Treat it as a continuous load when it is always on
For a stable device, average watts ÷ 1,000 × 24 × 365 gives annual kWh. A meter must be able to resolve low power accurately. DOE guidance notes that measurement resolution matters for small standby loads and recommends time-based measurement when power fluctuates.
Measure the extender after it has completed startup and during a representative period with normal network activity. A rating on the power adapter is not the device’s measured average. Record whether indicator lights, Ethernet devices or USB features are active.
Calculate one extender and then the network total
At a steady 4 W, annual energy is 0.004 × 24 × 365 = 35.04 kWh. Multiplying by $0.18/kWh gives $6.3072, rounded to $6.31. Two equal devices would use 70.08 kWh and cost $12.61.
This does not include the modem or main router. Add their measured annual costs to create a network total, but do not multiply the router figure by the number of extenders. Each device needs its own average. If your electricity rate changes during the year, split the annual kWh across the applicable periods instead of using a false single-price precision.
| Average power | Annual energy | Annual cost at $0.18/kWh | Three devices |
|---|---|---|---|
| 2 W | 17.52 kWh | $3.15 | $9.46 |
| 4 W | 35.04 kWh | $6.31 | $18.92 |
| 8 W | 70.08 kWh | $12.61 | $37.84 |
Evaluate coverage before adding another node
A lower-watt extender that fails to provide usable coverage is not an efficient solution. Check placement, compatible bands, backhaul and the area actually needing service. Compare measured network performance and reliability, not only electricity.
If a mesh system replaces the router-plus-extender arrangement, compare the complete number of nodes and required features. The existing mesh guide covers that system-level boundary.
Remove obsolete loads deliberately
List every network device, its purpose and its outlet. An extender left from an old apartment layout may no longer be needed, while another may be essential for work or safety devices. Test coverage before disconnecting anything important.
Keep firmware updated and follow manufacturer placement and ventilation instructions. The annual cost calculation helps inventory the baseload; it does not justify disabling required connectivity.
Choose your next step
Continue with the question that matches your next decision:
Sources & further reading
Numerical examples are illustrative unless explicitly described as measured. This guide does not claim hands-on product testing. Read the methodology and editorial disclosure.