Appliance Database
Wi-Fi is not one device. It is a chain of powered equipment, and every link has to stay on. Use the sizer to add up the gear that actually creates your connection — then pick the runtime you need to survive.
Assumes 90% system/inverter efficiency and a 20% Zaron Energy sizing margin. These are planning assumptions — not universal physical constants. Networking gear has no compressor-style startup surge; size for continuous watts.
Opens the full-home Zaron Energy Backup Power Calculator.
Continuous watts
15–40 W
Typical draw of a modem or ONT plus Wi-Fi router running 24/7. No big spikes, no motor — the load is steady.
Runtime options
6–72 hr
From an overnight outage to a three-day event. Energy is watts × hours — the longer the runtime, the more battery you need.
Chain links
3–4
ISP service, modem/ONT, router/gateway, your devices. Backup power only covers the links inside your home.
The honest answer
“How many watts does Wi-Fi use?” is the wrong question. The right question is: which pieces of your internet chain must stay powered — and how much does each one actually draw?
A fiber home might have an ONT and a router. A cable home might have a gateway doing both. Each adds its own 5–20 W to the total.
Every mesh satellite or extra access point is another always-on radio. Two or three nodes can double a modest network's draw.
Power adapters are rated for their maximum output. Real-world draw is often lower — a plug-in power meter is the only way to know your true number.
The dependency chain
Your battery can keep every device in your house glowing green. If the outage reaches your provider's network upstream, the internet still stops. Backup power covers your side of the wire — nothing more.
That distinction matters for how you plan: keeping your modem and router on a battery protects your local network — cameras, NAS, smart home hub — even when the wider internet is down. It also means your connection may return within seconds when the ISP side recovers.
ISP Service
Your provider's network — outside your control
Modem / ONT
Converts the line into an Ethernet signal · 5–15 W
Router / Gateway
Moves traffic and broadcasts Wi-Fi · 5–20 W
Your Devices
Phones, laptops, cameras, smart home gear
Find your real number
The most accurate sizer result comes from your own gear. Spend five minutes collecting the real figures, then plug them into the sizer above as custom watts.
Check the wall wart: output volts × amps gives a rated maximum. Useful as an upper bound — not a measured draw.
Data sheets and spec pages often list typical or average consumption, which is closer to reality than adapter ratings.
Some modems, ONTs, and gateways print electrical ratings on the underside sticker. Photograph it for reference.
An inexpensive plug-in power meter between the outlet and the device shows true continuous watts. The gold standard for sizing.
TIP: If a device runs on a 12 V DC adapter, it may run directly from a 12 V battery bank with the right plug — skipping inverter losses entirely.
Watts vs. volts vs. hours
Confusing these units is the single most common sizing mistake. Here is the field guide.
| Unit | What it measures | How it fits your backup plan |
|---|---|---|
| Watts (W) | Power — how hard the device works right now | The number you sum across your equipment. Networking gear draws watts continuously, day and night. |
| Volts (V) | Electrical “pressure” from the adapter or battery | Common adapter outputs are 12 V or 5 V DC. Voltage must match your power source — watts must be covered by it. |
| Amps (A) | Current — how much electricity flows | Adapters list a maximum amps rating. The device rarely pulls the full amount for long. |
| Watt-hours (Wh) | Energy — watts sustained over time | A 20 W network running 24 hours consumes 480 Wh. This is what your battery must store. |
| Kilowatt-hours (kWh) | Energy at grid scale — 1,000 watt-hours | Battery capacity is sold in kWh. Portable stations commonly range from 0.25 to 2+ kWh. |
Scenario map
Where the failure happens determines what backup power can — and cannot — fix.
| Scenario | What happens | Does battery backup help? |
|---|---|---|
| Your home loses power | Modem, router, and everything else go dark — unless on a battery. | YES — full protection with a sized battery or UPS |
| Only the router is unplugged | Wi-Fi disappears, but wired devices may still reach the internet. | YES — battery on the router restores Wi-Fi |
| ISP node loses power upstream | Provider's street cabinet or headend goes down; no signal reaches your modem. | NO — nothing inside your home can fix it |
| Regional fiber/cable cut | Physical damage interrupts the line itself. | NO — battery keeps gear on, but there's no signal |
| Extended multi-day outage | Home gear is fine, but batteries drain without recharging. | PARTLY — solar or a generator extends runtime |
Beyond the kilowatt-hour
Unlike a refrigerator, networking gear has no compressor — no surge of watts at startup, no duty cycle. Its draw is boringly flat. That makes it the easiest load in your home to size, but there are still three questions to answer.
Energy is watts × hours. A 20 W network needs 480 Wh for a day — around 0.64 kWh of battery after efficiency and margin. Three days needs triple that.
Modem, router, mesh nodes, and switches all draw simultaneously and continuously. Your inverter or power station must cover the combined watts — with a small cushion, not a huge surge allowance.
No motor surge here — but gear reboots in sequence after an outage: modem/ONT first, then router, then mesh. Budget a few minutes of reconnection time, and watch PoE switches, which power access points over the same Ethernet cable.
