Fictional worked example

One-person home office

A remote worker has measured an 80 W computer and wants to know how much a separate 25 W monitor adds over 22 workdays.

Inputs and calculation

Computer alone
Tool input	Value
Currency	USD
Power unit	W
Power	80
Hours per day	8
Days or equivalent sessions	22
Duty cycle (%)	100
Energy price (USD per input kWh)	0.25

80 ÷ 1,000 × 8 × 22 × 100% = 14.08 kWh. 14.08 × 0.25 rounds to USD 3.52.

Tool result · USD 3.52

Computer and monitor together
Tool input	Value
Currency	USD
Power unit	W
Power	105
Hours per day	8
Days or equivalent sessions	22
Duty cycle (%)	100
Energy price (USD per input kWh)	0.25

105 ÷ 1,000 × 8 × 22 × 100% = 18.48 kWh. 18.48 × 0.25 rounds to USD 4.62.

Tool result · USD 4.62

The monitor adds 4.4 kWh, or 1.10 over the work month. Summing powers is appropriate here because both devices run for the same hours.

Use average power over the work session. Sleep time and weekend use are outside this estimate.