How Long Can a UPS Run a Router and Modem?

When the power goes out, your internet usually goes with it. Usually the service itself is still up — it’s your home equipment that’s lost power. (Here’s our full outage checklist.) The good news is that internet gear is one of the easiest things to back up.

Most home internet setups draw only 20 to 40W, about the same as a single light bulb. A basic router-and-modem setup is often around 25W total, which is why even a small UPS (Uninterruptible Power Supply) can keep you online for hours.

Quick Answer

For a typical setup of router + modem at about 25W, here are typical runtimes by battery size:

• 150 Wh: about 4 hours
• 300 Wh: about 8 hours
• 600 Wh: about 16 hours
• 1000 Wh: about 27 hours

The exact answer depends on whether you also need to power any extra equipment, such as a fiber ONT (Optical Network Terminal), a switch, or extra mesh nodes.

Typical Internet Gear Wattage

Setup piece	Typical draw
Wi-Fi router	10 to 20W
Modem	5 to 15W
Small network switch	10 to 25W
Fiber ONT	5 to 10W
Mesh node	8 to 15W each

Home internet gear is a steady load. There is no startup surge to plan around, which makes backup much simpler than for a fridge or microwave.

What This Looks Like in Practice

Setup	Total load	150 Wh	300 Wh	600 Wh	1000 Wh
Router only	15W	~6.5 hrs	~13 hrs	~26 hrs	~43 hrs
Router + modem	25W	~4 hrs	~8 hrs	~16 hrs	~27 hrs
Router + modem + switch	45W	~2.2 hrs	~4.5 hrs	~9 hrs	~15 hrs

Darker cells mean longer runtime. The pattern matters more than the exact number.

These aren’t exact — real runtime shifts with battery age, temperature, and inverter losses — but they’re directionally reliable.

Try It in the Calculator

To get the exact answer for your setup, open the calculator with a scenario close to yours and adjust from there:

Setup	4 hours	8 hours
Router only	Calculate	Calculate
Router + modem	Calculate	Calculate
Router + modem + switch	Calculate	Calculate
Router + fiber ONT	Calculate	Calculate

If you have fiber, the ONT matters too. It only draws about 5 to 10W, but if it is off, your router still has nothing to connect to.

What Size UPS Is Enough?

If you just need to stay online through the outage, you usually do not need a large battery.

• For a 2 to 4 hour outage, almost any decent UPS will do.
• For a 4 to 8 hour outage, look at a mid-size UPS or a small power station.
• For an all-day outage, a power station usually makes more sense than a traditional UPS.

The main advantage of a UPS is instant switchover. Your router stays up instead of rebooting. A power station often gives you more runtime for the money, but some models pause briefly when wall power drops, which can reboot your router and modem. For a full sizing walkthrough, see How to Size a UPS for Your Home Office.

What People Miss

Fiber users need to power the ONT. If the ONT is off, the router cannot do anything useful.

Mesh systems add up faster than people expect. Two or three nodes can double or triple the load compared with a single-router setup.

Cable and fiber are different. Cable usually means modem + router. Fiber usually means ONT + router.

Old UPS batteries fade. Runtime after a few years may be well below the original estimate.

Your ISP can still fail upstream. Keeping your own gear powered does not guarantee the neighborhood network is still live.

UPS vs. Power Station

For a deeper comparison, see UPS vs Portable Power Station: Which Do You Need?

	UPS	Power station
Switchover	Instant, so the network gear usually does not reboot	Some models have a short switchover delay
Runtime	Shorter runtime for the money	Much longer runtime
Best fit	Short outages and clean handoff	Longer outages and better value per watt-hour

For short outages, a UPS is usually fine. For all-day coverage, a power station is usually the better tool.

Bottom Line

A router and modem are a light load. At about 25W combined, even a modest UPS can keep your internet running for several hours.

If you have fiber, include the ONT. If you have mesh, count every node. If you want longer runtime or you want one battery to cover several jobs, a power station is usually the better buy.