How to calculate a true power?

True power, measured in watts (W), can be calculated using the formula: ( P = VI \cos(\phi) ), where ( P ) is the true power, ( V ) is the voltage in volts, ( I ) is the current in amperes, and ( \phi ) is the phase angle between the voltage and current waveforms. This formula accounts for the power factor (cosine of the phase angle), which indicates the efficiency of power usage in an AC circuit. To find true power, you need to know the voltage, current, and phase angle or the power factor.