Keep every link
in your internet powered.
A battery beside your router won’t help the modem in the hall. Map the equipment you need, give each location its own backup, and find the weak link.
can break the connection.Check the whole power path.
Map your required equipment
Include every box your connection depends on.
Use measured operating watts at the wall. The number on a power adapter is usually a maximum, not actual use. An ONT is the box that converts fiber to your home network.
Give each location its own backup
Separate rooms need separate batteries unless the devices share a power source.
Each location represents one independent battery. Never enter the same physical battery in two locations. Product examples use US AC ratings, without expansion batteries.
Choose your outage target
How long do you want this equipment powered?
Adjust the runtime assumptions
These are illustrative modeling assumptions, not measured results or guaranteed limits for any product.
For each location: capacity × delivered-energy fraction ÷ (device watts + idle overhead). The fraction combines conversion losses and unavailable capacity; idle overhead is an additional assumption. Actual behavior varies with battery condition, temperature, settings and load.
Try a battery at one location.
Two sourced examples, not a market ranking. You can also enter a battery you already own above.
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Make the plan match
your home.
The shortest runtime among your required locations limits the whole connection. Batteries in different rooms cannot pool their capacity.
Which devices should I include?
Include the modem or fiber ONT, router, and any switch or mesh node needed for the connection you plan to use. Some gateway boxes combine functions: count each physical device once. Optional access points can be excluded.
Will this keep my internet working?
This checks power for your own equipment only. Your provider’s outside equipment must also remain powered and connected. Confirm your service’s behavior with its documentation; some provider batteries only support telephone service. See Verizon’s outage guidance for one example.
What else should I check before choosing a battery?
Confirm the exact model, voltage, outlets, supported UPS or EPS operation, transfer behavior and low-load shutdown settings in its manual. A modeled runtime is not a compatibility certification. Test your own equipment before relying on it. Do not connect a portable battery to home wiring.
Why use a range instead of one runtime?
Manufacturer battery capacity is not the same as energy reaching your equipment. The two scenarios use different delivered-energy and idle-overhead assumptions. They are not statistical confidence bounds; real runtime can fall outside them. A fresh, fully charged battery is assumed.
Where does my plan go?
The calculator runs in this browser tab. It does not upload your entries, create an account or save the plan after a reload. Print the plan if you want to keep it. Hosting and external manufacturer sites have their own access and privacy policies.