Five ways to have a battery
A home battery costs about £5,000–8,000 installed (Energy Saving Trust, August 2026). What it earns depends on what it stores: cheap overnight electricity, your own solar, or both — and whether you want it to keep the lights on in a power cut.
Keeps the whole house running in a power cut; needs a backup gateway with its own earthing. Above 20 kWh means more than one enclosure.
Money 0% VAT · the gateway, earthing and a held-back reserve all add to the cost
Backup reserve and switchover →Can’t use the new plug-in solar route: anything that stores power from a socket still needs an electrician to hardwire it.
Money 20% VAT on retail kits · no export payment
The plug-in rules →What decides your payback
There is no independent UK dataset of measured battery paybacks. What there is: the tariff gap, how much of the battery you actually cycle, and whether winter and backup eat into it.
Size it to what the house draws between the cheap window and bedtime — not to the biggest unit that fits. Spare capacity sits idle.
Read the answer →02How fast it charges and discharges. A 20 kWh battery on a 5 kW inverter still pulls from the grid when the house draws 7 kW.
Read the answer →03Six hours at about 8p against 26p in the day. Without solar, that gap is the whole business case.
Read the answer →04Cold slows charging — many batteries pause below 0 °C — and winter solar is a tenth of summer. The overnight rate carries the winter.
Read the answer →05Backup needs an EPS or a gateway, adds cost and holds back a reserve you can’t use day to day. Switchover isn’t always seamless.
Read the answer →The calculator has a dial for each of these, and a 24-hour chart of the battery earning its money.
Size your battery →Spot a bad install
PAS 63100 rules out lofts, bedrooms, hallways, landings and stairs. Outdoors or a garage first; indoors needs fire separation and a linked alarm.
Batteries don’t give backup by default. A few circuits need an EPS output; the whole house needs a gateway with its own earthing. If it isn’t on the quote, it isn’t happening.
A 20 kWh battery on a 5 kW inverter still pulls from the grid when the house draws 7 kW — and takes all night to fill. Size the inverter to your evening peak.
Never open an enclosure or touch DC wiring. Status lights and app alerts are for reading, not fixing — the error-code pages say which few checks are safe.
Compare the products the research covers
Only figures the research has checked. A dash means the source did not state it. No 'best buy' — the right product depends on the setup, the inverter and the installer. Every figure is dated and linked to its source below the table.
| Product | Usable capacity | Output and backup | Switchover | Rating | Warranty | Grid approval | Notes |
|---|---|---|---|---|---|---|---|
| Tesla Powerwall 3Tesla UK datasheet and warranty, 2026 · checked 24 September 2026 | 13.5 kWh | 3.68–11.04 kW AC (configurable); 5 kW charge, 8 kW with Expansion; backup needs Backup Gateway 2 | ‘Within a few seconds’ — no millisecond figure published | IP55 / IP67 | 10 years to 80% capacity; needs internet, else 4 years | G98, G99, G98/NI, G99/NI | <50 dB(A) typical; 130 kg; 37.8 MWh throughput cap outside listed uses |
| AlphaESS SMILE-G3 with BAT-10.1PAlphaESS installation and operation manual, August 2023 · checked 24 September 2026 | 9.6 kWh per battery | Backup 5 kW (S5) or 3.68 kW (S3.6) | <20 ms | — | — | — | Charges 0–50 °C; yellow LED patterns are binary error codes |
| Pylontech Force-H3Pylontech Force-H3 manual (via Ferroamp), 2025 · checked 24 September 2026 | 5.12 kWh per module (FH10050) | High-voltage; inverter sets output | Inverter sets backup | IP55 | — | Via the inverter | Solid orange status light = lost comms, over-current or module fault |
| Pylontech US5000Pylontech US5000 installation manual, September 2024 · checked 24 September 2026 | — | Low-voltage; up to 16 modules per group | Inverter sets backup | IP20 (indoors) | — | Via the inverter | Protects at 90 A, 44.5 V, above 60 °C or below −10 °C |
| GivEnergy Giv-Bat 9.5 Gen 3GivEnergy manuals and guides; ESS News, April 2026 · checked 24 September 2026 | 9.5 kWh (nominal, from the product name) | Via GivEnergy inverter; EPS optional | EPS about 5 s | — | Not honoured — GivEnergy Ltd in administration since 9 April 2026 | — | Charging pauses below 0 °C; portal and app still run (GivEnergy Software Ltd) |
| Sigenergy SigenStorSigenergy datasheets and TÜV SÜD compliance documents · checked 24 September 2026 | — | Controllers 3.0–6.0 kW single-phase; 2× nominal for 10 s off-grid | 0 ms claimed — only with Sigen gateway and a controller rated above the load; lab tested | — | — | G98 (3.0/3.6 kW), G99 (4.0–6.0 kW), TÜV SÜD 2023 | Stackable EV DC module 12.5 kW (25 kW licence); switchover makes a noise |
A dash means the research has not verified that figure yet — we leave it blank rather than copy a marketing page. Usable capacity, backup power and switchover time are the three numbers to compare against your own sizing.
Size your battery →VAT, loans and export payments
No battery grant exists. Every line below was checked on 24 September 2026; the detail and sources are on the question pages.
On installed batteries — with or without solar — until 31 March 2027, then 5%.
Government-backed low-interest loans from September 2026; up to £15,000 for a battery. Needs an MCS installer.
In England, a battery can be funded alongside solar where it helps, for owner-occupiers with EPC D–G and household income of £36,000 or less. Runs to March 2028.
SEG suppliers must pay for solar export but not for electricity you charged from the grid. Some tariffs pay peak rates for battery export; they can change.
Eligibility, availability and rates change — check the official source before you commit to work. This page does not assess eligibility or submit an application.
Should I export from my battery? →Written answers with their sources, checked 24 September 2026.
Size your battery →Already have a battery?
Temperature range, firmware, what a warranty needs from you and when capacity loss is normal.
Battery maintenance →Manufacturer meanings for more than 20 brands, and the few checks a homeowner can safely make.
Battery error codes →Seven questions give you a capacity range, the minimum inverter power, a 24-hour picture of the battery earning its money, and the payback — with dials for size, power and every price. Then compare quotes against it.
