A household generating surplus solar power at lunchtime but buying electricity again at 6pm is paying for energy it may already have produced. This battery storage savings example shows how a home battery can change that pattern, using realistic UK assumptions rather than headline figures.
The exact result will vary with your roof, electricity tariff, household routine and the system quoted. However, working through the numbers makes it much easier to judge whether battery storage is likely to earn its place in your home.
A battery storage savings example using solar panels
Consider a typical family home in South Wales with a 4kW solar PV system and annual electricity use of 3,800kWh. The panels generate around 3,700kWh a year. Without a battery, the household uses 1,400kWh of that solar power directly during the day and exports the remaining 2,300kWh to the grid.
For this example, assume the home pays 28p per kWh for imported electricity and receives 15p per kWh for exported solar electricity. These are illustrative figures, not guaranteed tariffs. Your installer or energy supplier can help you check current rates before you decide.
Without battery storage, the annual value of the solar electricity looks like this:
- 1,400kWh used in the home avoids buying electricity at 28p, saving £392.
- 2,300kWh exported at 15p earns £345.
That gives a total annual benefit of approximately £737 from the solar panels.
Now add a 5kWh battery. Not every unit of surplus solar can be stored and used later: there are round-trip losses, and the battery will sometimes already be full. A well-sized battery might allow the household to retain and use a further 1,400kWh of solar power across the year.
That 1,400kWh would otherwise have been exported for 15p, producing £210 in export payments. Used later in the home, it avoids 1,400kWh of imported electricity at 28p, worth £392. The battery’s additional annual value is therefore about £182 in this simple solar-shifting calculation.
The total solar benefit rises from around £737 to around £919 a year. The figure that matters when assessing the battery is the difference – in this case, roughly £182 a year – rather than the full value of the solar installation.
Why the simple calculation is not the whole story
£182 is a useful starting point, but it can understate or overstate the likely benefit. Batteries are not only used to move excess solar from daytime to evening. With the right electricity tariff, they can also charge when grid electricity is cheaper and supply some of your home use when prices are higher.
For example, imagine the same household can buy off-peak electricity at 10p per kWh and avoids importing at 28p per kWh later in the day. After allowing for battery losses, each stored kWh can still create a worthwhile saving. If the battery supplies an extra 1,000kWh a year from cheaper overnight charging, the tariff-related saving could be in the region of £140 to £160, depending on battery efficiency and how consistently the household follows the tariff window.
Combined with solar shifting, that could bring the annual battery benefit closer to £320 to £340. It is not automatic, though. The tariff must suit your lifestyle, the battery controls need to be configured correctly, and you need enough evening or morning electricity demand to use the stored energy.
A battery does not create free electricity. It helps you buy less electricity at the most expensive times and make better use of the electricity your panels already generate.
What might payback look like?
Suppose the installed cost of the 5kWh battery in this example is £4,500. At £182 a year of savings from solar shifting alone, the simple payback period would be long – almost 25 years. At a more favourable £330 a year, where a suitable time-of-use tariff adds value, simple payback falls to around 14 years.
This is why broad claims about a battery “paying for itself” in a set number of years should be treated carefully. Battery prices, system sizes, tariffs and household habits differ significantly. A household that is empty all day, has high evening use and charges an electric vehicle overnight may have a very different result from a couple with modest electricity use.
It is also worth looking beyond simple payback. A battery may reduce exposure to peak electricity prices, provide a degree of energy independence and, where specified, offer backup power during a power cut. Backup capability is not standard on every system and can add cost, so it should be discussed as a feature you genuinely need rather than assumed as part of every quote.
The factors that change your savings most
Your annual electricity consumption is central. Homes using more electricity after sunset generally have more opportunity to use stored solar power. Households with a heat pump, electric vehicle or electric cooking may have greater potential, but only if the battery size and tariff are planned around those loads.
Solar generation matters too. A small array with limited surplus in summer may not justify a large battery. Equally, fitting a battery that is too small can mean it fills early and exports useful solar energy anyway. The best fit is usually based on half-hourly usage data, estimated solar generation and the tariff you expect to use.
Export rates can make a noticeable difference. When export payments are relatively generous, giving up an exported unit of solar power to store it is less valuable. The battery needs to replace a more expensive imported unit later for the calculation to work in your favour.
Battery efficiency and degradation should also be part of the conversation. A battery does not return every kWh put into it, and usable capacity can reduce over time. Reputable quotes should state the usable capacity, warranty length, expected throughput and any conditions attached to the warranty. Comparing the headline battery size alone can be misleading.
Making your battery storage savings example more accurate
Before accepting a quotation, ask for a personalised estimate that separates solar-panel savings from battery savings. This prevents the total benefit of the full system being presented as if it all comes from the battery.
A useful proposal should explain the assumed import and export tariffs, annual electricity use, estimated solar generation, direct solar use and battery cycling. It should also make clear whether savings from an off-peak tariff are included. If they are, check that the tariff is available to you and that its higher daytime rate will not outweigh the expected gains.
You can improve the estimate by gathering a year of electricity bills, or smart-meter data if available. Note when your household uses power: early mornings, weekday evenings, weekends and winter are particularly relevant. If you are planning an electric vehicle, heat pump or extension, mention it. A battery sized for today’s usage may not be right for next year’s household.
For homeowners in Cardiff, Newport, Swansea, Bristol and nearby areas, local shading, roof orientation and installer experience can affect the solar side of the calculation. Requesting more than one detailed proposal helps you compare assumptions as well as prices. An MCS-accredited installer should be able to explain their figures in clear terms and show where the uncertainty lies.
Is a battery right for your home?
Battery storage is often most compelling for households with solar panels, meaningful evening demand and access to a tariff that rewards flexible energy use. It may be less compelling where electricity consumption is low, the home already uses most solar power directly, or the installation cost is high relative to likely annual savings.
The most reassuring route is to compare like-for-like quotes from vetted, MCS-accredited installers and ask each one to model your actual usage. Solar Planet can help simplify that comparison by connecting you with local installers, so you can focus on the figures, warranty and system design that make sense for your property.
A good battery decision should feel clear rather than rushed: choose a system because its assumptions stand up to scrutiny and its benefits match how you genuinely use energy at home.
