Energy consumption over long duration: An appliance rated at 350 W runs continuously for 24 days. How many kilowatt-hours (kWh) of energy does it consume?

Introduction / Context:
Household and industrial energy billing uses kilowatt-hours. Converting a device's power rating and runtime to kWh is essential for cost estimation and energy management.

Given Data / Assumptions:

• Power P = 350 W = 0.35 kW.
• Time = 24 days of continuous operation.
• 1 day = 24 h → total hours = 24 * 24 = 576 h.

Concept / Approach:
Energy (kWh) = Power (kW) * Time (h). Use consistent units and multiply precisely. Long durations can lead to large energy totals even for modest power ratings.

Step-by-Step Solution:

Verification / Alternative check:
As watt-hours: 350 W * 576 h = 201,600 Wh. Convert to kWh by dividing by 1,000 → 201.6 kWh. Both methods match exactly.

Why Other Options Are Wrong:

• 20.16 kWh and 2.01 kWh: Off by factors of 10 or 100 due to incorrect hour conversion.
• 8.4 kWh: Corresponds to 0.35 kW for only 24 h, not 24 days.

Common Pitfalls:

• Using days directly in the formula without converting to hours.
• Confusing W with kW, leading to tenfold errors in energy.

Final Answer:
201.6 kWh