How do you keep the internet on during a power outage?
Scenarios Updated 2026-08-08
Plug the router and the modem into a power station and nothing else. A cable-modem gateway on the European Commission’s own configuration table draws 9.1 W, all 12 published US machines in this library carry the pair without qualification, and the smallest machine that states enough about itself to be divided holds them for 14 h against 83 h from the largest.
The number to distrust is the one printed on the power adapter. A common 12 V 3.5 A brick is marked 42 W, roughly four times what the equipment behind it actually uses, and sizing a battery from it is the most expensive mistake available on this particular load.
Where these figures come from, and why that changes how to read them
We found no published equipment-consumption figure from any brand that sells this hardware; what is on the box is the power supply’s rating. So the usable figures in this record come from somewhere else entirely: a European Commission voluntary code of conduct for broadband equipment, a US ENERGY STAR specification that has since been retired, and an EU ecodesign regulation that sets a legal maximum rather than reporting a measurement. That provenance is unusual enough to be worth stating on the page, because it changes how the numbers should be read — a regulatory allowance is an upper bound that compliant equipment sits under, not an average of what is on shelves.
What a home network costs to keep alive
Four figures, three of them from regulators and standards programmes rather than from a brand, and one of them arithmetic of ours with its terms written out.
A DOCSIS 3.0 customer-premises device with one gigabit port, as a worked configuration example in the EU broadband code of conduct.
See the record →The base allowance for a router in the ENERGY STAR small-network-equipment specification. The programme has been retired; the allowance table is still the only structured US reference of its kind.
Two boxes rather than one, at the top of the range the same code of conduct’s examples describe. This is the figure worth sizing against if you do not know what is on your wall.
An EU ecodesign ceiling for high-network-availability equipment, not a measured draw — and the reason a router has no useful standby state at all. It is designed to answer the network at any moment, so our engine treats it as running all day.
The figure the record carries, and the one this article goes on to argue with.
17 W from the record's own upper bound, times 24 hours. The upper bound is the record's; the multiplication is ours.
See the record →Official spec + Derived by WattPairverified 2026-08-01router + modem record · EU JRC, ENERGY STAR, EU ecodesign
The connection sets the number, not the brand
The same code of conduct’s configuration examples run from a plain Ethernet router at 3.2 W through an ADSL gateway at 5.5 W to a VDSL2 triple-play gateway at 9.3 W, beside the cable device’s 9.1 W. The retired ENERGY STAR table adds the same way: 0.3 W per gigabit port, and 1.3 W for each spatial stream a Wi-Fi radio can receive. So "how many watts does a router use" has an answer shaped like a configuration rather than a product, and the answer for your house is set by how the internet gets into it.
The pair against the published US library, computed on this build
Read the load-ratio column and then stop reading. The largest machine here sits at a fraction of one per cent of continuous output and the smallest at three per cent; nothing about this load separates one machine from another, which is why there is no ranked list of them.
The smallest published machine in the library, and the load still barely registers on it.
Show the working →14 h — a full night and most of the next day from a machine you can carry in one hand.
Show the working →83 h. Three and a half days of network, if nothing else is plugged in.
Show the working →Our own record is optimistic, and our own engine says so
This record carries a derived helper figure of 408 Wh for a day online, and a note beside it saying a 500 Wh machine therefore keeps a house connected for about twenty-four hours. That division left the inverter out. Our engine does not: it divides usable capacity by the load plus the machine’s own self-consumption, which on the record that states one is 10 W. A day at the headline draw is 458.4 Wh delivered on that basis, and a day at the record’s own upper bound is 648 Wh — comfortably past the 500 Wh the note describes as enough. The note is right for a mid-range gateway and wrong at the top of the band it was computed from. We are stating that here rather than deleting it, because a corrected page and an uncorrected record is a worse outcome than both of them saying the same thing out loud.