Power in an alternating current (AC) circuit can be calculated using the formula:

In an AC circuit, power refers to the rate at which energy is transferred from the source to the load. The total power delivered to the load can be expressed as the product of voltage and current:

However, in AC circuits, the voltage and current are often not in phase with each other. This phase difference means that not all of the power is effectively transferred to the load; some of it is considered reactive power, which is measured in volt-amperes reactive (VAR).

To determine the actual power delivered to the load, we must account for the phase difference between the voltage and current. This is represented by the power factor, which is defined as the cosine of the angle $\theta$ between the voltage and current waveforms. Thus, the effective power delivered to the load can be calculated using the formula:

where $\theta$ is the phase angle.

Improving the power factor can be achieved by adding either a capacitor or an inductor to the circuit. These components help compensate for the reactive power, thereby aligning the voltage and current more closely in phase. This process is known as power factor correction.

In summary, the power in an AC circuit can be calculated using the equation:

where $\theta$ is the phase angle between the voltage and current waveforms. Implementing power factor correction can enhance the power factor and minimize the amount of reactive power in the circuit.