Keep Internet Equipment Powered: UPS Setup and Runtime

Start with an uninterruptible power supply (UPS) that powers every home device needed for internet access—not just the Wi-Fi router. Include the modem or fiber terminal, plus any switch or access point needed to reach your devices. Choose the battery by runtime at that combined load, not by the largest watt rating on the box.

A battery can keep your equipment running; it cannot repair an outage in your provider’s network. Comcast notes that a power outage can also interrupt its network. If your equipment stays on but internet access fails, check the provider’s outage status using cellular data, if available, rather than assuming you need a bigger battery.

Identify every device that needs power

Trace the connection from the cable or fiber entering your home to the device you use:

Your setup	Equipment to put on backup power
Cable or DSL with separate boxes	Modem and router
Combined modem/router gateway	Gateway
Fiber with a separate optical network terminal (ONT)	ONT’s power supply and router/gateway
Fiber terminating directly in a gateway	Gateway; confirm whether an external ONT also exists
Network using a separate switch or Wi-Fi access point	The equipment above, plus any switch, access point or power-over-Ethernet (PoE) source required for your connection

A separate fiber terminal is easy to overlook because it may be in a garage or on another wall. AT&T explicitly requires separate backup power for an external ONT. If it is too far from the router for one practical installation, plan backup power at both locations.

Do not assume the provider’s existing battery backs up internet service. As of October 6, 2026, Verizon says its Fios PowerReserve supports voice calls, not Fios Internet or TV. Check the exact equipment and service rather than relying on a “24-hour backup” label.

Choose the right kind of battery backup

An AC UPS is the straightforward starting point. Keep the devices’ original power adapters and connect them to the UPS outlets labeled battery backup. Surge-only outlets do not provide battery power. For example, the CyberPower ST425 has four battery-backed outlets and four surge-only outlets. Count usable outlets with the bulky adapters plugged in, not just sockets on the specification sheet.

A DC mini-UPS can suit compatible networking equipment, but it replaces the original adapter’s DC output. Match the equipment’s required voltage, connector size and polarity, and ensure the UPS can supply at least the required current. A plug that fits is not enough. The Eaton 3S Mini manual for its ANZ model illustrates the need to select the correct voltage and barrel adapter before connecting equipment. Use a provider-approved solution where required, especially for an ONT: AT&T warns that the wrong backup can damage it.

A portable power station is worth considering when you need more stored energy, but verify automatic switchover and continuous-output settings. Charging while supplying power does not, by itself, establish uninterrupted operation. The EcoFlow RIVER 3 manual lists different transfer times for different versions and warns users to check device requirements. It also describes an AC-output timeout. Check your exact model and test whether your networking equipment restarts during transfer.

For the broader differences, see battery backup options for a home outage.

Size for hours, not just watts

Measure each required device’s AC draw during normal use with a plug-in power meter, then add the readings. Central Wisconsin Electric Cooperative explains how these meters measure wall consumption. Do not treat an adapter’s output rating as measured wall consumption.

Two separate checks matter:

• Output capacity: The load must stay within both the UPS’s watt and VA limits. Leave headroom according to its manual. Eaton’s sizing guide distinguishes output capacity from runtime.
• Battery runtime: Find the exact model’s manufacturer runtime curve at your measured load. A 1,500 VA rating is not a battery-energy rating and cannot tell you how many hours the router will run.

For an energy-based comparison:

Energy delivered to equipment (Wh) = combined load (W) × required hours

These are calculated examples, not typical router wattages:

Measured combined load	Energy delivered for 4 hours	Energy delivered for 8 hours
20 W	80 Wh	160 Wh
30 W	120 Wh	240 Wh
50 W	200 Wh	400 Wh

These figures exclude the backup unit’s own consumption and conversion losses. A battery labeled 240 Wh does not necessarily deliver 240 Wh through its AC outlets. Use the manufacturer’s load-specific runtime estimate and verify your setup with a test. Allow reserve rather than planning to reach empty exactly when you need to finish.

Runtime curves are estimates, not guarantees. CyberPower says its curves assume fully charged, new batteries and vary with battery age, charge and operating conditions.

Test the connection before an outage

1. Charge the backup fully and follow its installation instructions, including grounding, ventilation and permitted connections.
2. Put every required network device on battery-backed outputs. Leave unrelated desktop computers and other loads off this battery unless you have included them in the sizing.
3. Follow the model’s battery-test procedure. With cellular data disabled on your test phone, load a fresh webpage to confirm actual internet access—not merely a visible Wi-Fi network.
4. Check for reboots during switchover. If the manufacturer permits an extended runtime test, test through your intended operating period, monitor the battery and stop at the low-battery warning. Recharge afterward. Record the load and result; repeat after equipment or battery changes.

If internet access matters during a provider outage, arrange a separate connection such as a phone hotspot or cellular-backup service and test it beforehand. That is connection backup, distinct from power backup. As of October 6, 2026, Xfinity’s Pro description, for example, describes LTE failover separately from its optional battery. Cellular backup still depends on usable coverage and an operating network.