Your cable modem sits in the background, blinking its status lights, consuming electricity every hour of every day — and most households never think about it. Unlike the router, which gets blamed for slow speeds and occasionally restarted in frustration, the modem is typically invisible. It just sits there. Consuming power. Running up your electricity bill in small but continuous increments that add up to a real annual cost.
Understanding your modem’s wattage, what drives that consumption, and how it compares to your router’s power draw gives you the complete picture of what your home internet setup actually costs to keep running — beyond the monthly plan fee. RingPlanet’s 5G fixed wireless internet eliminates the modem from your home network equipment entirely — the 5G router combines modem and router functions in a single device, reducing both the equipment count and the total power consumption of your internet setup. For a complete overview of all home networking equipment power consumption, see our Router Power Consumption complete guide.
What a Modem Does and Why It Consumes Power
A modem — short for modulator-demodulator — is the device that translates your ISP’s signal into a format your home network can use. For cable internet, the modem connects to the coaxial cable entering your home and converts the cable signal into a standard Ethernet network signal. For DSL, it interfaces with the telephone line. For fiber, the equivalent device is called an ONT — optical network terminal — which converts fiber optic signals to Ethernet.
The modem’s power consumption covers three main functions:
Signal processing: The modem continuously processes the incoming and outgoing data signal — converting between the ISP’s transmission format and the Ethernet standard your router understands. More advanced modems handling higher speeds require more processing power.
Network management: The modem manages the connection to the ISP — maintaining registration, handling authentication, managing connection speed negotiation, and monitoring link quality.
Status monitoring and indicator lights: The modem’s LED status lights — power, downstream, upstream, internet, and Ethernet activity indicators — consume a small but continuous amount of power.
Modem Wattage by Type — Complete Data
DOCSIS 3.0 Cable Modems: 4–10W (Typical 5–7W)
DOCSIS 3.0 is the older cable modem standard — still widely deployed as ISP-provided equipment and purchased by households wanting to avoid modem rental fees. These modems handle speeds up to approximately 1 Gbps theoretical but are limited to 200–300 Mbps in most real-world deployments.
Typical examples and their measured wattage:
- Motorola MB7420 (DOCSIS 3.0, 16×4): approximately 5W
- Netgear CM500 (DOCSIS 3.0, 16×4): approximately 6W
- ARRIS SURFboard SB6183: approximately 5.5W
- TP-Link TC7650 (DOCSIS 3.0): approximately 5W
DOCSIS 3.1 Cable Modems: 6–18W (Typical 8–12W)
DOCSIS 3.1 is the current cable modem standard — required for plans above approximately 400 Mbps and for multi-gigabit cable plans. The higher processing requirements for DOCSIS 3.1’s more advanced signal processing increase power consumption relative to DOCSIS 3.0.
Typical examples and their measured wattage:
- Motorola MB8600 (DOCSIS 3.1): approximately 8W
- ARRIS SURFboard SB8200 (DOCSIS 3.1): approximately 9W
- Netgear CM1000 (DOCSIS 3.1): approximately 8W
- Netgear CM2000 (DOCSIS 3.1, 2.5G): approximately 12W
- ARRIS SURFboard S33 (DOCSIS 3.1, 2.5G): approximately 10W
DSL Modems: 3–10W (Typical 4–7W)
DSL modems interface with telephone lines to deliver ADSL, VDSL, or fiber-to-the-node broadband. These modems are among the lower-power options in the modem category — their simpler signal processing requirements relative to DOCSIS cable modems result in lower consumption.
Typical examples and their measured wattage:
- TP-Link TD-W9970 (VDSL2): approximately 5W
- Netgear DM200 (DSL): approximately 4W
- ARRIS NVG468MQ (AT&T provided DSL gateway): approximately 8W
Fiber ONT (Optical Network Terminal): 4–15W (Typical 6–10W)
The fiber ONT is the modem equivalent for fiber internet connections. It converts the fiber optic signal to Ethernet for the home router. ONTs vary significantly in power consumption based on the fiber technology they support and whether they include battery backup.
Typical examples and their measured wattage:
- Nokia G-010G-Q (fiber ONT): approximately 5W
- Calix 716GE-I ONT: approximately 7W
- Motorola ONT with battery backup: approximately 10–15W (battery backup adds consumption)
- Google Fiber Network Box (combined ONT + router): approximately 9W
4G LTE Fixed Wireless Modems and Routers: 6–20W (Typical 8–15W)
4G LTE fixed wireless devices combine modem and router functions in a single unit — connecting to cellular towers and distributing Wi-Fi throughout the home. The combined function means these devices consume more than a standalone modem but replace both the modem and the router.