A typical always-on home network chain involves three to five powered devices: a modem or ONT, a router or gateway, and often mesh nodes or a switch. Each one is small — but together they define your true continuous load. Count them all.
Real-world variables
The sizer uses representative planning values. Your actual number depends on the specifics of your setup.
A combined modem/router draws once (often 10–20 W). Separate units draw twice — but let you reboot or replace one link at a time.
Fiber installs add an optical network terminal, typically 3–10 W, often in a garage or closet. Easy to forget — always powered.
Every additional satellite adds 4–10 W. Whole-home mesh with three nodes can double the load of a single router.
A simple unmanaged switch sips 4–10 W. A PoE switch powering access points or cameras can draw 50 W or more — size it separately.
Some ISP gear downclocks radios or enters low-power modes at night. Draw varies slightly with firmware and traffic — usually by only a watt or two.
Mesh backhaul units, smart home hubs, and LTE failover dongles often run on USB adapters at 2.5–5 W each. Small, but they add up over 72 hours.
Methodology
Every step of the sizer's math is visible. Audit it line by line — or plug in your own measured watts and rerun it.
Total continuous watts
Sum of every networked device you selected, plus any custom watts. This is the load your power source must sustain.
— W
Watts × runtime hours
Continuous load multiplied by the runtime you chose (6, 12, 24, 48, or 72 hours). Result is energy in watt-hours.
— Wh
Convert Wh → kWh
Divide watt-hours by 1,000 to express energy in kilowatt-hours — the unit batteries are sold in.
— kWh
Account for system efficiency
Divide by 0.90 for assumed inverter/conversion losses between the battery and your devices.
÷ 0.90
Apply Zaron sizing margin
Multiply by 1.20 — a Zaron Energy planning margin for battery aging, temperature, and real-world slack.
× 1.20
Recommended battery capacity
Energy ÷ 0.90 × 1.20. Sized so the load runs your full runtime with headroom to spare.
— kWh
Assumed 90% efficiency and the 20% margin are Zaron Energy planning conventions — sensible defaults, not physical constants. Battery datasheets, inverter specs, and your own measurements always override them.
Evidence
Every figure on this page traces to one of four categories — and we label which is which.
Power adapters, underside labels, and published datasheets define each device's rated volts, amps, and maximum watts.
Representative ranges for routers (5–20 W), modems (6–15 W), and ONTs (3–10 W) reflect commonly published measurements and plug-meter studies across consumer networking gear.
Wh = W × h; kWh = Wh ÷ 1,000; recommendation = kWh ÷ 0.90 × 1.20. Fully transparent and reproducible above.
The single biggest accuracy lever. Enter your own measured or labeled watts as custom input and the sizer adapts instantly.
Zaron Energy did not physically test the equipment discussed on this page. Representative wattages are planning defaults drawn from published documentation and commonly reported measurements — always verify against your own device labels or a plug-in power meter. Nothing here is a lab report; it is a sizing framework.
Straight answers
Most home Wi-Fi routers draw between 5 and 20 watts continuously, with many everyday models averaging around 6–10 W. High-performance routers with multiple radios run hotter. The number on the power adapter is a maximum rating, not a measured figure — the router usually draws less in real use.
Divide the battery's usable watt-hours by the router's continuous watts. A 10 W router on a 300 Wh battery runs roughly 30 hours before losses; with a 90% system efficiency assumption and a 20% sizing margin, plan on about 24 hours. For a full chain — modem plus router — use the sizer at the top of this page.
Only if two things stay powered: your home equipment (modem or ONT, router or gateway) and your internet provider's network upstream. Battery backup keeps your local gear running — it cannot keep an ISP's street cabinets or headends online if the provider loses power. Your local network (cameras, NAS, file shares) keeps working either way.
Not a meaningful one. Unlike refrigerators or pumps, networking gear has no motor or compressor. Power draw stays near its continuous level at startup, so you size the inverter for continuous watts — though keeping a modest cushion is still good practice. After an outage, expect a few minutes of reboot and reconnection time as equipment comes back in sequence.
Count it once. A combined modem/router gateway typically draws 10–20 W — comparable to separate units, not double. Check the gateway's power adapter or spec sheet for its rating, or measure it with a plug-in power meter for the true figure.
Multiply volts by amps: watts = volts × amps. A 12 V, 1.5 A adapter is rated for up to 18 W. Treat that as the ceiling — the device's real draw is usually lower. For a true number, use an inexpensive plug-in power meter and enter the measured watts as a custom input in the sizer.
A UPS is designed to bridge seconds to minutes so computers can shut down safely; many small units only cover 10–30 minutes under load. For outages lasting hours, size a battery in kilowatt-hours: your equipment's continuous watts multiplied by the runtime you need, adjusted for efficiency and margin — exactly what the sizer above calculates.
Appliance database
Internet is one essential load. Add the rest of your home to build a complete outage plan.
The whole-home view
This page sizes your internet and networking load. The full Zaron Energy Backup Power Calculator combines it with your refrigerator, freezer, lighting and every other essential load — into one number you can act on.
Open the Full-Home Calculator