How long will an Enphase IQ Battery 5P last in a power cut?
A full Enphase IQ Battery 5P (5 kWh usable) runs the fridge-freezer, heating controls, broadband, lights and phones for about 40 h 5 min in a British home, and about 20 h 18 min in an American home with a gas furnace. Running the whole house as normal, it lasts about 14 h 54 min.
Starting at a 20% reserve, the same essentials get about 8 h 1 min. Backup needs the IQ System Controller. Each battery adds 3.2 kW of output, so several together run bigger loads.
The specifications that matter in a power cut
- Usable energy
- 5 kWh per unit
- Continuous output
- 3.2 kW
- Peak output
- 6.4 kW. About 6.4 kVA for 3 seconds (27.82 A at 230 V, from the UK datasheet).
- Backup
- Whole house, with the gateway (IQ System Controller 3)
- Solar during a cut
- Yes
- Units per system
- Not stated on the datasheet
- Chemistry
- LFP (lithium iron phosphate)
- Warranty
- 15 years or 6,000 cycles
- Sold in
- the UK and the US
Source: maker's datasheet, read 2026-09-26. Sunlight Backup: https://enphase.com/homeowners/sunlight-backup-user-guide
One, two or three of them
| What it runs | One | Two | Three |
|---|---|---|---|
| Fridge, internet, lights and phones | 2 days 1 h | 4 days 2 h | 6 days 3 h |
| The essentials, with the heating | 40 h 5 min | 3 days 8 h | 5 days |
| Essentials, heating, cooking and TV | 25 h 51 min | 2 days 4 h | 3 days 6 h |
| The whole house, as normal | 14 h 54 min | 29 h 48 min | 44 h 43 min |
| What it runs | Full | Half full | At a 20% reserve |
|---|---|---|---|
| Fridge, internet, lights and phones | 2 days 1 h | 24 h 29 min | 9 h 47 min |
| The essentials, with the heating | 40 h 5 min | 20 h 2 min | 8 h 1 min |
| Essentials, heating, cooking and TV | 25 h 51 min | 12 h 55 min | 5 h 10 min |
| The whole house, as normal | 14 h 54 min | 7 h 27 min | 2 h 59 min |
What it can run at once
Energy decides how long; output decides what. One Enphase IQ Battery 5P supplies 3.2 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 IQ Battery 5P |
|---|---|---|
| Electric kettle | 3.3 kW | Too much at once |
| 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 |
| Add this to the essentials | Everything at once | One IQ Battery 5P |
|---|---|---|
| Microwave, 1,000 W output | 2.3 kW | Yes |
| Space heater, 1,500 W | 2.3 kW | Yes |
| Window air conditioner, 12,000 BTU | 1.9 kW | Yes |
| Sump pump | 1.6 kW | Yes |
| Well pump (1/2 hp) | 1.8 kW | Yes |
| Electric car (3-pin "granny" charger) | 2.2 kW | Yes |
Solar in a power cut
Enphase's IQ8 microinverters with the System Controller keep producing in a daytime cut (Enphase calls it Sunlight Backup). Older microinverters may not.
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 | 8 days 10 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.
Did this match what you measured?
Nothing is sent anywhere unless analytics is switched on, and no text is collected.