How long will a Sigenergy SigenStor last in a power cut?
A full Sigenergy SigenStor (8.76 kWh usable) runs the fridge-freezer, heating controls, broadband, lights and phones for about 2 days 22 h in a British home. Running the whole house as normal, it lasts about 26 h 7 min.
Starting at a 20% reserve, the same essentials get about 14 h 3 min. The Energy Controller switches to backup with no gap. Which circuits it covers is up to the installer.
The specifications that matter in a power cut
- Usable energy
- 8.76 kWh per unit (also sold as 5.84 kWh)
- Continuous output
- 4 kW
- Peak output
- 6 kW. For 10 seconds, on the larger module.
- Backup
- Whole house, with the gateway (Sigen Energy Controller)
- Solar during a cut
- Yes
- Units per system
- Up to 6
- Chemistry
- LFP (lithium iron phosphate)
- Sold in
- the UK
Source: independent summary of the datasheet, read 2026-09-26.
One, two or three of them
| What it runs | One | Two | Three |
|---|---|---|---|
| Fridge, internet, lights and phones | 3 days 14 h | 7 days 4 h | 10 days 17 h |
| The essentials, with the heating | 2 days 22 h | 5 days 20 h | 8 days 19 h |
| Essentials, heating, cooking and TV | 45 h 17 min | 3 days 19 h | 5 days 16 h |
| The whole house, as normal | 26 h 7 min | 2 days 4 h | 3 days 6 h |
| What it runs | Full | Half full | At a 20% reserve |
|---|---|---|---|
| Fridge, internet, lights and phones | 3 days 14 h | 42 h 53 min | 17 h 9 min |
| The essentials, with the heating | 2 days 22 h | 35 h 7 min | 14 h 3 min |
| Essentials, heating, cooking and TV | 45 h 17 min | 22 h 38 min | 9 h 4 min |
| The whole house, as normal | 26 h 7 min | 13 h 3 min | 5 h 13 min |
What it can run at once
Energy decides how long; output decides what. One Sigenergy SigenStor supplies 4 kW continuously, so the essentials are easy but a big heater, a kettle or a car charger on top can be too much. Motors and compressors also need a start-up surge.
| Add this to the essentials | Everything at once | One SigenStor |
|---|---|---|
| Electric kettle | 3.3 kW | Yes |
| Microwave, 1,000 W output | 1.8 kW | Yes |
| Portable induction hob | 2.1 kW | Yes |
| Space heater, 2,000 W | 2.3 kW | Yes |
| Electric car (3-pin "granny" charger) | 2.6 kW | Yes |
Solar in a power cut
Sigenergy says solar keeps running during a cut.
With 4 kWp of panels (London, 51.5°N), an average day's sun covers the essentials in every month except December. These are averages. A week of thick cloud, common in a British winter, can cut the panels to a fraction of this, so in the darker months plan on the battery alone and count the sun as a bonus.
| Month | Starting full |
|---|---|
| Jan | Keeps going |
| Feb | Keeps going |
| Mar | Keeps going |
| Apr | Keeps going |
| May | Keeps going |
| Jun | Keeps going |
| Jul | Keeps going |
| Aug | Keeps going |
| Sep | Keeps going |
| Oct | Keeps going |
| Nov | Keeps going |
| Dec | 14 days 18 h |
Do solar panels work in a power cut? explains why most systems stop, and what keeps them going.
How full is it when the power goes?
A home battery spends most days charging and discharging to save money, so a power cut finds it at whatever level it happens to be. In the evening in winter that can be close to empty. Most systems let you set a backup reserve that the battery will not use on ordinary days (Tesla calls it Backup Reserve; GivEnergy's app has a similar minimum charge for its emergency supply). The tables here show a full battery, a half-full one, and one sitting at a 20% reserve.
If a storm is forecast, charge it to full. Tesla's Storm Watch does this automatically when a weather warning is issued for your area; on other systems you raise the reserve or force a charge in the app.
No home battery? A power station for the essentials
A portable power station does the same job for the things that plug in, without an installer. The biggest ones hold a third to a half of a home battery. Here is how long each runs the fridge-freezer, the heating, the broadband, the lights and the phones, starting full:
| Power station | Capacity | UK home | US home |
|---|---|---|---|
| Zendure SuperBase V6400 | 6,438 Wh | 40 h 34 min | 19 h 50 min |
| EcoFlow DELTA Pro Ultra | 6,144 Wh | 39 h 47 min | 19 h 43 min |
| Jackery Explorer 5000 Plus | 5,040 Wh | 34 h 48 min | 16 h 41 min |
| Zendure SuperBase V4600 | 4,608 Wh | 31 h 13 min | 15 h 7 min |
| EcoFlow DELTA Pro 3 | 4,096 Wh | 27 h 45 min | 13 h 26 min |
The boiler or furnace is the catch: it is usually wired in, not plugged in, so a power station can only run it through a socket or a changeover switch an electrician fits. The boiler guide and the furnace guide explain how. Each station page has the full numbers and where to buy it.
Amazon links are affiliate searches for a type of product, not endorsements of a model; the site may earn a commission at no extra cost to you. Prices and stock change constantly.
These are estimates from the site's model, not a maker's claim: stored energy × 94% through the inverter ÷ (what the house draws on average + about 30 W for the battery system itself). The sum is explained here.
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