Home Battery Sizes UK: 5kWh, 10kWh, 13.5kWh & 16kWh Compared
Home batteries come in a handful of standard sizes — and picking the wrong one is the most common (and expensive) mistake. Here’s what each kWh size actually covers, what it costs fitted, and which one suits your home.
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All home battery sizes compared
Battery size is measured in kilowatt-hours (kWh) — how much electricity it can store. For context, the average UK home uses around 8–12kWh a day, and roughly half of that is used in the evening and overnight when the sun isn’t shining. That evening-and-overnight chunk is what a battery is really there to cover.
| Size | Best for | Covers | Fitted cost (0% VAT) |
|---|---|---|---|
| ~5 kWh | 1–2 people, low usage, small solar | A light evening | £3,500 – £5,500 |
| ~10 kWh | Typical 3–4 bed family — most common | Evening + overnight | £5,000 – £8,500 |
| 13.5 kWh | Higher-usage homes, bigger arrays | Evening + overnight with headroom | £8,000 – £11,500 |
| 15–16 kWh+ | EV / heat pump / off-peak shifting | Full day of heavy use | £12,000 – £16,000 |
Notice the price per kWh falls as the battery gets bigger — a 10kWh unit is rarely twice the price of a 5kWh one. That’s why undersizing to save money often backfires: you pay a higher rate per kWh for a battery that still runs out. For the full price picture see our solar batteries UK guide.
5kWh batteries — the small home size
A 5kWh battery stores enough for a light evening: lights, TV, fridge, broadband, a bit of cooking. It suits one or two people using around 5–7kWh a day, or a home with a small 2–3kW array that simply doesn’t produce much surplus to store. Many 5kWh units are modular — Fox ESS and Pylontech both sell stackable modules, so you can start at 5kWh and add another later.
The catch: for a typical family home a 5kWh battery fills by mid-morning on a sunny day and is empty by 9pm. You end up exporting solar you could have stored, then buying grid power at night — the worst of both worlds. If you’re borderline, size up.
10kWh batteries — the sweet spot
This is the size most UK homes end up with, and for good reason. Around 10kWh covers a typical 3–4 bedroom family’s evening and overnight usage, pairs naturally with a 4–6kW solar array, and hits the best price per kWh. It’s also the size at which an off-peak tariff starts to pay: charge cheaply overnight, run the house on it all day.
The popular options here are GivEnergy (9.5kWh), Sunsynk (~10kWh), Fox ESS (two 5.2kWh modules), Puredrive and SolaX. See how they stack up in our best solar batteries roundup. If you’re pairing with a specific array, our 5kW solar with battery and 4kW solar with battery guides cover the whole-system cost.
Is 10kWh right for your home — or too much?
A free survey sizes your battery from your actual bills and roof, not a rule of thumb.
Find Out What Battery Size I Need →13.5kWh batteries — the Powerwall size
13.5kWh is the capacity of the Tesla Powerwall 3, which is why it’s become a size in its own right. It suits higher-usage homes — bigger families, home workers, anyone running a hot tub or electric showers — and homes with a 6kW+ array producing plenty of surplus to store. It also gives useful headroom if you want backup during power cuts, since you’re less likely to be running on empty when the grid drops.
Alternatives at this size include the myenergi libbi (modular up to 20kWh), Enphase and SolarEdge — all covered in our reviews. For the very largest whole-system builds see our 10kW solar with battery guide.
15–16kWh+ batteries — big arrays, EVs and heat pumps
Above 15kWh you’re into territory that only makes sense if you can fill it and empty it regularly. That means one or more of: a large 8–10kW+ array, an EV charged at home, a heat pump pushing electricity demand up sharply in winter, or a cheap overnight tariff you’re using to charge the whole thing every night and run the house off it. In those homes a big battery pays back well. In an ordinary home it spends half the year half-empty.
Most large systems are built by stacking modules — three or four 5kWh units, or two 8–10kWh units — rather than one giant box, which also makes them easier to add to an existing solar system in stages.
Which brands make which size
| Brand | Typical sizes | Modular? | Our review |
|---|---|---|---|
| GivEnergy | 5.2 / 9.5 / 13.5 kWh | Yes | GivEnergy review |
| Fox ESS | 5.2 kWh modules (stack to 20+) | Yes | Fox ESS review |
| Tesla Powerwall 3 | 13.5 kWh | Stack whole units | See best batteries |
| Sunsynk | ~5 / ~10 kWh | Yes | Sunsynk review |
| Pylontech | 3.5 kWh modules (stack) | Yes | Pylontech review |
| myenergi libbi | 5 kWh modules (to 20 kWh) | Yes | libbi review |
| SolaX | ~5.8 kWh modules (stack) | Yes | SolaX review |
| Puredrive | 5 / 10 kWh | Yes | Puredrive review |
| Enphase | 5 kWh units (stack) | Yes | Enphase review |
| SolarEdge | ~10 kWh | Yes | SolarEdge review |
| Duracell | ~5 kWh modules | Yes | Duracell review |
Two things to check on any datasheet. First, usable capacity — modern lithium iron phosphate (LFP) batteries give you 90–100% of the headline figure, but older chemistries held some back. Second, whether it’s AC or DC coupled, which matters for how it connects to your existing inverter. Sizes are indicative and change as ranges update; always confirm on your quote.
