Your numbers
1
Your networking equipment
2
Backup duration and battery characteristics
Battery & storage
Battery size for internet router backup
Check off your networking equipment and set your target duration. Get a battery size for staying connected through an outage.
How it works
Three steps to sizing your internet backup
Step 1
Check off your actual equipment
Fiber connections need the ONT included, cable connections need the modem, and both need the router, much like the setup in the home office backup tool.
Step 2
Set your target duration
Since this load is so small, extending coverage to a full 24 hours costs very little extra.
Step 3
Confirm your provider's infrastructure stays up too
Your own backed-up equipment only helps if the upstream connection is also still working. The critical loads calculator can combine this with other essentials.
Understanding internet router backup sizing
Why this is one of the smallest and most worthwhile loads to back up
A full networking setup, router, modem or ONT, and even a mesh extender, draws well under 100 watts combined, figures consistent with typical device ratings in ENERGY STAR's product database, making internet backup one of the cheapest additions to a critical loads system in terms of battery capacity required. Given how central internet access has become to remote work, communication, and staying informed during an emergency, this small investment often delivers outsized value relative to its cost.
Why your own backup doesn't guarantee your connection stays up
Backing up your home networking equipment keeps your router, modem, and any other gear physically powered and running, but this only produces a working internet connection if your provider's upstream infrastructure, the local fiber node, cable amplifier, or cell tower serving your line, also has power, a dependency addressed in the FCC's backup power rules for communications providers. A widespread outage that also knocks out your provider's local infrastructure will interrupt your connection regardless of how well your own equipment is backed up. Checking with your provider about their own backup power arrangements for local infrastructure is worth doing if reliable connectivity during outages matters to you, alongside the setup covered in the home office backup tool.
What an ONT is and why fiber users need it included
An optical network terminal, or ONT, converts the optical fiber signal into an electrical format your router can use, and is a required piece of equipment for any fiber internet connection. Fiber customers need to include the ONT in their backup load list alongside the router, since without it the connection simply won't function even if every other piece of equipment has power, a combined load the hybrid inverter sizing calculator in our Inverters & Equipment category can help account for alongside larger household circuits.
What to do with this number next
If you're backing up more than just networking gear, the critical loads calculator combines this with other essentials, or the security system backup tool covers a related setup if remote work is the main goal. If you're financing a battery system around this and other essential loads, the quick financing comparison tool in our Financing category gives a fast cost overview.
Questions
Frequently asked
A full setup with router, modem, fiber ONT, and a mesh extender at 55 combined watts needs about 1.6 kWh for a full 24 hours, a very small and affordable load to back up.
Only if your internet provider's upstream infrastructure also has power. Backing up your router and modem keeps your home equipment running, but if the neighborhood fiber node or cable infrastructure loses power too, your connection will still go down regardless of your own battery backup.
An ONT, or optical network terminal, converts fiber optic signal into a format your router can use, and is required for fiber internet connections. If you have fiber internet, the ONT needs backup power alongside the router and modem, or the connection won't work even with everything else powered.
A cellular hotspot or a phone's mobile hotspot feature can serve as a simpler backup for basic connectivity needs during a short outage, without requiring any home battery investment, though it typically offers lower bandwidth than a full home internet connection.