A battery without solar panels

By Daan Haket · researched and written with an AI assistant · updated 26 October 2026

Without panels, the saving this calculator looks at comes from one place: the gap between a cheap-hours rate and the rate you would otherwise pay. On a tariff with one rate all day, a battery on its own saves nothing on energy. Backup during a power cut is a separate reason to buy one, with its own equipment cost.

The sum

Each night the battery charges from the grid at the cheap rate and covers part of your evening use. Because some energy is lost in charging and discharging, every kWh you use from the battery costs cheap rate ÷ round-trip efficiency. The saving per kWh is the peak rate minus that. Try your own figures. This version has no solar or export fields:

Your home Electricity use per year (kWh)From your bill or supplier app. Prefilled with Ofgem’s typical (medium) use for a home on a single rate: 2,500 kWh. Your own bill is better. Share used in daylight hours (%)Your estimate; few people know it. 40 is only an example. Try 30 and 50 to see how much it moves the answer.

Your tariff Standard or peak unit rate (p/kWh)Prefilled with the Ofgem price cap average for Direct Debit, 1 October to 31 December 2026: 26.32p. Cheap-hours unit rate (p/kWh)Only if your tariff has cheap hours; otherwise leave it equal to the standard rate. See smart tariffs for checked rates.

The battery Usable capacity (kWh)From the datasheet. Example: 13.5 (GivEnergy All in One, checked). Round-trip efficiency (%)From the datasheet if stated. Example only: 90. Installed price (£)Your quote. Example only: 6500, inside the Energy Saving Trust range of around £5,000 to £8,000.

More detail (optional): cheap window, load shifting, warranty, loan

Cheap hours Length of the cheap window (hours)For example 5 for 00:30–05:30, 3 for 02:00–05:00. Only used together with the charging power below: the two together cap how much the battery can fill at the cheap rate. Battery charging power (kW)From the datasheet. Only used together with the cheap window above. Share of your use already in cheap hours (%)For example an EV or timed appliances. Example only: 0. Share of your evening use you could move to cheap hours yourself (%)Running the dishwasher, washing machine or car charger on a timer instead of in the evening, without a battery. We then show what that alone saves, and count only what the battery adds on top. Example only: 0.

Warranty and wear Warranty (years)We then tell you whether it pays back within the warranty. Yearly loss of saving (%)Allowance for capacity fade or tariff changes. Example: 0.

Paying with a loan Interest rate (% a year)From the loan or finance offer. Leave empty if you pay cash. Loan term (years)

VAT on a standalone battery

HMRC includes installing a standalone battery to store grid electricity.

“the installation of a standalone battery for storing electricity from the grid (the mains electricity);”

Source: gov.uk, read 19 October 2026

First check you qualify for a whole-home cheap rate

Some cheap rates only apply to electric-car charging, and the rest of the house stays on the normal rate. A battery needs a cheap rate for the whole home. Smart tariffs for battery owners lists who can join each one.