Power cuts don’t have to cut your internet. Routers and fibre boxes use very little electricity, so a small battery can keep you online for hours.
What needs backup power?
- Fibre: the fibre box (ONT — the small box where the fibre cable enters) and the Wi-Fi router. Many people back up only the router and wonder why the internet still drops.
- LTE/5G: just the router. Note that cell towers can also lose power during long outages.
- Fixed wireless: the rooftop radio’s power injector and the router.
Most fibre networks keep running during power cuts, as long as your equipment at home has power.
Your options
| Option | How it works | Pros | Cons |
|---|---|---|---|
| Mini DC UPS | A small battery with DC outputs (often 9V and 12V) that plugs straight into the router and ONT. | Efficient, silent, affordable, switches over instantly. | Check it has the right voltages and connectors for both devices. |
| Traditional UPS | A battery box with normal plug points. | Easy to use; can also protect a PC. | Wastes energy converting DC→AC→DC, so runs shorter; may beep. |
| Inverter / home backup system | Powers circuits in your home. | Runs everything for longer. | Expensive; must switch over fast enough to avoid a router reboot. |
| Power bank with DC cable | A USB-C power bank with a “trigger” cable that outputs 9V or 12V. | Portable and cheap if you already own one. | Make sure it supports the correct voltage; may not pass through while charging. |
How long will my battery last?
Most fibre boxes use about 5–10 watts and most routers about 6–15 watts. Check the label on each power adapter: watts = volts × amps (for example, 12V × 1A = 12W maximum; real use is usually lower).
Router backup time calculator
Tip: mini UPS and power bank capacities in mAh are usually quoted at the battery cell voltage (3.6–3.7V), not 12V. If you know the Wh rating, use that — it’s more accurate.
Tips
- Test your setup by switching off the plug point at home before the next power cut.
- Replace batteries every few years — capacity drops with age, especially in hot cupboards.
- Laptops, phones and tablets all run on battery, so with a powered router you can keep working during a power cut.
- After power returns, give the fibre box and router a few minutes to reconnect before assuming there’s a fault.
Not sure what’s wrong?
Our free diagnosis finds the cause and gives you a fix list.