Time-of-use tariffs and home batteries: the types explained
A battery with no panels is only as useful as the gap between your tariff's cheap and dear hours, and a battery with panels can use that gap in winter. This guide explains the tariff types in energy terms, without quoting any prices.
In short
Single-rate tariffs charge the same all day, so a grid-charged battery has nothing to work with. Economy 7 and 10 have fixed cheaper hours; fixed time-of-use tariffs set cheaper and dearer periods each day; dynamic tariffs move with wholesale prices. Most time-of-use tariffs need a smart meter, and terms vary, so check them before relying on battery charging.
The four types
Citizens Advice describes the tariff types available to households. Here is what each means for a battery, in energy terms.
| Type | Cheaper hours | Smart meter | Battery behaviour |
|---|---|---|---|
| Single rate | None | Not needed | Store spare solar only; no point charging from the grid |
| Economy 7 / Economy 10 | Set hours at night (and, for Economy 10, some afternoon or evening hours) | A two-rate meter or smart meter | Charge in the fixed window; run the house by day |
| Fixed time-of-use | Set cheap and peak periods every day | Usually needed | Charge in the cheap period; avoid drawing from the grid at the peak |
| Dynamic | Change with the wholesale market, often by the half-hour | Needed | The charging schedule has to follow the prices day by day |
How much of your use is already cheap?
Ofgem's typical consumption values assume Economy 7 households use 58% of their electricity by day and 42% at night. For a medium-use multi-rate meter (3,400 kWh a year) that is roughly 5.4 kWh a day outside the night window. That figure, not the battery's size, is the most a grid-charged battery could usefully move each day.
For single-rate homes there is no standard split. If you are considering a switch, look at your own pattern in a smart meter app: the evening share is what a battery would carry.
Charging windows and battery power
A short cheap window limits how much a battery can take in, because charging power is capped in kW. If the cheap hours are short, check that the battery's charging rate lets it fill its usable capacity within them. kW and kWh explains the arithmetic.
Before you rely on a tariff
- Read the terms. Some tariffs are designed around particular equipment, such as electric vehicles, and their terms may not say a home battery can charge at the cheapest rate.
- Check the meter. Most time-of-use and dynamic tariffs need a smart meter that sends half-hourly readings.
- Remember the switch affects everything. Moving from a single rate to a time-of-use tariff changes the price of all your use, not only what the battery shifts.
- Match the battery's schedule to the tariff, and change it if the tariff changes.
This guide stays with types and energy. Whether a particular tariff suits your home depends on its prices, which change and which you should compare with your supplier's current offers. For the kWh a battery could move on your figures, use the helper on a battery without panels; for exporting, see exporting from a battery.
Tariffs and solar batteries in winter
With panels, a battery often has little spare solar to store between November and February. A time-of-use tariff gives it another source in those months: the cheap hours. Some households use the battery for solar in summer and for cheap-rate grid charging in winter. The seasons guide shows why the gap opens.
Signs a battery and tariff are badly matched
- The battery is still charging when the cheap hours end, because its charging power is too low for the window.
- The battery is empty well before the dear hours finish, because your evening use is larger than its usable size.
- The battery is rarely emptied, because your use outside the cheap hours is smaller than its usable size.
- On a dynamic tariff, the schedule was set once and never follows the moving cheap hours.
Each of these shows up in a monitoring app within a few weeks. The first is about kW; the second and third are about kWh; the fourth is about settings. None needs a new battery to fix, but the second and third are worth knowing about before choosing a size, which is what the sizing helper is for.
Checking the schedule when the clocks change
Charging windows are set by the clock, and some systems don't move them automatically when British Summer Time starts or ends. Check in the app after each change that charging still starts and stops at the tariff's cheap hours. It takes a minute and avoids a week of charging at the wrong time.
If you are choosing between tariff types for the first time, the Citizens Advice guide linked below sets out the differences in plain terms, and your supplier can tell you which types your meter supports.
Tariff types also change over time as suppliers launch and withdraw products, so treat any list of options, including this one, as a starting point to check against what is on offer when you switch.
What this page is based on
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