Home battery without solar in the UK: when charging at night pays
Charging from the grid on a cheap rate and using it at peak: the price spread, round trip losses and cost per stored kWh in a worked example, plus the rules in Great Britain.
Last checked on 8 November 2026
How a battery without panels works
A battery without solar does one job: it buys electricity when it is cheap and gives it back when it is expensive. That only works on a tariff with different prices at different times. Smart Energy GB describes time of use tariffs as offering cheaper rates off peak, for example at night or when a lot of wind or solar power is generated, and states that all new flexible time of use tariffs need a smart meter. On a flat rate tariff, a battery without panels saves nothing and loses a little on every cycle.
What decides whether it pays
Four numbers decide it. The price spread between the cheap and the peak rate. The round trip efficiency: you buy more kWh than you get back, so the cheap rate effectively rises. The cost per stored kWh: purchase price divided by all the kWh the battery will deliver over its life. And how many cycles you really use: one full cycle a day is the most a single cheap window allows. A rule of thumb follows from this: the battery pays only if the peak rate is higher than the cheap rate divided by the efficiency, plus the cost per stored kWh.
A worked example
All figures here are assumptions chosen for the arithmetic, not prices from a real tariff or product: a cheap rate of 8 p per kWh, a peak rate of 28 p, a battery with 5 kWh usable, 90 percent round trip efficiency, £3,000 installed, one full cycle a day for ten years. Each night you buy about 5.6 kWh for 44 p and avoid 5 kWh at peak, worth 140 p. That is about 96 p a day, or about £349 a year, so the battery is paid back after about 8.6 years if nothing else changes.
Now the same case per kWh. Ten years of daily cycles give 18,250 kWh, so the battery costs about 16.4 p per stored kWh. The margin per kWh is 28 p minus 8.9 p (8 p divided by 0.9), about 19.1 p. Only about 2.7 p per kWh is left, roughly £490 over ten years. With a spread of 8 p and 20 p instead, the margin falls to about 11.1 p, below the 16.4 p the battery costs, and it never pays. Capacity loss with age, a shorter life or a tariff change shift the result further, so check these numbers with your own tariff before you buy.
Great Britain: an installation, not a plug in device
The new plug in route in Great Britain covers solar devices only. The government response of July 2026 states that battery integrated products remain outside the scope of the product specification and the regulatory changes, and that the framework is not intended to permit battery storage systems. A home battery is therefore wired into the house's electrical installation by an installer, not plugged into a socket.
There is one advantage. HMRC's VAT notice 708/6 says that since 1 February 2024 the temporary zero rate covers the installation of a standalone battery storing electricity from the grid in a home. The zero rate on energy saving materials runs until 31 March 2027, after which the notice says it reverts to 5 percent. It applies to supply with installation; a battery supplied without installation is charged at the standard rate.
A portable power station as a small alternative
A portable power station is an appliance you charge from a socket, and it powers only what is plugged into it; it does not feed the house wiring. The arithmetic above applies in the same way, at a smaller scale. EcoFlow lists the Delta 3 with 1,024 Wh, 1,800 W AC output and 4,000 cycles to at least 80 percent capacity. One charge a night shifts about 1 kWh: enough for a fridge, a router or a laptop through the peak, and a real backup in a power cut.
Before you buy
Write down your own cheap and peak rates and how many kWh you use in the peak window. Divide the battery's price by the kWh it can deliver over the years you expect to keep it, not over its rated cycles. If the margin per kWh is small, a power station for backup and shifting a few appliances to the cheap hours may be the better first step.