Do you need a UPS for your modem? How to keep internet on in a power outage
Most home internet outages aren't the provider's fault. The power flickers, the modem reboots, and you lose five minutes or the rest of the day. A small battery backup fixes most of that.
If you work from home, rely on internet calling, or have cameras or alarms on WiFi, yes. A modem and router together typically draw only about 10–30 watts, so an inexpensive UPS can keep them online for an hour or more, and through every short flicker. It won't help if your provider's own equipment down the street loses power too.
Why a power cut takes your internet down
Your modem (or fiber ONT) and router need power. Even a one-second flicker makes them reboot, which can take several minutes. In a longer outage the provider's network often keeps running on its own backup power for a while, so a battery at your end can keep you online when the lights are off.
How long a UPS lasts
Check the watts on your modem, router and any fiber ONT; most draw roughly 10–30 watts combined. A small consumer UPS sized for computers is far bigger than that load, so runtime is often an hour or more, and a larger unit or portable power station can run them for several hours. Runtime charts on the UPS box are listed by watts; find your total load and read across.
Provider battery options
- Xfinity: a battery backup for its Pro WiFi Extender, about $60 one-time, rated for about 4 hours.
- Spectrum Invincible WiFi ($30/mo): 5G backup plus an 8-hour battery.
- Google Fiber: battery backup for $10/mo on Home 3 Gig, included on 8 Gig.
- Fiber providers have long offered battery units for phone service; ask whether yours powers internet too.
What to buy
- A line-interactive UPS with enough outlets for the modem, router, ONT and backup gateway.
- Or a small portable power station if you want many hours of runtime and can also use it for other devices.
- Plug only the network gear into the battery outlets; a TV or computer will drain it fast.
- Replace UPS batteries every few years; most units warn you when they weaken.
When a UPS isn't enough
If the outage takes down your provider's equipment in the neighborhood, your internet goes out no matter what you plug in. For that, you need a second connection on a different network; see the best backup internet, backup internet for remote workers and is your internet down?.
For longer outages and storm prep, see internet during power outages and hurricanes.
- Xfinity, Spectrum and Google Fiber backup and battery pages, as compiled in our backup internet guide, Oct 2026
- Device power ratings are typical ranges; check your equipment labels
Prices and terms change often; confirm with the provider before you order. How we research
A small UPS covers short cuts. A portable power station runs them for hours.
Questions
Will a UPS keep my internet on during a power outage?
It keeps your modem and router powered. Whether you stay online depends on your provider's network having power too; many neighborhood nodes have their own backup for a while.
How long will a UPS run a modem and router?
Most modems and routers draw about 10–30 watts combined, so a small UPS often lasts an hour or more. Check the UPS runtime chart against your total wattage.
What size UPS do I need for a modem?
A small consumer UPS is enough for a modem, router and ONT. Buy for the number of outlets you need and the runtime you want, not the wattage, which will be low.
Do fiber modems need a battery backup?
The fiber ONT and your router both need power. Some fiber providers sell battery units, but many only power phone service; a UPS covers both.