In residential settings, house energy meters typically measure electrical energy consumption in kilowatts (kW) rather than kilovolt-amperes (kVA) because kW represents the actual power consumed by the electrical appliances and devices in the home, whereas kVA represents the apparent power.
Here's why kW is used instead of kVA:
Real Power (kW): Real power, measured in kilowatts (kW), represents the actual power used by electrical devices to perform work, such as providing light, running motors, or heating appliances. It is the power that contributes to useful work and is what you pay for on your electricity bill. In a residential setting, the majority of the load is resistive, such as lighting, heating, and electronics, which primarily consume real power.
Apparent Power (kVA): Apparent power, measured in kilovolt-amperes (kVA), is the combination of real power (kW) and reactive power (kVAR). Reactive power arises due to inductive or capacitive loads (e.g., motors, transformers, fluorescent lights), which do not directly perform work but are necessary for the operation of certain devices. Reactive power does not contribute to useful work and represents power that "bounces" back and forth between the load and the power source.
Power Factor: The power factor is the ratio of real power (kW) to apparent power (kVA) and is expressed as a value between 0 and 1. A power factor of 1 (or 100%) indicates that all the power consumed is being used for useful work, while a power factor less than 1 indicates that some power is being lost as reactive power.
In residential settings, the power factor is generally close to 1 because the majority of the loads are resistive, and there is minimal need for reactive power compensation. Since residential loads primarily consume real power, measuring in kilowatts (kW) simplifies energy monitoring for both the utility company and the consumer. It provides a more accurate representation of actual energy usage and aligns with the way residential electricity bills are calculated based on the real power consumption in kilowatt-hours (kWh).