Internet during a power outage: how to keep Wi-Fi working

Quick answer

Internet can keep working during a power outage if the equipment that carries the connection through your home stays powered and your provider’s network is still operating. That usually means the modem or fibre ONT, router or gateway, and any switch, mesh node, or access point you actually need.

The important catch is simple: Wi-Fi is not the same thing as internet access. A router can keep broadcasting a perfectly healthy Wi-Fi network while the modem, fibre ONT, neighbourhood cable equipment, or some other upstream part of the connection is dead.

For many homes, backing up the network is still an excellent outage project because the load is small. The trick is backing up the whole required chain, not just the box with antennas.

The connection chain

Wi-Fi is only the last few metres

Every required link has to be working. You control the equipment inside your home. You do not control the provider network upstream.

1. 1

   Provider network

   Central office, headend, outside plant and upstream transport

   Power: Provider-controlled

   →
2. 2

   ONT or modem

   Terminates fibre, cable or DSL at your home

   Power: Your backup plan

   →
3. 3

   Router or gateway

   Routes traffic and usually provides the main Wi-Fi network

   Power: Your backup plan

   →
4. 4

   Switch, mesh or AP

   Extends wired or wireless coverage around the home

   Power: Your backup plan if needed

   →
5. 5

   Phones and computers

   Use the local network and need their own battery or power

   Power: Device battery / backup

Router powered, ONT/modem dead

Your Wi-Fi network may still exist and local devices may still talk to one another, but there is no working path to the internet.

Home network powered, provider path dead

Your LAN can keep working while the fixed internet connection is unavailable upstream.

Home and provider path working

This is the case where battery backup at home can keep the fixed connection online.

Cellular fallback

A second WAN path can help when fixed service fails, but it depends on cellular coverage, capacity and its own backup power.

Start with the boxes in your own house

Before shopping for a UPS or battery, trace the connection from where the provider’s line enters the home to the device making Wi-Fi.

Common layouts include:

If the provider box and router are in different parts of the house, you may need backup power in more than one location.

The fastest way to identify your setup

Follow the provider cable or fibre to the first powered device. If a fibre strand terminates in a small powered box and Ethernet leaves that box for your router, that first box is the ONT. If coax enters a powered box before Ethernet runs to your router, that is typically the cable modem. If the provider line goes straight into one large Wi-Fi gateway, the functions may be combined.

Do not assume the labels on someone else’s setup apply to yours. Canadian providers use different hardware generations and architectures across regions.

Internet backup runtime calculator

The calculator below is deliberately network-specific. It adds up the equipment you need, checks whether an incoming modem/ONT/gateway is actually included, and then estimates battery runtime from information that can support a defensible calculation.

It will not estimate runtime from a UPS VA rating alone. VA describes output capability, not stored battery energy.

1. What needs to stay powered?

These are editable planning placeholders, not universal device specifications. Replace them with your model's measured or documented draw when you can.

Fibre: ONT + routerOne ISP gatewayModem + routerFibre + 2 mesh nodesFibre + PoE network

Fibre ONTincoming serviceWatts

Cable / DSL modemincoming serviceWatts

ISP gateway (modem/ONT + router)incoming serviceWatts

Wi-Fi routerWatts

Mesh node 1Watts

Mesh node 2Watts

Ethernet switchWatts

PoE switch base loadWatts

PoE-powered devices totalWatts

Other network deviceWatts

2. What do you know about the backup source?

Battery / UPS informationI know usable battery WhI know rated battery / power-station WhI have a manufacturer UPS runtime at a known loadI only know the UPS VA rating

Usable battery energy (Wh)

Use this when usable output energy is known or measured.

Planning margin (%)

The lower end of the displayed range subtracts this visible margin for real-world variation.

Your estimate

Selected network load

18 W

Fibre ONT, Wi-Fi router

Incoming internet equipment

Included in this plan

A modem, fibre ONT, or integrated ISP gateway is selected.

Estimated runtime range

8.5 hr to 10 hr

Planning range, not a guarantee. Runtime is usable battery watt-hours divided by the selected continuous network load. The lower end applies your visible planning margin.

Keeping your equipment powered cannot guarantee that your ISP network remains online.

Why VA does not tell you UPS runtime

UPS listings commonly put the VA rating in huge type because it is an important output-capacity specification. It is not a battery-capacity specification.

A UPS might be labelled 600 VA / 330 W. Those figures tell you something about the load the UPS can support. They do not tell you how many watt-hours are stored in its battery or how efficiently the inverter behaves at a 15 W networking load.

