Thinking about this, at the point where electricity enters the household circuit, I struggle to see a meaningful distinction between 800W arriving directly from a solar inverter and 800W arriving from a battery inverter. In either case, it is approximately 3.5A flowing into the same socket circuit. The cable, socket, consumer unit and local network do not know whether those electrons came straight from a PV panel or were stored in a battery for several hours first.

"Battery Discharge (3000W Power): The 3000W battery output operates through dedicated off-grid sockets directly powering your appliances. Because this energy does not back-feed into the wall grid, it operates as an independent EPS system without violating grid plug-in limits."

So the battery power never gets fed back into the grid and any power from the solar saved into the battery cannot be used by the house proper at this point only the sockets on it.

I can see how that might comply although it's as Sir Humphrey would probably say "a very brave intepretation" but I'm not a lawyer so whatever.

Is that a physical limit or when they sort battery out will the limitation magically change so that the battery stored power can appear on the grid tie up to 800W ?

Posted by: @editor

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Thinking about this, at the point where electricity enters the household circuit, I struggle to see a meaningful distinction between 800W arriving directly from a solar inverter and 800W arriving from a battery inverter. In either case, it is approximately 3.5A flowing into the same socket circuit. The cable, socket, consumer unit and local network do not know whether those electrons came straight from a PV panel or were stored in a battery for several hours first.

There is none.  However the regulations are the regulations.  That's why what the government has published is described as an 'interim' product spec, basically a stake in the ground to establish the main contentious principle and (largely) shut the 'established' industry up, while a full spec incorporating all variations is developed. 

It's a pragmatic reaction by government to get things moving which was made necessary because the established industry was trying all means fair and foul to block.  The government should be congratulated for doing this and the industry lambasted it's unhelpful self-serving position.  The iet in particular is a major disappointment, they have in the past been a bastion of truth over self-service but appear now to have joined the circus.  I am minded to cease my membership over this!

@jamespa @transparent 

Thank you for quoting the scope section from the DESNZ Interim Product Specification (IPS). You are absolutely right, and we appreciate the opportunity to clarify this transparently.

To address your three specific points directly:

• a) Is plug-in battery + solar covered under the Aug 27th IPS plug-in rule?

No. The Aug 27th IPS plug-and-play derogation does not cover devices with battery storage.

• b) Does the PowerFlex 3000 meet this specific IPS spec?

Because the PowerFlex 3000 includes battery storage, it falls outside the scope of the Aug 27 Plug-in Solar IPS framework and cannot be certified under that specific plug-in solar standard.

• c) Can it be plugged into a wall socket without solar to output 800W back to the grid as a battery-only device?

No, not under the Aug 27 IPS framework. The upcoming regulation does not grant a plug-and-play allowance for battery energy back-feeding through a standard BS 1363 wall plug.

How the PowerFlex 3000 can be operated legally in the UK:

1. Off-Grid / EPS Power Station Mode (Zero Grid Back-Feed):

The unit can be plugged into a standard wall socket solely to charge, while powering appliances exclusively through its built-in off-grid EPS sockets. Because zero energy flows back into the house ring main, it functions as a standard portable power station / UPS appliance.

    2. Grid-Connected Mode (Standard G98 & BS 7671 Route):
To feed energy back into the home's grid, the system must be installed via a fixed connection (e.g., dedicated fused spur / AC circuit) by a qualified electrician and registered under the standard ENA Engineering Recommendation G98 process, rather than via a standard 3-pin plug.

We apologise if our previous post conflated general 800W feed-in power capabilities with the specific scope of the Aug 27th IPS. We fully support the UK's safe deployment of renewable tech and will ensure our compliance guidelines remain entirely clear and aligned with DESNZ standards. 😀

Posted by: @etchedpixels

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"Battery Discharge (3000W Power): The 3000W battery output operates through dedicated off-grid sockets directly powering your appliances. Because this energy does not back-feed into the wall grid, it operates as an independent EPS system without violating grid plug-in limits."

 

So the battery power never gets fed back into the grid and any power from the solar saved into the battery cannot be used by the house proper at this point only the sockets on it.

I can see how that might comply although it's as Sir Humphrey would probably say "a very brave intepretation" but I'm not a lawyer so whatever.

