Can I add a battery to a plug-in solar kit?
The short answer
No. Batteries are outside the rules, and no compliant kit has one.
A battery would solve the biggest weakness of plug-in solar, which is why people keep asking. The law that legalised plug-in solar deliberately excluded it, and the government has not said when that will change.
Every honest assessment of plug-in solar runs into the same wall: the kit makes its electricity at midday and most people need it at seven in the evening. A battery would bridge that. It would take a household from using 40 per cent of what the kit makes to using nearly all of it, and roughly double the saving.
It is not allowed yet. Here is exactly why, and what that means for what you can buy.
What the law says
The regulation that created the plug-in exception defines the device it permits, and that definition specifically excludes anything “designed to import electrical energy for the purpose of storing energy for later supply”. A device that charges from the mains is not a plug-in solar device in the eyes of the law.
The product specification says the same from the other direction. Its scope excludes “plug-in battery systems” and “plug-in solar PV devices integrated with battery systems”. And it requires the instructions supplied with your kit to warn that the device “is not intended to be connected to, operated with, or used in conjunction with a battery energy storage system”.
So it is not an oversight, and it is not a grey area. It is three separate documents saying the same thing.
The government’s position
In its July 2026 response to the consultation, the government said battery-integrated products “remain outside the scope” of both the specification and the regulations, and that it “will continue to develop evidence relating to battery-integrated products”. It also said the framework “is not intended to permit battery storage systems, portable generators, or wider categories of plug-connected generation equipment”.
Read that as: not now, possibly later, no date. Octopus Energy has said it hopes plug-in batteries that can export will be available in early 2027. That is one company’s expectation, not a policy announcement, and we would not plan around it.
Kits that are sold near batteries
This is where care is needed, because some makers sell a compliant plug-in inverter and a battery from the same range.
None of the compliant entries on the ENA register describes a battery. The registered products are the solar kits. But at least one maker lists an expansion battery as compatible with the same inverter family elsewhere in its range, and that combination has not been type tested for the UK rules.
Adding a battery to a compliant kit takes your setup outside the rules. The device you registered is no longer the device you are running. Whatever the maker’s European page says, and however easy the connector makes it look, that is the position in England, Scotland and Wales today.
What you can do instead
- Shift your use to the middle of the day. A timer on the washing machine is a free battery. Dishwasher, laundry, dryer, breadmaker, hot water immersion if you have one: all of it at noon.
- Let your background load soak it up. Fridge, freezer, router, standby: typically 150W to 300W around the clock, which a kit covers on any half-decent day.
- If you have an electric car, charge it in the day when you can. A kit will not fill it, but 800W into a car for six hours is still six hours you are not buying.
- Consider a conventional installed system instead if storage is what you are really after. A proper installation with a battery is a different product at a different price, with an installer, a formal connection and access to export payments.
Questions people ask
What about a portable power station charged from the panels?
Charging a portable power station directly from a solar panel, with nothing connected to your house wiring, is a different thing entirely and is not what these rules cover. What you cannot do is put a battery into the path between a registered plug-in kit and your mains socket.
Is it dangerous, or just not allowed?
We are not going to speculate. What we can say is that the rules exist so that anything pushing power into a domestic socket has been tested against a published standard, and a battery-plus-kit combination has not been tested against it. That is reason enough.
Will the rules change?
Possibly. The government said it is continuing to develop evidence. We will update this page when there is something official to report, and we will say the date we checked. If you want to know when that happens, it will be in our news.
Sources: SI 2026 No. 848; the Plug-in Solar Device Interim Product Specification version 2 (16 July 2026), scope and section 8.3; the government response to the plug-in solar consultation, July 2026; the ENA Connect Direct Type Test Register, plug-in solar category, read 26 September 2026; Octopus Energy plug-in solar guidance, read 26 September 2026. Position as at 26 September 2026.