For runtime planning, use this evidence hierarchy:

1. Best: a manufacturer runtime curve or table at a load close to your actual network load.
2. Good: known usable battery energy in Wh.
3. Planning estimate: rated battery Wh with explicit efficiency and reserve assumptions.
4. Not enough information: VA alone.

That is why two UPS units with the same VA rating can have different runtimes.

Schneider Electric and CyberPower both separate VA/output ratings from runtime information in their UPS documentation. Manufacturer runtime data is especially valuable for low-power networking loads because battery chemistry, inverter overhead, firmware and battery age can make simple Wh division optimistic.

Fibre internet during a power outage

A passive optical network has an important resilience advantage: the optical distribution path between provider equipment and the home can use passive splitters rather than powered neighbourhood amplifiers. That does not make fibre magically independent of electricity.

At minimum, active equipment exists at the provider side and at the customer side. Your ONT or integrated optical gateway needs local power. Provider-side equipment and upstream transport also need power and must remain operational.

So the practical rule is:

If you have fibre, back up the ONT and router unless your provider has combined them into one powered gateway. Then remember that home backup power still cannot guarantee the provider side of the connection.

A representative Nokia XGS-PON ONT datasheet specifies a 12 V DC supply and less than 8.6 W maximum power consumption. That is useful as proof that some standalone ONTs are genuinely low-draw devices, not as a universal ONT wattage.

Bell publishes outage guidance for keeping current Fibe modem equipment powered with an external backup source. TELUS also makes clear in its Internet Backup material that its connectivity-backup feature does not itself take over during a premises power outage. The exact equipment you need to energize depends on your installation.

Cable internet during a power outage

Cable service has a different upstream dependency. Hybrid fibre-coax networks can include powered neighbourhood equipment outside your house. That means a powered cable modem and router may keep working only while the provider path serving your area remains energized.

This is not a theoretical distinction. Cogeco’s first-party outage guidance explicitly warns that customer equipment on battery can still lose service if a power outage affects the provider distribution node.

That does not mean cable internet always fails the instant neighbourhood power fails. Providers can use their own backup systems, and architectures vary. It means you should not assume that powering your modem guarantees the coax network upstream will remain available for the entire outage.

What about DSL?

DSL still exists in some Canadian areas, but it is no longer the broadband architecture most homeowners should use as the model for outage resilience.

A modern DSL connection needs your modem or gateway powered. It may also depend on powered provider equipment outside the home. Do not confuse this with the historical behaviour of a basic corded telephone powered from the telephone network.

For a current outage plan, treat DSL like any other broadband path: back up your premises equipment, but do not assume the upstream network is immune to a local power failure.

How much power does a router, modem or ONT use?

There is no useful single number for every home network.

Manufacturer energy disclosures show meaningful variation across routers and mesh systems, and equipment with more radios, faster Ethernet interfaces, PoE loads, or heavier traffic can draw more power. A representative standalone ONT can be under 10 W, while a larger integrated gateway or high-end router can be materially higher.

For planning, use this order:

1. Measured wall draw with the equipment operating normally.
2. UPS or smart-plug telemetry if it reports real watts reliably.
3. Manufacturer typical/max power documentation.
4. Power-adapter nameplate as an upper-bound clue, not a claim that the device continuously uses volts × amps.
5. Editable calculator preset only when you have nothing better.

PoE networks need one extra step

If a PoE switch powers access points, cameras or other devices, the switch’s backup load includes more than the switch electronics. It also includes the power delivered to connected PoE devices plus conversion losses.

The easiest approach is to use the switch’s actual total power draw or PoE telemetry during normal operation. If you are estimating from individual devices, include both the switch and the PoE-powered equipment you plan to keep online.

UPS, DC backup or portable power station?

These are three different ways to solve the same small-load problem.

DC backup can be efficient, but compatibility matters more

Many routers, ONTs and modems ultimately run from low-voltage DC. A compatible DC backup can avoid the battery DC → 120 V AC → device DC conversion chain.

But do not improvise the power connection. The replacement source must match the equipment’s required voltage and polarity, provide enough current, and use the correct connector. If the device or provider specifies a particular power supply, follow that guidance.

A power station is not automatically a UPS

Some portable power stations offer pass-through, EPS, backup, or UPS-labelled operating modes. Those terms are not interchangeable across manufacturers.

If uninterrupted operation matters, check the manufacturer’s documented transfer behaviour for the exact model. A brief reboot is usually only annoying for a router, but a modem or ONT may take additional time to re-establish service after power returns.

For a general Wh-based battery calculation, use the portable power station runtime calculator. The calculator on this page is better when you want to model the network dependency chain itself.

