Here's the answer nobody selling batteries will give you: it depends almost entirely on how you live. For some households a battery is clearly the right call. For others it's £3,000–8,000 spent making a spreadsheet look tidier. The good news is you can work out which camp you're in before spending anything.
The problem a battery solves
Solar panels generate most of their electricity around midday. Most households use most of theirs in the morning and evening. So without a battery, a typical home only uses roughly half of what its panels produce — the rest gets exported to the grid for a payment under the Smart Export Guarantee.
The catch is that export rates vary a lot between suppliers, and for most people a unit sold earns well under half of what a unit bought back that evening costs. A battery closes that gap: it stores your midday surplus and releases it in the evening, lifting your "self-consumption" — the share of your own solar you actually use — from roughly 50% to 80% or more.
The rough maths
Take a typical 4kW solar system in southern England, generating somewhere around 3,000–3,800 kWh a year. At current standard-tariff prices, the picture looks something like this:
| Solar only | Solar + battery | |
|---|---|---|
| Self-consumption | ~50% | ~80%+ |
| Typical annual saving | roughly £450–600 | roughly £700–900 |
| Typical payback | often 7–11 years | often 9–13 years |
These are honest ranges, not promises — your roof, your tariff and your habits all move the numbers. But notice two things. First, the battery does add real money, typically a few hundred pounds a year. Second, because the battery itself costs £3,000–8,000, it usually lengthens the overall payback rather than shortening it. Anyone telling you a battery pays for itself faster than the panels do is selling, not advising.
When a battery is genuinely worth it
The battery case gets stronger the more of these apply to you:
- You're home in the evenings. If your big usage is 6pm–11pm — cooking, heating, telly, hot water — a battery moves your free midday solar to exactly when you need it.
- You're on (or could switch to) a time-of-use tariff. Some tariffs offer much cheaper overnight electricity. A battery can charge cheap at night and discharge during expensive daytime hours — a second way to save that works even in winter, when solar is doing little.
- You have an EV. EV owners usually already have access to cheap overnight rates, which makes that night-charging trick more valuable, and their higher overall usage means the savings compound.
- You run air conditioning. AC works hardest in the evening and overnight — precisely when panels have stopped. A battery is what makes solar and AC actually work together; we've covered what size battery that takes separately.
When it probably isn't
Equally, be honest with yourself about these:
- Your usage is small. If your bills are modest — say a low-occupancy home using well under 2,500 kWh a year — there simply isn't enough spend to save your way out of. The battery will work fine; the maths won't.
- You're moving within a few years. A battery tends to add less to a sale price than it costs to install. If you'll be gone in three or four years, the numbers rarely recover.
- You're out all day and out most evenings. If nobody's home to use the stored energy, you're paying thousands to shift electricity you weren't going to use anyway.
- You'd be stretching to afford it. A battery is an optional upgrade, not a necessity. Solar alone still works — you'll just export more.
Degradation, honestly
Batteries wear out gradually. A modern home battery will lose some capacity over its life, and warranties generally run to around ten years or a set number of charge cycles, usually guaranteeing the battery still holds a decent majority of its original capacity at the end. That's fine — but it means your payback maths should treat the battery as a 10–15 year asset, not a forever one. If a quote's savings projection quietly runs 25 years on day-one performance, treat it with suspicion.
What it costs in 2026
A typical home battery of 5–10kWh costs £3,000–8,000 installed, depending on size and whether it goes in alongside solar (cheaper) or gets retrofitted later (dearer). Batteries fitted with solar currently benefit from 0% VAT, which rises to 5% after 31 March 2027 — a nudge, not a panic, but worth knowing if you're deciding this year versus vaguely someday.
The bottom line
A battery is worth it if you're home in the evenings, plan to stay put, and ideally can pair it with a time-of-use tariff, an EV or air conditioning. It's not worth it for small consumers, short tenures or empty houses. Run your own numbers off your actual bills — not a salesman's "typical household".
If you'd like a straight answer for your specific house, we'll match you with one vetted MCS-certified installer — one, not a call barrage — who'll quote it honestly. Start with a free estimate.