Home battery storage without solar: charging from the grid
A battery doesn't need panels. On a tariff whose price changes through the day, it can fill during the cheaper hours and run the house later. Whether that helps depends on your tariff and how your use is spread over the day.
In short
Without panels, a home battery charges from the grid during a tariff's cheaper hours and supplies the house at other times. It can move at most its usable size, or the use you have outside the cheap hours, whichever is smaller, and it loses a little energy each cycle. It needs a time-of-use type tariff, which usually means a smart meter.
How much a battery could move
The helper works in kWh only. Give it your yearly use, the share already falling in your tariff's cheap hours, the battery's usable size and its round-trip efficiency from the specification sheet. It shows the energy a battery could move into the cheap hours each day, and how much it would draw from the grid to do so.
There are no starting values here except the Economy 7 night share in the label. Your tariff's hours, your habits and the battery's efficiency are all specific to you, and a made-up default would give a made-up answer.
Shift = the smaller of two numbers
The battery can move whichever is smaller: its usable size, or the use you have outside the cheap hours. Charging it draws a little more than it gives back, because of the round-trip efficiency on the spec sheet.
Fill in all four boxes with your own figures to see it in kWh.
Tariffs that make grid charging possible
Charging a battery from the grid only makes sense if electricity is cheaper at some times than others. Citizens Advice describes the main types:
| Tariff type | How the price changes | For a grid-charged battery |
|---|---|---|
| Single rate | One unit price all day | No cheaper window to charge in |
| Economy 7 or Economy 10 | A cheaper rate for set night (or night and afternoon) hours | Fixed windows; the battery charges in them |
| Fixed time-of-use | Set cheaper and dearer periods each day | Charge in the cheap period, use at the peak |
| Dynamic | Prices move with the wholesale market, often half-hour by half-hour | The cheap hours move; the battery's schedule has to follow them |
Most time-of-use and dynamic tariffs need a smart meter that records half-hourly readings. Tariff terms change, and some tariffs are designed around particular equipment, so read the terms before assuming a battery can charge at a tariff's cheapest rate. This guide works in energy only and quotes no prices; whether a shift of so many kWh is worth having depends on the prices on your own tariff.
The two limits on a grid-charged battery
Your use outside the cheap hours
A battery can only supply energy the house would otherwise buy at a dearer time. If 40% of your use already falls in the cheap window, only the other 60% is available to shift. Ofgem's figures assume Economy 7 homes use 42% of their electricity at night and 58% by day, which gives a sense of scale for those meters.
Applied to Ofgem's three multi-rate values, that 58% daytime share comes to about 3.0 kWh a day for a low-use home, 5.4 kWh for a medium one and 9.7 kWh for a high one (our arithmetic, spreading each year evenly over 365 days). On an average day, that is the most a battery filled in the night window could usefully hand back before losses. Usable capacity well beyond your own figure would, most days, still be holding charge when the cheap hours come round again.
Its usable size
A battery that is emptied every evening and refilled every night shifts, at most, its usable capacity each day. A battery bigger than your daytime and evening use will not be emptied, so part of it goes unused.
The length of the cheap window, in hours
The cheap hours are a time budget as well as a price. Citizens Advice says Economy 7 usually gives seven off-peak hours in one overnight block, such as 11pm to 6am, while Economy 10 gives ten hours that may be split up, for example into an afternoon block, an evening block and five hours after midnight. Charging power in kW multiplied by hours sets how much a battery can take in. Drawing 10 kWh from the grid in seven hours needs an average of about 1.4 kW; in a five-hour block it needs 2 kW, and in a three-hour block about 3.3 kW (our arithmetic). Compare the maximum charging power on the specification sheet with the shortest block you plan to use. A split window also lets a battery top up in the afternoon as well as overnight, so the energy it moves in a day is no longer limited to one fill, although each extra cycle carries its own losses.
When the cheap hours move
On a dynamic tariff the cheaper periods are not fixed. Citizens Advice notes that you may get a day's notice of them, or less than an hour, and that tracker tariffs change once a day, usually with the next day's rate given the day before. A timer set once cannot follow that; the battery's controls have to pick up the new hours as they are published. Ask how the system you are offered learns your tariff's cheap periods, and what it does if that information stops arriving. If you have no smart meter, Citizens Advice says Economy 7 and Economy 10 can usually still be had with a two-rate meter, so those remain open to a battery in a home without one.
Losses every cycle
To give back one kWh, a battery has to take in a little more, because of the round-trip efficiency. A battery charged from the grid every night pays that loss on every cycle, whereas one fed by spare solar pays it on energy that would otherwise have been exported. The round-trip efficiency guide explains the figure on the specification sheet.
What still applies without panels
- Network notification. A battery charging from and possibly exporting to the grid is notified to the network operator like any other: G98 within 28 days for small systems, G99 before installation for storage over 3.68 kW. See G98 and G99.
- Where it can go. PAS 63100's location rules are the same with or without solar. See where to put a home battery.
- Power cuts. A grid-charged battery without a backup function switches off in a cut like any other. See backup in a power cut.
- Exporting. GOV.UK says a storage device that can import and export could be used to benefit from the Smart Export Guarantee, but the rules expect a certified installation and suppliers' terms differ; see exporting from a battery.
Later adding panels to a grid-charged battery is possible in principle, but the connection type matters: ask at the start whether the system you are offered could take panels later and what that would involve. Storage for existing panels explains AC and DC coupling, and the tariffs guide goes further into tariff types.
What this page is based on
- Citizens Advice: choosing an energy tariff (fixed, variable, time-of-use and Economy 7) (read 3 Nov 2026)
- Ofgem decision on typical domestic consumption values (May 2026, in use from 1 July 2026), PDF (read 3 Nov 2026)
- MCS guidance for installers on telling the network operator (G98 and G99) (read 3 Nov 2026)
- PAS 63100:2024, fire protection for battery energy storage in dwellings (BSI, sponsored by DESNZ), PDF (read 3 Nov 2026)
- Electricity Safety, Quality and Continuity Regulations 2002, regulation 22 (sources running in parallel with the network) (read 3 Nov 2026)
- GOV.UK guide to the Smart Export Guarantee (read 3 Nov 2026)
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