Difference Between Energy and Power

Energy vs Power

Power and energy are two terms often used interchangeably. It is common to see even engineers making the mistake of using the terms power and energy interchangeably. The plight of common people can be easily understood thus. Well, the two terms are very closely related but are not the same and there are differences between the two. These two terms are easily understood using a third term called work. Let us see the relation between the two.

Energy

Energy is the ability to do work. It is a very common word in daily life. It takes energy to do any work. You need energy to move your car. You require energy to heat up your home in winters. It is needed to light up the home in nights. We use sun’s energy to make solar panels. Plants use suns energy to make food. Energy is present in many forms such as mechanical, thermal, electrical and chemical. Of course there are atomic and nuclear energy also which are being harnessed to provide electricity to homes. You can tap any source of energy to perform work. We tap the potential and kinetic energy of water falling from a height to make electricity. In power plants, coal is burnt and its chemical energy is converted into electrical energy.

Energy is indestructible and we can only change its form. We use chemical energy from a battery to provide current. To generate steam we burn coal and other fossil fuels, thus converting its stored chemical energy into thermal energy. To heat our homes or to keep interiors cool, we need to convert electrical energy into thermal energy. The smallest unit of energy is Joule but it is insignificant in everyday use which is why we use terms like watt hour or kilowatt hour.

Power

It is a concept that measures how fast energy is being used. So energy is what you deliver and power is the rate at which you deliver it. Let us understand it with an example. You are being supplied energy in the form of electricity. The power rating of different appliances tells you how fast they consume this energy. A 100 watt bulb will of course use energy at a faster rate than a fluorescent bulb that has a power rating of 10 watts. Thus power is the rate at which energy is being used. So the unit of power is joules per second.

Talking of differences, energy is present in many forms and it can be stored whereas power cannot be stored. Power only tells how fast energy is being consumed. In different cars, energy being used remains the same but their engine sizes determine the rate at which energy is being used. This is why smaller cars have better fuel efficiency than larger cars.