What people mean by an Octopus plug-in home battery
Octopus Energy used ETS 2026 on 22 June to launch its Nook range. Two products, both due in 2027, neither on sale today:
- Nook Cube: 2 kWh, plugs into a 13A socket, aimed at renters and flats, stackable in the app up to 10 kWh on paper. 12-year warranty. No published price.
- Nook Colossus: wall-mounted, fitted by Octopus engineers, stackable up to 30 kWh, aimed at homeowners. Also 2027. Also no published price.
Search results mix those two up with plug-in solar kits (the 800W balcony panels legalised in 2026) and with adverts for socket batteries that claim to run the whole house with no electrician. Those are three different things. Only one of them is a legal whole-home battery.
There is no Octopus plug-in whole-home battery on sale this year that you can clip onto a ring main. The Cube is a small appliance for 2027. Colossus is a wall unit for 2027. If you own a house and want cheap overnight power on the consumer unit in 2026, you need a hardwired install.
Is a plug-in home battery legal in the UK?
This is the question behind most of those searches, so here it is without the marketing.
A 13A appliance that charges from a socket and powers devices from its own outlets is not the same as a house battery. Think of it as a very large power bank with a timer. The Nook Cube sits in that category. Octopus is a licensed supplier putting a brand and a 12-year warranty on it. That is new for the UK. It still does not make it a whole-home battery.
A whole-home battery sits on the house side of the meter, behind the consumer unit. It covers whatever is running, up to the inverter limit, until the stored energy is gone. In the UK that job needs an electrician, grid protection, and a legal location. The rules are G98 or G99 with your Distribution Network Operator, and BS 7671 Amendment 4 / PAS 63100 for where the box can live (garage, outbuilding, suitable outdoor wall. Not a loft, bedroom or escape route).
Plugging a battery into a UK 13A socket and pushing power back into the ring to feed the house is not a legal whole-home install. Some pages sell that idea with a CT clamp and a "no electrician" headline. We will not. Habo's 5 kWh STREAM or AC 5000 is electrician-wired, inverter in the box, G98 class. If a listing says you can run the house from a plug, treat the saving figures with the same caution.
Cube vs Colossus vs a wired 5 kWh pack
These are estimates where Octopus has not published a number. Habo prices are the waitlist offer.
| Nook Cube (announced) | Nook Colossus (announced) | Habo 5 kWh STREAM or AC 5000 | |
|---|---|---|---|
| What it is | 2 kWh 13A plug-in appliance | Wall-mounted home battery | 5 kWh all-in-one, inverter in the box |
| When you can buy it | 2027, list only | 2027, Octopus install | Install waitlist, no deposit |
| Price | Not published | Not published | From £2,499 fully installed, 0% VAT where it still applies |
| Install | Plug into a socket | Octopus engineer, wall-mounted | Electrician-wired to the consumer unit, G98 / BS 7671 |
| Whole-home backup | No | Depends on the spec. Do not assume it. | Only if the install includes backup circuits. Ask. Not a default claim. |
| Typical saving, one cycle a day | Up to about £181 to £211 a year on Go (best case) | Unknown until price and usable kWh are public | Up to about £450 to £530 a year on Octopus Go, best case (how) |
| Who it is for | Renters and flats with no wall | Homeowners willing to wait until 2027 | Homeowners who can site a small wall unit now |
The Cube maths, in brief, from the same working we use on the Nook page. A 2 kWh pack, fully cycled once a day on Octopus Go 12M Fixed (9.4p overnight against 35.3p to 39.3p in the day, checked 15 October 2026), with an assumed 90% round-trip efficiency, saves about 50p to 58p a day (2 kWh × day rate − 2 ÷ 0.9 kWh × 9.4p), or up to about £181 to £211 a year in the best case. Real savings will be lower. Five Cubes are not a 10 kWh wall battery. You need five spare sockets, each capped at 13A (about 3 kW), and you still have no whole-home backup.
Habo's 5 kWh pack on the same tariff, one cycle a day, is up to about £450 to £530 a year in the best case. Best-case payback on £2,499 is about 4.7 to 5.5 years. Real savings will be lower (see how we worked it out). Your bill, tariff and how hard you cycle the pack will move it.
