Battery storage
Home battery storage, explained plainly
Storing your own generation for the hours you actually use it — how sizing works, what tariffs change, and how to judge whether a battery is worth it for your household.
What a battery actually does
Solar generation peaks in the middle of the day. Most households use the most electricity in the morning and the evening. A battery bridges that gap: surplus generation charges it during the day, and the home draws from it later instead of buying electricity at the full unit rate.
Without storage, surplus generation is exported to the grid. Export is worth something on an export tariff, but usually less than the rate you pay to import. The value of a battery therefore comes from shifting your own generation into the hours you use it, rather than from generating more.
What a battery changes
- More of your own generation is used in the home instead of exported
- Evening and overnight consumption can be met from stored generation
- On some tariffs, cheaper off-peak import can be stored for peak hours
- Generation itself does not increase — only how the output is used
Through the day
Where a battery fits in a household's day
Midday
Generation is at its highest while the house is often using less. The surplus charges the battery instead of being exported.
Evening
Generation falls as household use rises. The battery supplies stored electricity, so less is bought from the grid.
Through the day
Daylight
Daylight reaches the panels on your roof.
Panels + inverter
DC generation is converted to usable AC.
Your home
Your home uses whatever it needs first.
Battery
Surplus can charge storage instead of exporting.
Evening and overnight
Battery
Stored electricity is released after dark.
Your home
Evening use is met from storage where possible.
Grid
The grid covers anything still needed.
Whether surplus generation is stored or exported depends on your system design, battery capacity and how your home uses electricity at the time.
Sizing a battery to your home
Usable capacity should reflect your evening and overnight consumption and the surplus your array actually produces — not simply the largest unit available. Oversizing means paying for capacity you rarely cycle. Undersizing means exporting surplus you could have stored and used.
Two other numbers matter alongside capacity: the continuous power output, which determines what the battery can run at once, and the round-trip efficiency, since a small proportion of stored energy is lost in charging and discharging. Where a household has an EV or a heat pump, the shape of that demand changes sizing significantly.
Batteries and electricity tariffs
Some tariffs make it worthwhile to charge from the grid at cheaper overnight rates as well as from solar, then run the house from the battery during expensive periods. Whether that helps depends on the specific tariff, the price differential and your usage pattern, so it is something to review with your own figures rather than assume.
Export arrangements matter in the other direction: a generous export rate reduces the gap a battery is closing. This is why we look at import rate, export rate and consumption pattern together.
Power cuts and backup supply
A standard grid-tied battery does not automatically keep your home running during a power cut. Backup requires equipment specified for it, along with a switching arrangement that safely isolates your home from the network, and it usually supports a defined set of circuits rather than the whole house.
If resilience is a priority for you, say so early: it affects inverter selection and wiring design, and it is far simpler to plan at design stage than to retrofit.
Adding a battery later
A battery can be added after your solar installation. Planning for it at design stage keeps that upgrade straightforward — inverter choice, available space, cable routes and the grid connection notification all follow from it, so we confirm your intentions before finalising a design even if you are not buying storage now.
When a battery is worth it — and when it isn't
Storage tends to make most sense for households with meaningful evening and overnight usage, a reasonably sized array producing genuine surplus, a tariff that rewards load shifting, or a specific interest in resilience.
It adds less where most consumption already happens in daylight hours, where the array is small enough that little is exported, or where the roof cannot support enough generation to charge the battery regularly. A battery is optional, and if your usage pattern means it adds little, we will tell you.
Battery storage FAQs
Do I need a battery?
No — solar works perfectly well without one. A battery matters if a lot of your electricity use happens outside daylight hours, because it stores surplus generation for the evening instead of exporting it. If you are at home during the day and already use most of what you generate, a battery adds less. We look at your usage pattern before suggesting one either way.
What size battery do I need?
Battery sizing is driven by how much electricity you use outside generation hours, your annual consumption, the size of your array, any EV or heat pump, your tariff and whether you want backup capability. A common domestic range is roughly 5–15 kWh of usable capacity, but the right figure is the one you can genuinely cycle most days. Bigger isn't automatically better: capacity that sits unused still costs money.
Can a battery power my home at night?
It can supply your home in the evening and overnight until the stored energy is used up. Whether it covers the whole night depends on usable capacity, how much surplus was stored that day and what you are running — a fridge, lighting and a television draw far less than an oven, immersion heater or EV charger.
Can a battery charge from the grid?
Most modern home batteries can charge from the grid as well as from solar. On a time-of-use tariff with cheaper off-peak periods, that lets you fill the battery when electricity is cheapest and use it at peak times. Whether it is worthwhile depends entirely on your tariff and consumption, so it should be assessed rather than assumed.
Will a battery work in a power cut?
Not automatically. Many solar and battery systems shut down during a grid outage for safety reasons. Backup during a power cut requires equipment and wiring designed for it — typically a battery and inverter with backup capability plus a separate protected circuit or changeover arrangement, which is usually specified as an option rather than included by default. If outage backup matters to you, say so before design so it can be quoted properly.
Can I add a battery later?
Usually yes. A battery can be retrofitted to an existing solar installation, typically using an AC-coupled battery with its own inverter, or a DC-coupled battery where a hybrid inverter was installed at the outset. Planning for storage at design stage keeps the later upgrade simpler and can avoid replacing the inverter, so it is worth telling us your intentions early.
How long does a battery last?
Home batteries are usually warranted for a set number of years or cycles — commonly around 10 years, often with a stated end-of-warranty capacity such as retaining a defined percentage of original capacity. Real-world life depends on how deeply and frequently the battery is cycled, and on temperature. Specific figures depend on the product specified for your system.
Do I need solar to have a battery?
No. A battery can be installed on its own and charged from the grid on a time-of-use tariff, then discharged at peak times. Paired with solar, though, it does two jobs — storing your own free generation and shifting grid purchases — which is why the two are so often installed together.
Start with your roof, then size your battery
Your roof assessment and electricity usage together determine whether storage is worth adding.