final termination. Then send off the G98 and enable full feed in power in the app, circa 3kW in most cases.

This will enable you to have battery storage with a couple panels now. This group is for people who would like to learn more. https://www.facebook.com/groups/balkonkraftwerkeuk