Typical consumption:
- Entry-level LTE home router: approximately 8–10W
- Mid-range LTE home router: approximately 10–15W
- Advanced LTE home router with external antenna: approximately 12–18W
5G Fixed Wireless Routers: 10–20W (Typical 12–18W)
5G fixed wireless routers — including those used with RingPlanet’s service — combine 5G modem and Wi-Fi router functions in a single compact device. This consolidation makes them the most power-efficient complete internet solution for households that are switching from a separate modem plus router cable setup.
Typical consumption:
- Compact 5G home router: approximately 12–15W
- Full-featured 5G home router: approximately 15–20W
Modem Wattage Comparison Table
| Modem Type | Min Watts | Typical Watts | Max Watts | Annual Cost ($0.16/kWh) |
| DOCSIS 3.0 cable modem | 4W | 6W | 10W | $8.41 |
| DOCSIS 3.1 cable modem | 6W | 10W | 18W | $14.02 |
| DSL modem | 3W | 5W | 10W | $7.01 |
| Fiber ONT | 4W | 7W | 15W | $9.81 |
| LTE modem/router (combined) | 6W | 12W | 20W | $16.82 |
| 5G modem/router (combined) | 10W | 15W | 20W | $21.02 |
Combined Modem and Router Annual Cost — Cable vs. 5G Fixed Wireless
The key power consumption comparison for households considering switching from cable to 5G fixed wireless is the total equipment cost — not just the modem or router in isolation:
| Setup | Modem | Router | Combined | Annual Cost |
| Cable (DOCSIS 3.0 + budget router) | 6W | 8W | 14W | $19.62 |
| Cable (DOCSIS 3.1 + mid-range router) | 10W | 12W | 22W | $30.83 |
| Cable (DOCSIS 3.1 + Wi-Fi 6 router) | 10W | 16W | 26W | $36.44 |
| Cable (DOCSIS 3.1 + gaming router) | 10W | 30W | 40W | $56.06 |
| 5G fixed wireless (RingPlanet, single unit) | — | 15W | 15W | $21.02 |
The 5G fixed wireless single-unit comparison is the key figure — a RingPlanet 5G router consuming 15W replaces both the cable modem and the home router, making it more power-efficient than any standard mid-range or high-performance cable setup.
The Modem Rental Fee Problem — Power Consumption vs. Financial Cost
Many cable subscribers pay a monthly modem rental fee — typically $10–$15 per month — rather than purchasing their own modem. Over a year, this rental fee ($120–$180 annually) dwarfs the electricity cost of running the modem itself ($8–$17 annually at national average rates).
The financial case for purchasing a compatible modem rather than renting one is clear — a purchased DOCSIS 3.1 modem costs $80–$150 and pays for itself in 6–15 months by eliminating the rental fee. The power consumption of a purchased vs. rented modem is equivalent — the electricity saving is not the driver of the purchase decision, but the rental fee elimination is.
Does Modem Power Consumption Vary During Use?
Modem power consumption is relatively stable — more so than routers — because the modem’s primary function is maintaining the connection to the ISP rather than processing variable amounts of internal network traffic. The modem uses approximately the same amount of power during active 4K streaming as it does during a completely idle period, because its job is to maintain the link to the ISP regardless of how much traffic the home network is generating.
The exception is during intensive downloads or uploads where the modem’s upstream and downstream channels are simultaneously fully loaded — this can increase consumption by 1–3W in DOCSIS 3.1 modems processing simultaneous multi-channel data streams.
How to Measure Your Modem’s Actual Wattage
The same measurement methods that apply to routers apply to modems:
Smart plug with energy monitoring: Connect the modem’s power adapter to a monitoring smart plug. The companion app shows real-time wattage and cumulative daily consumption. Because modem consumption is relatively stable, a 24-hour measurement provides a reliable average.
Kill-A-Watt meter: Plug the modem into the Kill-A-Watt between the wall outlet and the modem’s power adapter. The real-time wattage display shows operational consumption immediately.
Power supply label calculation: Find the modem’s power adapter label — it lists output voltage and maximum current. Multiply these figures for the maximum possible consumption — actual operational consumption is typically 50–70% of this maximum for modems.