Matching battery size to your solar array
A useful installer rule of thumb: battery kWh ≈ 1.5 to 2.5 × your array size in kW. So a 4kW array pairs with roughly 6–10kWh, and a 6kW array with 9–15kWh. That ratio captures most of your daytime surplus without paying for storage you’ll never fill.
| Solar array | Annual output (approx.) | Suggested battery |
|---|---|---|
| 3 kW | ~2,550 kWh | 5 kWh |
| 4 kW | ~3,400 kWh | 8–10 kWh |
| 5–6 kW | ~4,250–5,100 kWh | 10–13.5 kWh |
| 8–10 kW | ~6,800–8,500 kWh | 13.5–20 kWh |
Lean towards the bigger end if you have an EV, a heat pump, or a cheap off-peak tariff. Lean smaller if you’re out all day and use little in the evening. And if you have no solar at all, sizing works differently — a battery charged purely on off-peak electricity is sized to your whole daytime usage; see home battery storage without solar.
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Find Out What Battery Size I Need →Sizing mistakes to avoid
Don’t
- Size to your total daily use — you only need to store what you use when the sun’s down
- Undersize to save money — you pay more per kWh and still run out
- Oversize with a small array — a battery you can’t fill never pays back
- Ignore your tariff — off-peak charging changes the maths completely
Do
- Check a year of bills — winter and summer usage differ a lot
- Buy modular if unsure — start at 5–10kWh and stack later
- Plan for the EV or heat pump you’ll have in three years, not just today
- Get it surveyed — an installer sizes from your real data
One more thing worth knowing: a bigger battery cycled gently tends to last longer than a small one hammered to empty every night. Slight oversizing within reason is kinder to the battery than chronic undersizing. Many installers now bundle panels, inverter and battery together — see our solar and battery packages guide for what a sensible bundle looks like.
The bottom line
For most UK homes, 10kWh is the answer. It covers a typical family’s evening and overnight, pairs well with a 4–6kW array, hits the best price per kWh and unlocks off-peak tariff savings. Go 5kWh only if you’re a small, low-usage household. Go 13.5kWh+ if you have a big array, an EV, a heat pump or you’re charging cheaply overnight and running the house on it.
But those are the bands, not your number. The right size comes from your actual bills, your roof and your tariff — which is exactly what a free home survey works out. Size it right once and the battery pays for itself; size it wrong and it’s the most expensive thing on the wall.
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Home battery sizes: frequently asked questions
What are the standard home battery sizes in the UK?
Most UK home batteries fall into four bands: around 5kWh (small), around 10kWh (the most common), 13.5kWh (Tesla Powerwall territory) and 15–16kWh+ (large or stacked systems). Many brands are modular, so you can stack units — for example two 5kWh modules — to reach the size you need.
What is the most common home battery size in the UK?
Around 10kWh. It’s the sweet spot for a typical 3–4 bedroom home using roughly 8–12kWh of electricity a day: big enough to cover the evening and overnight, without paying for capacity you’d rarely fill.
How much does each battery size cost fitted?
Typical 2026 UK installed prices with 0% VAT: about £3,500–£5,500 for 5kWh, £5,000–£8,500 for 10kWh, £8,000–£11,500 for 13.5kWh and £12,000–£16,000 for 16kWh. That works out at roughly £500–£800 per usable kWh, and the price per kWh generally falls as the battery gets bigger.
Is a 5kWh battery big enough?
For a small or low-usage household — one to two people, using around 5–7kWh a day — often yes. For a typical family home it’s usually too small: it fills quickly on a sunny day and runs out early in the evening, leaving you buying grid power anyway. Most families are better served by 10kWh.
Can you have a battery that’s too big?
Yes. If your solar array can’t fill it and you don’t use a cheap off-peak tariff, a large battery spends much of the year half-empty and the extra capacity never pays for itself. A big battery only makes sense with a big array, a cheap overnight tariff to charge from, or high evening demand such as an EV or heat pump.
What size battery do I need for a 4kW solar system?
Usually 8–10kWh. A 4kW array generates around 3,400kWh a year, and a battery of roughly 1.5 to 2.5 times the array size in kW (so 6–10kWh) captures most of the daytime surplus without being oversized. If you’re on an off-peak tariff or have an EV, lean towards the top of that range.
Figures are typical 2026 UK estimates for guidance only; battery capacities, usable capacity, prices and suitability vary by brand, model, installer and your household’s usage and tariff. 0% VAT on battery storage applies until 31 March 2027 per HMRC. Always get a tailored assessment from an MCS-certified installer. Sources: manufacturer specifications and UK installed-price data.