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I’m the first customer in Britain to insert a plug-and-play battery in a three-pin socket. It’s my own (tiny) power plant, connected to my house.
The energy I imported from the grid to store in it, at the rate of 12p per kilowatt-hour, is used when my electricity tariff is at its priciest peak. This week my Fox ESS MiniQube should save me about £2 — a figure that will increase as energy prices rise.
The government is legalising these devices, which are often used by households to capture excess energy generated from solar panels, for example, as part of a campaign to lower the cost of living in the face of rocketing energy bills. Fast-tracked legislation aims to get plug-in batteries “in shops within months, offering households the chance to significantly cut energy bills”.
Anyone can buy one, or several wired up together, regardless of whether they own a rural farm or rent an apartment in the city. You don’t need solar panels. The savings can come from charging up with cheap electricity during off-peak hours. And, crucially, these batteries don’t require an electrician. Renters can simply uproot their money-saving unit if they move home.
In Germany the battery revolution is in full swing, with half a million plug-and-play units being sold through outlets such as Amazon and Aldi each year. With the highest domestic energy rates in the industrialised world, perhaps it’s no wonder take-up of plug-and-play batteries there has been rapid. Many of these customers have also put solar panels on their balconies to generate extra energy without relying on the grid.
Since Britain has some of the highest electricity bills in the world, help can’t come soon enough.
The bottleneck for us has been caused by questions around the legality of plugging batteries into the mains. President Trump has inadvertently accelerated that change with his attacks on Iran and the resulting blockade in the Strait of Hormuz, pushing the red button on British energy bills.
The set-up of my Fox ESS MiniQube was simple. I unboxed the big battery, plugged it in, then wirelessly connected to the FoxCloud app. It looks like a large printer, with a digital screen showing the charge level, and can be discreetly hidden in a cupboard or placed on a shelf. As the system is modular, I can connect up to four more batteries in a stackable tower, giving me a 10kWh array. That level of battery power would significantly reduce my energy bills, but the keenly priced MiniQube is still shaving a noticeable sum off my daily bill.
The only minor faff was having to manually configure the hours in which to import and export electricity. That will change — by June 2026, when MiniQubes will be available to physically purchase in stores, energy companies should automatically optimise the savviest times to buy and sell.
So says Justin Claxton, founder of Fox ESS: “The first batch arrives in our UK warehouse in June with wifi connectivity and a smart meter built in. This will allow users to track how much money they’re saving.” Energy companies like Octopus may elect to sell plug-and-play batteries too.
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The batteries save customers money by allowing them to purchase off-peak energy cheaply, then use it when rates are high. Energy providers offer dozens of time-of-use tariffs that mirror Britain’s peaks and troughs in grid usage. For example, Octopus Cosy sells electricity for about 12p/kWh during off-peak times like 4am-7am, when factories are closed, rising to about 40p/kWh during peak times like 4pm-7pm, when Britain returns from work to put a pizza in the oven.
Potential plug-and-play savings have been wargamed by Capture Energy using several tariffs including Octopus Go, which offers off-peak rates of about 6p/kWh. Bill savings equalled about £125 a year, delivering a four-year return on investment on the MiniQube, which is expected to sell for about £500.
I can potentially profit even more by selling my MiniQube energy back to the grid at peak times, as I’ve completed all the energy export paperwork with my previously installed solar package. Capture Energy aims to launch “battery-owner tariffs that are aligned with plug-and-play batteries later this year,” says the cofounder Clemens Munter. “They have tremendous potential because they are easy to distribute and don’t require costly installation.”
Funkier plug-and-play batteries are coming too. The small British start-up Windfall Energy will ship slim, sexy 2.5kWh batteries for £1,000 from autumn. These units look like as if have been designed by Habitat, with tops that double as sidetables on which to place a mug of coffee. Windfall has “calculated savings using the example of an Octopus Intelligent Go tariff, which has off-peak rates of around 8p,” says the cofounder Rob Hallifax. Its results envisaged a £228 bill reduction a year.
Apart from buying cheap energy to utilise when prices are high, is there any other benefit to buying a plug-and-play? A battery can be used as a mobile energy unit in a garage or shed. In areas prone to blackouts, an 8kWh battery array can keep an average UK household running for 24 hours, according to Ofgem figures.
In this era of grid hacks and energy wars, owning one might prove a pre-emptive boon.
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