Fictional worked example

Price a router and idle network accessory

A 10 W router needs to stay connected, but a 5 W accessory on the same power strip may not. Compare the combined load with the router alone.

Inputs and calculation

Router and accessory
Tool input	Value
Currency	USD
Power unit	W
Power	15
Hours per day	24
Days or equivalent sessions	30
Duty cycle (%)	100
Energy price (USD per input kWh)	0.25

15 ÷ 1,000 × 24 × 30 × 100% = 10.8 kWh. 10.8 × 0.25 rounds to USD 2.70.

Tool result · USD 2.70

Router only
Tool input	Value
Currency	USD
Power unit	W
Power	10
Hours per day	24
Days or equivalent sessions	30
Duty cycle (%)	100
Energy price (USD per input kWh)	0.25

10 ÷ 1,000 × 24 × 30 × 100% = 7.2 kWh. 7.2 × 0.25 rounds to USD 1.80.

Tool result · USD 1.80

The removable accessory accounts for 3.6 kWh per 30 days. The router’s own 7.2 kWh remains in the estimate.

Measure idle draw at the wall. Before switching off networking equipment, account for services that need a continuous connection.