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Guide · Home energy

Home batteries without solar panels

A battery can charge when electricity is cheaper and power your home later. Whether that saves money depends on the gap between your cheap and standard rates, how much you use outside the cheap period, and the battery’s cost and losses.

By energy.org.uk editorial team · Reviewed by energy.org.uk editorial team · Published and updated 2 October 2026

Who this is useful for

  • Households without solar panels, including flats and homes with unsuitable roofs, that are thinking about a battery.
  • People already on, or considering, a tariff with a cheaper overnight or off-peak period.
  • Anyone with a battery quote who wants to check the saving it claims.

If you have solar panels or are planning them, use the solar battery calculator instead. It works out the value of storing your own solar electricity.

How it works

  1. Your tariff has a cheaper period, often overnight.
  2. The battery charges from the grid during that period.
  3. When the cheap period ends, your home uses the stored electricity before buying any at the standard rate.
  4. Once the battery is empty, you buy from the grid as normal.

Some energy is lost going in and out of the battery. Roughly, each kWh the battery supplies saves:

standard rate − (cheap rate ÷ round-trip efficiency)

At 90% efficiency, electricity bought at 8p costs about 8.9p by the time the battery delivers it. If your standard rate is 28p, each kWh used from the battery saves about 19p.

When savings may be small or negative

  • You have a single-rate tariff. There is no cheaper period to charge in. Because of storage losses, running the battery would cost money.
  • The price gap is small. If the standard rate is barely higher than the cheap rate divided by the efficiency, there is little to gain.
  • You use little electricity outside the cheap period. A battery can only replace electricity you would otherwise buy at the higher rate. A small household may not empty a large battery each day.
  • The tariff costs more in other ways. A time-of-use tariff can have a higher standing charge or a peak rate above your current single rate. Work out the effect of changing tariff separately from the effect of adding a battery.
  • The installed cost is high compared with the saving. The payback can be longer than the battery lasts. Energy Saving Trust gives a typical battery lifespan of about 10 to 12 years.
  • Standby use and ageing. Batteries and inverters use a little electricity themselves, and usable capacity falls over time.

Why size, use, charging window and tariff conditions matter

  • Usable capacity in kWh is what the battery can actually supply. Quotes sometimes give a larger total capacity.
  • Power in kW limits how fast it charges and discharges. It decides how much the battery can fill in a short cheap period, and whether it can meet high-power demands such as an electric shower.
  • The charging window. A 3 kW battery can take in at most 12 kWh in a four-hour window, before losses.
  • When you use electricity. Evening and daytime use outside the cheap period is what a battery replaces. Your smart meter data shows this better than any typical pattern.
  • Tariff conditions. Some time-of-use tariffs are only for electric-vehicle drivers or heat-pump owners. Most need a smart meter sending half-hourly readings. Check contract length, exit fees and how the rates can change.
  • Export. Do not assume you can sell grid-charged electricity. The Smart Export Guarantee pays for eligible renewable exports, and supplier rules on battery exports differ. Our calculator does not count any export income.

Calculator

Home battery calculator

Do you have a cheaper overnight electricity rate?
Roughly how much electricity do you use?

Typical: 2,700 kWh a year (Ofgem typical use)

Are you mainly home during the day or evening?
Do you have a battery quote?

Answer the first question to see your estimate.

Change assumptions

Defaults are planning assumptions. A quote or your bill should replace them.

How this estimate works

We split a typical day into half-hours, using a simple shape with low use overnight and peaks in the morning and evening. Use rises in winter and falls in summer.

Each day the battery charges only in the cheap period and is used only outside it. It can deliver the smallest of: its usable capacity; what its power can put in during the cheap period; and your use outside the cheap period, each half-hour limited by its power.

Storage losses are counted once: to deliver 1 kWh at 90% efficiency, the battery buys about 1.11 kWh at the cheap rate. If that costs more than the standard rate, we assume the battery is left idle, as a sensibly set-up battery would be.

Standing charges are included, so a tariff with a higher standing charge shows up in the “changing tariff” line, not as a battery saving. Real savings depend on the battery’s controls, standby use, ageing and how your use varies day to day.

Sources: Ofgem typical domestic consumption values; Energy Saving Trust: battery storage.

Have solar panels or planning them? Use the solar battery calculator. New to home batteries? Read the guide.

Open the home battery calculator →

Power cuts: backup is not automatic

Energy Saving Trust says most battery storage systems will not provide power during a power cut. Backup needs equipment designed and installed for it. That means a battery or inverter with a backup function, plus wiring that safely separates the home, or some circuits, from the grid.

If backup matters to you, ask the installer which circuits it covers, how much power it can supply, how quickly it switches over, and whether it is included in the price.

What to check in a quote

  • Usable capacity and total capacity, in kWh.
  • Continuous power and short-term peak power, in kW.
  • Round-trip efficiency and standby electricity use.
  • An itemised price: battery, inverter, installation, electrical work, any consumer unit changes, and commissioning.
  • Where the battery will go, and the manufacturer’s limits on location, temperature and clearances.
  • Who notifies or applies to your electricity network operator.
  • How the battery will be set to charge in your tariff’s cheap period, and what happens if the tariff times change.
  • Whether backup during a power cut is included.
  • How the savings were worked out: which rates were used, whether the tariff change is shown separately, whether a full charge every day is assumed, and whether export income is included.
  • Which certification or consumer-protection schemes the installer belongs to, and how complaints are handled.

What to check in a warranty

  • How long it lasts in years, and any limit on energy throughput or cycles, whichever comes first.
  • The capacity guaranteed at the end of the warranty, as a percentage of the original.
  • Separate cover for the battery, inverter and workmanship, and who provides each.
  • What happens if the installer stops trading, and whether the workmanship guarantee is insurance-backed.
  • Conditions such as registration, an internet connection, servicing or operating temperature.

Important limitations

  • Our estimate uses a typical daily pattern. Your own half-hourly smart meter data gives a better answer.
  • Tariff rates change. A battery chosen for today’s price gap may save less if the gap narrows.
  • Simple payback leaves out finance costs, replacement, loss of capacity and future price changes.

Related tools and guides

Sources

Official sources checked 2 October 2026.