The formula, and a one-line shortcut
Annual cost = watts x 8,760 hours / 1,000 x price per kWh. A device that draws 1 W all year uses 8.76 kWh. At EIA's US average residential price of 18.16 cents per kWh for August 2026, that is about $1.59 a year. So the shortcut is to multiply the watts by $1.59. EIA's table was released on 23 October 2026, and it marks 2026 values as preliminary. [1]
The rate matters as much as the hardware. In the same EIA table, August 2026 residential prices ranged from 12.72 cents in Nevada to 47.18 cents in Hawaii, with Maine (32.11 cents) the highest in the contiguous states. One watt for a year costs about $1.11 in Nevada, $2.81 in Maine and $4.13 in Hawaii. These are August figures, so your annual average may differ. [1]
| Rate (Aug 2026, EIA) | Cents per kWh | Cost of 1 W for a year | Cost of 10 W for a year |
|---|---|---|---|
| Nevada (lowest) | 12.72 | $1.11 | $11.14 |
| US average | 18.16 | $1.59 | $15.91 |
| Maine (highest contiguous) | 32.11 | $2.81 | $28.13 |
| Hawaii (highest) | 47.18 | $4.13 | $41.33 |
Where the watt figures come from
Use published consumption, not the adapter rating. GL.iNet's datasheets list the Flint 2 at under 20 W and the Beryl AX at under 8 W. Those are ceilings, and a lightly loaded router may draw less. TP-Link lists the TL-SG105 5-port gigabit switch at 2.3 W maximum. Comcast publishes ready-state power for the modems and gateways it deploys, for example 11.00 W for the Technicolor TC4400 DOCSIS 3.1 modem and 18.00 W for the Vantiva CGM4981COM gateway. Comcast notes that individual units may vary. [2][3][4][5]
We could not find a published wattage for the Comet Pro (GL-RM10) remote KVM on the GL.iNet pages we checked on 30 Oct 2026. The worked example below leaves it out and shows what each extra 5 W costs, so you can add a figure from a plug-in power meter.
| Device | Published figure | What kind of figure | Source |
|---|---|---|---|
| GL.iNet Flint 2 (GL-MT6000) router | Under 20 W | Power consumption (adapter 12V/4A) | [2] |
| GL.iNet Beryl AX (GL-MT3000) router | Under 8 W | Power consumption (USB-C 5V/3A supply) | [3] |
| TP-Link TL-SG105 5-port switch | 2.3 W | Maximum power consumption | [4] |
| Technicolor TC4400 cable modem | 11.00 W | Ready-state power, Comcast table | [5] |
| Vantiva CGM4981COM Xfinity gateway | 18.00 W | Ready-state power, Comcast table | [5] |
| GL.iNet Comet Pro (GL-RM10) KVM | Not found on pages checked | Measure it | - |
Worked example: three home-office setups
Each row adds up the published figures, treating GL.iNet's under-20 W and under-8 W as the full 20 W and 8 W. That makes these upper estimates. Costs are per year of 24/7 running. [1][2][3][4][5]
| Setup | Watts (upper) | kWh per year | Nevada 12.72c | US avg 18.16c | Hawaii 47.18c |
|---|---|---|---|---|---|
| ISP gateway only (CGM4981COM) | 18 | 157.7 | $20.06 | $28.63 | $74.39 |
| Cable modem (TC4400) + Flint 2 | 31 | 271.6 | $34.54 | $49.32 | $128.12 |
| Modem + Flint 2 + two Beryl AX mesh nodes | 47 | 411.7 | $52.37 | $74.77 | $194.25 |
| Modem + Flint 2 + 5-port switch (before the KVM) | 33.3 | 291.7 | $37.11 | $52.97 | $137.63 |
| Each extra 5 W (for example, the KVM once measured) | 5 | 43.8 | $5.57 | $7.95 | $20.66 |
Reading the results
At the US average, the gap between a single ISP gateway and a modem-plus-Flint 2 setup is about $21 a year at the upper estimate. That is small next to an internet bill. Use it to sanity-check claims that a router costs a lot to run, not as a reason to choose one router over another.
Mesh is where the watts add up. GL.iNet's mesh documentation lists both Flint 2 and Beryl AX as supported mesh models. Two Beryl AX nodes add up to 16 W, or about $25 a year at the US average and about $66 in Hawaii. If one wired access point covers the house, it will cost less to run than three mesh units. [6][1]
If you bridge an ISP gateway and add your own router, the gateway keeps drawing power as a modem. Comcast's ready-state figure does not tell you how much bridging saves, so plan on paying for both boxes. [5]
Adapter labels overstate the draw
The adapter rating is the most it can supply, not what the device uses. Flint 2's adapter is rated 12V/4A, which is 48 W, against a published consumption under 20 W. Beryl AX's 5V/3A supply works out to 15 W, against under 8 W. Sizing an electricity estimate, or a UPS, from adapter labels would more than double both numbers. Our UPS guide covers the same mistake from the battery side. [2][3]
If you want a real number rather than a ceiling, a plug-in power meter between the outlet and the adapter will show it. Leave it for a full working day, because Wi-Fi traffic and USB devices change the draw.
Checklist for your own estimate
Five steps, in this order, give you a defensible yearly figure.
- List every always-on box: modem or ONT, router, mesh nodes, switch, KVM, and any USB drive powered by the router.
- For each one, find the published consumption figure, not the adapter label. Measure anything without one. [2][3][4]
- Add up the watts, multiply by 8.76 to get kWh per year, then multiply by your rate from your bill or EIA's state table. [1]
- Remember that ISP equipment you cannot unplug counts too. Comcast's table gives figures for its own devices. [5]
- Repeat for any device you are thinking of adding, using the 5 W row as a guide.
Questions before you decide
Can I use the number on the power adapter to estimate cost?
No, it overstates the draw. GL.iNet rates the Flint 2 adapter at 12V/4A, which is 48 W, but lists the router's power consumption as under 20 W. TP-Link's 5-port switch has a 5 V/0.6 A adapter (3 W) and a 2.3 W maximum consumption. Use the published consumption figure, or measure it.
Which electricity rate should I use?
The one on your own bill. If you do not have it, EIA's Electric Power Monthly gives state averages. In the release of 23 October 2026, the US residential average for August 2026 was 18.16 cents per kWh. Nevada was lowest at 12.72 cents and Hawaii highest at 47.18 cents. EIA marks 2026 values as preliminary.
Does bridging my ISP gateway save electricity?
Bridge mode keeps the gateway powered as a modem, so you still pay for it. Comcast lists ready-state power of 9 W to 29 W for the combined modem-router gateways in its energy table, with no separate bridge-mode figure. Adding your own router then adds its draw on top.
Sources & verification
Product details and prices can change. Check the linked provider before buying.
- U.S. EIA Electric Power Monthly, Table 5.6.A: Average Price of Electricity to Ultimate Customers by End-Use Sector, by State Accessed 30 Oct 2026
- GL.iNet Flint 2 (GL-MT6000) datasheet Accessed 30 Oct 2026
- GL.iNet Beryl AX (GL-MT3000) datasheet Accessed 30 Oct 2026
- TP-Link: TL-SG105 5-Port Gigabit Desktop Switch specifications Accessed 30 Oct 2026
- Xfinity Support: Internet equipment energy usage Accessed 30 Oct 2026
- GL.iNet Router Docs 4: Mesh Accessed 30 Oct 2026
Sources link directly to providers. Product buttons may use separately labeled affiliate links. Read our disclosure.