What it draws
Router and Modem
A router and a modem together are one of the cheapest loads in the house and one of the most useful things to keep alive, right up until the point where keeping them alive changes nothing because the provider equipment down the street is also dark.
Typical draw, and the number that actually applies
A modem and a router together usually sit somewhere between 10 and 25 W. Each device has its own power adapter, and the output rating printed on that adapter is the ceiling for that device.
Read the nameplate. It is usually a sticker on the back, inside a door, or on the power adapter, and the figure printed there is a maximum for that specific unit rather than a typical reading. Any range on this page is a starting point for arithmetic, not a substitute for that label.
- Running watts used here
- 15 W
- Duty share applied
- Continuous
- Average draw for the estimate
- 15 W
Hours from a 1024 Wh battery
The row stops at 24 blocks; the estimate runs past it. Estimated hours from the reference battery at 15 W average draw. An estimate, not a guarantee.
The arithmetic, in full
hours = (rated Wh x 0.85) / average watts
average watts = 15 W running x 1, continuous = 15 W
= (1024 x 0.85) / 15 W = 870 Wh / 15 W
The estimate below covers a modem and a router running continuously. Mesh systems with several nodes draw more, roughly in proportion to how many nodes you power.
The derate of 0.85 covers inverter conversion loss and the share of rated capacity a pack will not hand back. It is one planning figure applied to every unit on this site, not a measurement of any particular model.
Starting surge
This load has no meaningful starting surge. It draws essentially the same at switch-on as it does a minute later, which makes it one of the easy ones: if the continuous output is large enough, the load will run.
Duty cycle
This load draws continuously while it is switched on, so no duty share is applied and the average draw is the running draw. Switching it off is the only thing that reduces it.
How to get by without powering it
Every watt-hour you do not spend is one you still have. These are the moves that cost nothing.
- Check whether your service is actually up before spending battery on it. If the neighborhood equipment is unpowered, your router is a space heater with lights on it.
- Use a phone as a hotspot on cellular instead. Cellular sites often stay up on their own backup when residential service does not.
- Power only the modem and the main router. Mesh nodes in rooms nobody is sitting in are a straightforward waste.
Where this sits in the sequence
This load becomes realistic at stage 2, and not before. Read that stage including the part about what it does not cover, because the limits are the useful half.
Related gear
Products live on the gear pages rather than here, because the decision on this page is about arithmetic and the decision there is about hardware.