Is that a physical limit or when they sort battery out will the limitation magically change so that the battery stored power can appear on the grid tie up to 800W ?

I think that's the issue with 'plug-in' batteries - they only want to approve appliances with inverter ratings up to 800W, which is of limited use in a battery product or appears woefully under-specified, at least in today's EPS type battery systems.

You have manufacturers like Fox who have already brought 'plug-in' systems to market such as their MiniQube 2kWh stackable systems, that have inverter ratings of 1.2kW (Octopus announced plans to release a rebranded version of these)

https://fox-ess.uk/miniqube/

It now seems very unlikely the government will approve anything higher than 800W for a plug-in battery system (for the very reasons @editor cites above), so I'm not sure where that leaves manufacturers who have already developed products, and if the inverter is limited to 800W it makes them less useful as an off grid portable EPS system, though for their target market of someone wanting to charge from balcony solar or cheap rate grid, and just cover the house background load 800W is probably still a useable inverter rating even if it doesn't fully cover the cooker, air fryer, washing machine or dishwasher, it can still significantly reduce bills and demand on the grid if widely deployed.

@etchedpixels Your understanding is spot on. When connected solely via a standard household wall plug, the battery energy (whether charged from solar or cheap grid electricity) stays isolated within the unit. It can only power appliances directly connected to its onboard AC sockets (EPS mode) and cannot be discharged back into your home’s internal grid wiring through the wall plug.

The PowerFlex 3000 is equipped with a bi-directional inverter and grid-synchronisation hardware, meaning it is physically capable of grid feed-in from the battery. To ensure strict compliance with current UK regulations, the plug-in mode operates under a firmware logic that disables battery-to-grid discharge over the wall plug.
So no magic hardware retrofit required—just the right setup (fixed G98 route today) or a potential future firmware update if the UK plug-in battery regulations evolve 🙂

@editor @editor  @jamespa @transparent 

You are correct. The definition of a "plug-in microgenerator" under the 27 August framework explicitly excludes systems designed to import electricity from the household grid for battery storage and discharge. Because our PowerFlex 3000 features bi-directional AC charging and battery storage, it does not qualify for the new 27th August plug-in solar exemption for wall sockets.

We want to unequivocally clear up any confusion from our previous comments:

1. 27 August Plug-in Solar Framework (SI 2026/848 / IPS):
The PowerFlex 3000 cannot and should not be operated as a plug-in grid-tied device via a standard BS 1363 household wall plug. The 800W limit alone does not make a battery-integrated system compliant under this specific statutory exemption.

2. Standard G98 & BS 7671 Fixed Installation Route:
For users wishing to utilize the 800W grid feed-in / battery storage / peak-shaving capabilities, the PowerFlex 3000 must be installed via a fixed AC connection (e.g., dedicated switched fused spur or AC distribution board circuit) by a qualified electrician under traditional BS 7671 guidelines and registered via standard ENA G98 notification. It cannot rely on the simple plug-in route.

3. Standalone Off-Grid / EPS Mode:
The unit can be plugged into a wall socket solely for AC grid charging, using its dedicated off-grid EPS sockets to directly power isolated appliances without any back-feed into the home wiring.

We appreciate this forum's rigorous attention to regulatory detail. It holds manufacturers to high standards, and we will update our UK product landing pages to ensure this distinction between "plug-and-play solar" and "fixed-wired battery storage (G98)" is crystal clear for UK consumers.

@old_scientist @etchedpixels 

This exact trade-off is why we designed the architecture of the PowerFlex 3000 the way we did:

1. Instead of choking the entire unit to an 800W maximum output across the board, the unit’s internal management separates grid-tie operations from its dedicated off-grid EPS sockets.

2. You are completely right that 800W is the "sweet spot" for domestic background loads.

3. Meanwhile, the onboard AC sockets retain full 3000W output capability for direct-plug appliances. Users don't have to sacrifice high-power capability (like running washing machines or power tools during an outage or off-grid) just because grid-feed regulations sit at 800W.

As you mentioned with brands like Fox ESS, the industry is transitioning through these regulatory shifts. We believe providing full 3kW hardware capability—while strictly governing grid feed-in limits via compliance settings—gives users the most future-proof setup regardless of how UK plug-in policy evolves.