Should You Turn Off Your Modem at Night?
Turning off a modem at night saves electricity — a 10W modem off for 8 hours saves approximately $2.80 per year at the national average rate. However, cycling a cable modem on and off repeatedly can occasionally cause the modem to require re-registration with the ISP — a process that takes 1–3 minutes during which internet is unavailable.
For most households, the electricity saving from nightly modem shutdown is modest enough that the re-registration inconvenience outweighs it. Turning off the router at night while leaving the modem on is a more practical approach — the router consumes more power and cycles on and off more cleanly without a multi-minute re-registration process.
5G Fixed Wireless — Eliminating the Modem Entirely
Switching to RingPlanet’s 5G fixed wireless internet eliminates the cable modem from your home network entirely. The 5G fixed wireless router connects directly to cellular towers — performing both the modem function (connecting to the internet backbone) and the router function (distributing Wi-Fi to household devices) in a single device.
This has a direct power consumption benefit: one device doing both jobs typically consumes less total power than two separate devices. A RingPlanet 5G router consuming 15W replaces both a DOCSIS 3.1 modem consuming 10W and a mid-range router consuming 12W — reducing total networking equipment power consumption from 22W to 15W, a 32% reduction.
Beyond the power saving, eliminating the separate modem removes a potential failure point from the home network — a device that can malfunction, require rebooting, and needs firmware updates just like the router. Simplifying the home network to a single device reduces complexity, reduces power consumption, and reduces the number of devices that can fail.
What the U.S. Department of Energy Says About Modem Efficiency
The U.S. Department of Energy’s Energy Star program for small network equipment certifies cable modems and other networking equipment that meet efficiency standards — with DOCSIS 3.1 modems required to meet tighter efficiency thresholds than older DOCSIS 3.0 equipment. The DOE’s program identifies continuous power consumption of always-on networking equipment as a meaningful contributor to household electricity costs and recommends choosing certified equipment where available.
Frequently Asked Questions
How many watts does a cable modem use?
A DOCSIS 3.0 cable modem typically uses 5–7 watts. A DOCSIS 3.1 modem uses 8–12 watts. The higher processing requirements of DOCSIS 3.1’s more advanced signal encoding increase consumption relative to the older standard. For a complete wattage comparison across all modem and router types, see our Router Power Consumption complete guide.
How much does a modem cost to run per year?
A typical DOCSIS 3.1 cable modem consuming 10 watts costs approximately $14 per year at the U.S. national average electricity rate of $0.16/kWh. In California at $0.28/kWh, the same modem costs approximately $24.50 per year. For the complete state-by-state cost table, see our Wi-Fi Router Electricity Cost guide.
Does a modem use electricity when no one is using the internet?
Yes — a modem consumes electricity continuously to maintain its connection to the ISP regardless of whether any household devices are actively using the internet. The consumption is essentially constant around the clock.
Should I buy my own modem or rent one from my ISP?
Buying your own compatible modem is almost always the better financial decision — purchased modems cost $80–$150 and eliminate the $10–$15 monthly rental fee, paying for themselves within 6–15 months. The electricity cost of a purchased vs. rented modem is identical — only the rental fee is eliminated by purchasing.
What is the difference between a modem and a router in terms of power?
A standalone cable modem typically uses 6–12 watts. A standalone Wi-Fi router typically uses 8–18 watts. Together they consume 14–30 watts continuously. A 5G fixed wireless router from RingPlanet combines both functions in a single device consuming 12–18 watts — reducing total networking equipment power consumption while eliminating one device from the home network.
Does turning off the modem at night save meaningful electricity?
A 10W modem shut off for 8 hours saves approximately $2.80 per year at the national average rate — a modest saving. More practically, cycling a cable modem on and off daily can occasionally cause re-registration delays with the ISP. Turning off the router at night while leaving the modem on is generally more practical and saves a similar amount since routers typically consume more power than modems.
What is the most energy-efficient internet setup?
A 5G fixed wireless router that combines modem and router functions in a single device is the most energy-efficient complete internet setup — typically consuming 12–18 watts compared to 22–30 watts for a separate DOCSIS 3.1 modem plus Wi-Fi router. RingPlanet’s 5G fixed wireless service ships with a combined device that achieves this efficiency while delivering consistent peak-hour broadband performance.
Related Guides
- Router Power Consumption — Complete Guide
- How Many Watts Does a Router Use
- Wi-Fi Router Electricity Cost
