Why storage changes the economics
Solar panels decide how much you generate; a battery decides what happens to it. Without storage, surplus power exports to the grid for 5p–15p per unit and you buy it back in the evening at ~24p. With storage, your daytime generation waits until you actually need it. For most solar homes that single change is the difference between a good investment and a great one.
Batteries also unlock time-of-use tariffs. Charge overnight at off-peak rates, discharge through the expensive evening peak, and the battery earns money every single day — sunshine optional. That's why battery-only installations are one of the fastest growing things we fit.
Systems we install
- Sigenergy SigenStor — the stackable tower we fit most: start at 8 kWh, expand module by module, with built-in hybrid inverter and optional backup.
- Tesla Powerwall — the household name, with whole-home backup capability.
- FoxESS & AlphaESS — excellent value LFP systems, ideal when pairing storage with a new solar installation.
- EcoFlow — flexible options where space or portability matter.
Everything we fit uses LFP chemistry — safer and longer-lasting than older NMC cells — and carries a 10-year warranty as standard.
Retrofit or new install
Already have solar? An AC-coupled battery bolts onto almost any existing system, whoever installed it. Starting fresh? A hybrid inverter running panels and battery together is usually the cleanest, most efficient design. Installation is typically completed within a day for retrofit, or as part of a 2-day combined install.
How much does a home battery cost?
Pricing depends on capacity, chemistry and whether you need backup capability. As a rough guide for what we typically fit in North West homes in 2026:
| Capacity | Typical use case | Indicative installed cost |
|---|---|---|
| 5 kWh | Small terrace, low daily usage, starter system | £3,500 – £4,800 |
| 10 kWh | Average 3-bed semi — covers evening & overnight | £4,800 – £6,500 |
| 15 kWh | 4-bed detached, EV charging, all-electric heating | £6,200 – £8,500 |
| 20 kWh | Larger detached, heat pump home, off-peak arbitrage | £7,500 – £10,500 |
| 25–60 kWh | Stackable expansion for heat pump + EV + tariff maxing | from £9,500 |
Prices assume retrofit into an existing solar system. New solar + battery installs are quoted together — see the savings calculator for a combined indicative number for your home. 0% VAT applies to domestic battery installations, whether retrofit or bundled with solar.
Sizing worked examples
Battery sizing isn't about matching your solar array — it's about matching your evening and overnight usage. Two examples we quote every week:
3-bed semi in Wigan, 2,900 kWh/year, gas-heated: around 8 kWh of usage falls in the peak window (16:00–19:00). A 10 kWh battery covers that plus overnight standby and leaves ~2 kWh headroom for arbitrage on a smart tariff. Payback vs a solar-only install typically drops from ~7 years to ~5.5 years once the battery is included.
4-bed detached in Warrington, EV plus heat pump, 8,500 kWh/year: peak-window demand climbs to 14–18 kWh once you include hot-water reheat and evening heating. A 15–20 kWh stack is the right target. On Octopus Cosy or Intelligent Go the battery earns money even before you count solar self-consumption — nightly off-peak charge, peak discharge, repeat.
Oversizing beyond your actual peak-window demand adds cost without saving anything. That's why we size from your half-hourly usage data (from your smart meter or your bills) rather than a rule of thumb.
SigenStor, Powerwall or FoxESS — how they compare
The three systems we fit most, side by side:
| System | Chemistry | Modular capacity | Warranty | Backup | Best for |
|---|---|---|---|---|---|
| Sigenergy SigenStor | LFP | 8 kWh modules, stackable to 48+ kWh | 10 years / ~6,000 cycles | Optional | Homes that will grow — heat pump, EV, extensions |
| Tesla Powerwall 3 | LFP | 13.5 kWh single unit, up to 4 stacked | 10 years / unlimited cycles for solar self-consumption | Whole-home included | Anyone who wants seamless whole-home backup and a household name |
| FoxESS EP / EQ | LFP | 5.2 kWh modules, stackable to ~30 kWh | 10 years | Optional gateway | Value-focused installs bundled with a new FoxESS solar system |
All three are LFP — safer chemistry, no thermal runaway risk, and no capacity cliff at end of warranty. The right answer depends on your growth plans (SigenStor wins on expansion), whether backup is a hard requirement (Powerwall wins on seamlessness) and your total budget (FoxESS wins on £/kWh when installed with a matching inverter).
Battery + smart tariff — where the extra saving comes from
On a flat 24p/kWh tariff a battery only saves what you'd otherwise export at 5–15p. On a time-of-use tariff — Octopus Go, Cosy, Intelligent Go, or E.ON's Next Drive — you charge overnight at 7–9p and either discharge through peak hours or run your appliances direct from the battery. That gap is around 15p per kWh, or £1.50 a day per 10 kWh of usable capacity shifted. Over a year, a 10 kWh battery on a smart tariff typically adds £300–£500 of saving on top of the solar self-consumption uplift.
The other lever is export arbitrage during long summer days: fill the battery from solar in the morning, sell what the panels generate all afternoon back to the grid at SEG rates. Small margin per unit but it stacks up on sunny weeks.
Find the right size for your home
We model your usage and tariff before recommending a single kWh. Free, no obligation.
Get a free quote todayBattery storage FAQs
What size battery do I need?
The average UK home uses 8–10 kWh of electricity a day, so a 10 kWh battery is a common starting point. Modern stackable systems run from 5 kWh to 60 kWh — you can start small and add modules later as your needs grow. Sizing is based on your peak-window (16:00–19:00) usage rather than daily total.
Is a battery worth it without solar panels?
Often, yes. On a smart time-of-use tariff a battery charges overnight at cheap rates and powers your home through expensive peak hours. This tariff arbitrage alone can justify the system — we run the numbers for your usage before recommending anything.
Can I add a battery to my existing solar system?
In most cases, yes. An AC-coupled battery works alongside almost any existing solar installation regardless of inverter brand. We confirm compatibility during your survey.
Will a battery keep my power on in a power cut?
With a backup gateway fitted, yes — systems like the Sigenergy SigenStor and Tesla Powerwall can keep essential circuits running during an outage. Backup is optional and we design it in from the start if you want it.
How long do home batteries last?
Modern LFP (lithium iron phosphate) batteries are rated for thousands of cycles and typically carry 10-year warranties, usually guaranteeing at least 70–80% of original capacity at the end of the warranty period. LFP batteries have no thermal runaway risk, making them safer than older NMC chemistry.
How is a battery installed and where does it go?
Most home batteries are wall-mounted in a garage, utility room, loft or a weather-rated outdoor location. They are around the size of a small radiator per 10 kWh of capacity. A retrofit installation typically takes a single day; a fresh solar + battery install is 2 days.
Is there VAT on home batteries?
No. From February 2024, 0% VAT applies to domestic battery installations in the UK — whether retrofit to an existing solar system or installed standalone. This is an extension of the same relief that already covered solar and heat pumps.
What is the payback on a home battery?
Retrofit batteries paired with a smart tariff typically pay back in 6–9 years, extending well within the 10-year warranty. Bundled solar + battery installs pay back in 5–8 years total. Payback depends on your peak usage, tariff choice, and whether you have solar.
Related guides: Battery storage: what to know before buying ·Is solar PV still worth it?