Rule of thumb. If you cannot drill the wall, the Cube list is the honest Octopus answer. If you can, a socket is the wrong interface. Pay an electrician once, wire it to the consumer unit, and stop thinking about plugs.
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Should you wait until 2027?
Wait (or join the Cube list) if you rent, you are in a leasehold flat with no legal wall, or your landlord will not allow a fixed install. A 2 kWh plug-in pack is then one of the few options that does not need a consumer-unit job. Read the flats guide: home battery storage for flats.
Do not wait if you own the house and have a garage, utility, or a legal outdoor wall. Every month on a cheap overnight tariff without a battery is a month of peak-rate kilowatt-hours you could have shifted. Waiting twelve months for Colossus costs you that saving. 0% VAT on installed home batteries in England, Scotland and Wales is still due to end on 31 March 2027. After that the rate is expected to rise. Details are on VAT on home batteries.
Colossus may well be cheap at launch. Octopus has not said how cheap. "About a third cheaper than the best-known battery brands" is a Tesla-shaped comparison, not a Habo-shaped one. We walked through that on Nook vs Habo price. Until there is a published installed figure, it is not a quote you can take to the bank.
What a legal 2026 install actually is
- Survey: consumer unit, meter, a legal location under the 2026 wiring and fire rules.
- DNO: G98 notification for a small all-in-one (typically under 3.68 kW / 16A per phase). G99 if you go bigger.
- Fit: electrician hardwires the unit. Not a 13A plug.
- Setup: charge window on your cheap overnight tariff. One cycle a day is the simple pattern.
Habo is not taking deposits. Join the waitlist with email and UK postcode. Nothing to pay today, no commitment. We get in touch when we can book the installation. Pricing is on the pricing page. If you need to spread the cost, see home battery finance.
Frequently asked questions
Not yet. At ETS 2026 on 22 June, Octopus announced the Nook Cube, a 2 kWh plug-in battery aimed at renters and flats, on sale in 2027. Pricing has not been published. It is a 13A appliance. It is not a whole-home battery wired to your consumer unit, and it does not back up the house in a power cut.
A 13A appliance that charges from a socket and powers loads through its own outlets is a different product from a whole-home battery. Plugging a battery into a UK socket and feeding the house wiring from it is not a legal whole-home install. A battery that runs the house has to be electrician-wired to the consumer unit under G98 or G99 and BS 7671. That is the Habo route. Do not treat a socket pack as a substitute.
Octopus has not published a Nook Cube price. We do not estimate one. Habo's 5 kWh STREAM or AC 5000 is from £2,499 fully installed, 0% VAT where that still applies, electrician-wired, on the install waitlist. Nothing to pay today.
For a renter who cannot drill a wall, a 2 kWh Cube can shift a slice of evening load. Fully cycled once a day on Octopus Go 12M Fixed (checked 15 October 2026), with an assumed 90% round-trip efficiency, it saves up to about £181 to £211 a year in the best case. That is an estimate. It will not cover a typical house. Five Cubes are not the same as one 10 kWh wall battery: five spare sockets, five 13A limits, no whole-home backup. Homeowners with a garage, utility or suitable outdoor wall are usually better on a hardwired 5 kWh pack.
If you rent, or you live in a flat with no install path, joining the Octopus Cube list is reasonable. If you own a house and can site a wall battery legally, waiting costs you the overnight saving you could be taking now, and 0% VAT on installed home batteries is still due to end on 31 March 2027. Habo's offer is a 5 kWh STREAM or AC 5000 all-in-one from £2,499 fully installed, G98 / BS 7671, waitlist only, nothing to pay today.
Bottom line
An Octopus plug-in home battery exists as an announcement: the 2 kWh Nook Cube, 2027, renters, 13A. It is not a legal way to run a house from a socket, and it is not for sale today. If you own the walls, skip the plug. Get a G98 hardwired 5 kWh pack, charge it on a cheap overnight tariff, and stop waiting for a product that has not published a price. If you rent, the Cube list is the honest Octopus answer. Either way, do not buy a "no electrician" whole-home socket battery and call it compliant.
Join the install waitlist
Email and UK postcode so we know where you are. Optional tariff if you have it. We will let you know when we can book your installation. No spam, unsubscribe any time.
Thanks, you're on the list.