You may not need every mesh node during an outage

A useful way to extend runtime is to reduce the network to its essential path.

If your house normally uses a modem or ONT, a main router, and three mesh nodes, ask whether the main router alone provides enough emergency coverage. Every powered node adds load and may require a separate backup source in another room.

During a long outage, it can be smarter to keep:

• the modem or ONT,
• the main router or mesh base,
• one strategically located access point if needed,
• and only the switch or PoE devices that matter.

That is load shedding for the network. Fewer boxes usually means longer battery runtime.

Cellular backup solves a different failure

Battery backup and connection backup are not the same thing.

Battery backup keeps the fixed internet equipment powered.

Connection redundancy gives you another path to the internet when the fixed connection itself fails.

That second path might be a phone hotspot, dedicated cellular modem, dual-WAN router, or a provider-managed cellular fallback service.

Rogers, Bell and TELUS all publish consumer backup-connectivity options, but they work differently:

A phone hotspot is still worth having even if you never buy dedicated failover hardware. Just remember that cellular towers and backhaul can also be damaged, congested, or unavailable during a widespread emergency.

A practical outage setup

A good home-network backup plan is boring in the best possible way:

1. Identify the first powered ISP device and every downstream box required for the coverage you actually need.
2. Measure or document their wattage.
3. Choose a backup source with a runtime method you can defend.
4. If it is a UPS, prefer a manufacturer runtime point near your load over VA-based guesswork.
5. Test the setup by unplugging utility power and confirming the modem/ONT, router and required Wi-Fi coverage stay alive.
6. Re-test periodically because batteries age.
7. Keep a cellular fallback plan for the case where your fixed provider path fails upstream.

Frequently asked questions

Does internet work during a power outage?

It can. Your modem or fibre ONT, router/gateway, and any required networking equipment need backup power, and your provider’s network must still be operating. Home battery backup solves only the equipment you control.

Does Wi-Fi work during a power outage?

Wi-Fi can work if the router or access point stays powered. But a working Wi-Fi signal does not prove that the internet connection is working. Local network traffic may continue even when the WAN connection is down.

Do I need battery backup for both the modem and router?

If they are separate devices, normally yes. A fibre setup may have a separate ONT instead of a modem. Some ISP gateways combine the incoming connection and routing functions in one box.

Is a 600 VA UPS enough for a router and modem?

It may have plenty of output capacity for the load, but 600 VA does not tell you the runtime. Check the UPS’s watt rating and, more importantly, the manufacturer’s runtime curve near your actual network load or the battery energy information.

How many watts does a Wi-Fi router use?

It depends on the exact model, radios, ports and workload. Do not plan a battery system around one universal router wattage. Measure your router or use manufacturer documentation when possible.

Will fibre internet work if I put the ONT and router on a UPS?

It may, and passive fibre distribution can avoid some powered neighbourhood equipment found in other access technologies. But service still depends on provider-side equipment, upstream transport and an intact physical fibre path. A UPS at home cannot guarantee those remain available.

Will a power station keep internet equipment from rebooting?

Only if the exact model’s backup/pass-through transfer behaviour is fast enough for your equipment. Check the power-station documentation rather than assuming every EPS or UPS-labelled mode behaves the same way.

Should I keep every mesh node powered?

Not necessarily. If the main router or one central node provides enough emergency coverage, shutting down distant mesh nodes can reduce load and simplify the backup setup.

Methodology and verification

Methodology

This guide was rebuilt from Canadian ISP support documentation, UPS manufacturer guidance, networking-equipment power documentation, telecom architecture references, and Canadian electrical-product safety guidance. Device wattages in the calculator are editable planning placeholders, not claims that every device in a category uses the same power.

The runtime calculator intentionally uses different methods depending on what the user actually knows. Manufacturer runtime data close to the real load is preferred for UPS units. Known usable Wh can be divided by continuous load. Rated Wh requires explicit efficiency and reserve assumptions. A VA-only UPS entry produces no runtime because apparent-power capacity is not stored energy.

ReadyHome does not assume that a powered home network means the provider network is available. Fibre, cable and DSL sections are written around dependency differences rather than promises about any provider, neighbourhood, or outage.

Related guides

Keep planning

UPS battery backup Canada→Choose a UPS for short outages and electronicsUPS vs power station→Compare the two backup approachesPortable power station runtime calculator→Estimate general Wh-versus-load battery runtimeGenerator size calculator→Add networking gear to a larger household backup planBackup power hub→All ReadyHome backup power guides and tools