NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

If a lamp draws 100W and runs for 5,000 hours per year, how many kWh of energy does it consume per year?

1. 50

2. 100

3. 500

4. 1000

The correct answer is: 500

To find out how many kilowatt-hours (kWh) of energy a lamp consumes per year, you first need to understand the relationship between watts, kilowatts, and hours. A lamp that draws 100 watts, when expressed in kilowatts, is 0.1 kW (since 1 kW equals 1,000 watts). If this lamp runs for 5,000 hours in a year, the total energy consumption in kilowatt-hours can be calculated by multiplying the power consumption (in kW) by the time (in hours). So, the calculation would be: 0.1 kW * 5,000 hours = 500 kWh. This calculation shows the total energy consumed by the lamp over the course of a year based on its wattage and runtime. Therefore, the correct answer, which states that the lamp consumes 500 kWh of energy in a year, aligns perfectly with this calculation.