CWEA Maintenance Technologist Practice Test

How is the energy consumption of electrical devices commonly measured?

1. Watt-hour

2. Volt-hour

3. Kilowatt-second

4. Ampere-hour

The correct answer is: Watt-hour

The energy consumption of electrical devices is commonly measured in watt-hours. This unit quantifies the amount of energy used over a period of time, specifically representing the total amount of watts (power) consumed multiplied by the number of hours that power is used. This measurement is essential for understanding how much electricity a device uses over time, which directly relates to energy costs. In practical scenarios, a watt-hour indicates how many watts of power a device consumes if it were to run for one hour. For example, if a device uses 100 watts and operates for 2 hours, it would consume 200 watt-hours of energy. The other options do not accurately reflect standard measures of energy consumption. Volt-hour could imply a voltage-time concept but lacks the necessary context of power consumption. Kilowatt-second, while it incorporates kilowatts, is not commonly used since energy is usually discussed over time (thus the "hour" in watt-hour). Ampere-hour measures the electric charge and is also not a direct measure of energy consumption in the context of most household and commercial devices. Thus, watt-hour is established as the correct and conventional way to express energy usage.