On the website it clearly stated.

Dynamic electricity pricing

The Indevolt app connects to leading energy suppliers – including Nord Pool, Octopus, Tibber, and aWATTar – and analyses tariff data every 60 minutes. It charges your system when prices are low, and feeds back to the grid when prices are high, helping you make the most of every price fluctuation.

I'm guessing this is when hardwired only. There was no distinction made between hardwired and plug in.

Should I buy one, how will you know if I am going to hard wire it or plug it in?

@editor To answer your two specific questions directly:

1. Can solar power coming through the AC-coupled Backup connection charge the battery as well as supply loads?
Yes. When in "Micro-inverter coupling mode," the system manages bi-directional power flow. Excess solar power generated by the micro-inverter that isn't immediately consumed by the connected load will be directed to charge the battery.

2. Does Section 7 support conventional string inverters, or ONLY micro-inverters?
Only micro-inverters (and micro-inverter arrays). It is not designed or suitable for conventional rooftop string inverters due to differing grid-forming, frequency control, and electrical safety dynamics. 

To make integrating with external solar setups even simpler and more flexible in the future, we will also be introducing a dedicated standard DC port on future models/expansions specifically designed for direct connection with external solar micro-inverters and charge controllers.

Posted by: @old_scientist

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I think that's the issue with 'plug-in' batteries ...  inverter ratings up to 800W, which is of limited use in a battery product or appears woefully under-specified, at least in today's EPS type battery systems.

I profoundly disagree, but it is of course use case dependent. 

A plug in limited to 800W output (with, in this case, a 3kW inverter), provided it supports 2-3kW charging (input) is very useful, at least for me (see below what kit I have).  I intend buying 10kWh or thereabouts as soon as its legal.   Charge to 10kWh at cheap rate (6 hrs currently), discharge (during the heating season) at 800W when I would otherwise pay peak rate (currently 18 hrs), result = 10kWh at cheap rate that would otherwise be at peak rate. 

Outside the heating season the gain is less, perhaps 5kWh transferred from peak to off peak rate, to cover the evening load, plus a bit in addition because during the day it will be cost effective to discharge the battery (charged at off peak rate) and export from PV, rather than self consuming the PV.  I dont expect this benefit to last for long however given the current grid trends.

Payback period 3 years as opposed to 10 years with wired in = no brainer

For someone without a heat pump I suspect 5kWh or less is a better trade off just because of their reduced consumption, but the maths and trade off vs wired in will be broadly similar (why do you think the established industry has made such a strong attempt to block this?)

Wired in batteries, other than the really high end (and therefore expensive) ones, are also useless as whole house EPS devices, they are likewise essentially only useful for time shifting or for limited EPS on dedicated circuity.  

Posted by: @blizzardgreen

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Dynamic electricity pricing

The Indevolt app connects to leading energy suppliers – including Nord Pool, Octopus, Tibber, and aWATTar – and analyses tariff data every 60 minutes. It charges your system when prices are low, and feeds back to the grid when prices are high, helping you make the most of every price fluctuation.

I'm guessing this is when hardwired only. There was no distinction made between hardwired and plug in.

Should I buy one, how will you know if I am going to hard wire it or plug it in?

No reason to suppose that this is not the case if its plugged in, in fact I feel certain it is.  The limitation is that plug in batteries are not yet legal.

Posted by: @jamespa

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Dynamic electricity pricing

The Indevolt app connects to leading energy suppliers – including Nord Pool, Octopus, Tibber, and aWATTar – and analyses tariff data every 60 minutes. It charges your system when prices are low, and feeds back to the grid when prices are high, helping you make the most of every price fluctuation.

I'm guessing this is when hardwired only. There was no distinction made between hardwired and plug in.

Should I buy one, how will you know if I am going to hard wire it or plug it in?

No reason to suppose that this is not the case if its plugged in, in fact I feel certain it is.  The limitation is that plug in batteries are not yet legal.

But indevolt Tech says.

3. Standalone Off-Grid / EPS Mode:
The unit can be plugged into a wall socket solely for AC grid charging, using its dedicated off-grid EPS sockets to directly power isolated appliances without any back-feed into the home wiring.

Forgive me if I'm getting this wrong but it's all new.