Which component is essential for measuring the electrical energy consumed over time?

The kilowatt hour meter is essential for measuring the electrical energy consumed over time because it is specifically designed to quantify the total amount of electrical energy used by a circuit or system. This type of meter records energy in kilowatt-hours (kWh), providing a clear and concise measurement that can be easily interpreted by both utilities and consumers.

In contrast, the current transformer is primarily used to measure the current flowing through a conductor, and while it can be a component in some energy monitoring systems, it does not directly provide a measure of energy consumed. Similarly, a volt meter is intended to measure voltage levels in a circuit but does not account for current, and thus cannot determine energy consumption on its own. A phase analyzer is used to assess phase relationships in three-phase systems, which is important for understanding power quality and efficiency but does not measure energy directly.

Therefore, the kilowatt hour meter is the correct choice for this purpose as it integrates both voltage and current to calculate the energy consumed over a specified period.