Difference Between Power and Energy

Energy and power are two terms that people often use interchangeably in daily life. However, when dealing with Physics, both of these differ in definition, scope and many other factors. Thus, understanding the difference between power and energy is crucial. 

However, before proceeding to a detailed power vs energy comparison, let us learn a bit more about these two terms.


What is Power?

Power is a scale that measures the speed for completing work. Therefore, power is how quickly one can complete work. In essence, it refers to the consumption of energy per unit time. 

Any object that transfers higher energy in a limited time can be termed to possess greater power. The SI unit of energy is Watts, which is Joules/second. 


Example of Differing Power

Suppose that A, B and C set out on jogs of 5 km. A completes the jog in 20 minutes, while B and C take 23 minutes and 25 minutes, respectively. In this case, each participant completes the same amount of work. 

However, A expends the greatest amount of power. C, on the other hand, uses the least amount of power amongst the three.


What is Energy?

Energy refers to an object or an individual’s ability to do work. The amount of time that one can work defines their energy. Therefore, like power, time is a crucial factor when determining energy. In scientific terms, energy is transferred from one object to another. The SI unit of energy is Joules, which can also be expressed as watt-hour. 

Energy can be Divided into Several Types, Such as – 

  • Heat

  • Potential

  • Kinetic

  • Electric

  • Mechanical

  • Nuclear

  • Light

Before venturing into the difference between power and energy, you should also know that there are only two sources of energy – renewable and non-renewable. Coal and petroleum are non-renewable sources, while wind and water are renewable energy sources.


Example of Energy

For instance, consider a bowler in a bowling alley. The bowling ball rolls toward the standing pins, and transfers its energy into the pins that it hits, thereby sending them flying. The bowling ball, on the other hand, acquires its energy when the bowler throws it on the lane.


To understand the difference between power and energy in physics, consult the table below. 


What is the Difference Between Energy and Power?

Comparison Basis

Energy 

Power

Definition

Energy is an object’s ability to complete work.

Power refers to the rate at which an object can complete work.

SI Unit

Energy’s SI Unit is Joules.

SI Unit for power is Watt. 

What it represents

How much work an object or individual can complete.

How fast an object or individual can complete the work.

Applications

Energy is required for all kinds of work, including walking, running, care movement and more.

Power is common in mechanical, heat and electrical applications. 

Symbol

Energy is denoted by W.

P is used to denote power.

Conversion

You can convert energy from one form to another. 

Power cannot be converted.

Storage

One can easily store energy.

Storing power is impossible.


Now you know the difference between power and energy. Take a look at the common formulas for calculating energy and power.


Calculating Power

  • General calculations - Power (P) = Work/time

  • Standard electric power formula – Power = Voltage/Current

  • Electric power in resistors = I2R, where I is the current and R is the resistance.


Calculating Energy

  • Kinetic energy – K.E = \[\frac{1}{2}\] mv2, where m is the object mass, and v is its velocity.

  • Potential energy – P.E = mgh, where m is mass, g is the gravitational acceleration and h refers to object height.

  • Electric energy – W = P x t, where P is power and t is time.

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FAQ (Frequently Asked Questions)

1. What is the Difference Between Electric Energy and Electric Power?

Ans. Electric energy is generated from potential difference in a circuit, causing current to flow. Electric power is the rate at which electric energy is transferred within a circuit.

2. What is the SI Unit of Power?

Ans. The SI unit of power is Watt, which can be defined as Joule/second.

3. How can Power be Stored?

Ans. Power cannot be stored for usage later. You can only store energy.