To determine the efficiency of an electrical device, you can use the following formula:

Efficiency measures how effectively an electrical device converts input energy into useful output energy. It is expressed as a percentage and is calculated by dividing the output power by the input power and then multiplying by $100\%$. Here, the output power represents the energy produced by the device, while the input power denotes the energy consumed by it.

For instance, consider a device that consumes $100$ watts of power and generates $80$ watts of useful output power. Its efficiency can be calculated as follows:

Substituting the values:

This calculation indicates that the device operates at an efficiency of $80\%$, which reflects positively on its performance. A higher efficiency implies that the device is more capable of converting input energy into useful output energy, leading to cost savings and reduced waste.

It is crucial to recognize that efficiency can vary based on the type of device and the operating conditions. Factors such as temperature, voltage, and load can significantly influence the efficiency of an electrical device. Therefore, analyzing a device’s efficiency under various conditions is essential to obtain an accurate assessment of its performance.