What Is Energy? A Simple Definition Anyone Can Understand

It’s the force behind literally everything we do, from the power that comes out of your wall socket to the beating of our hearts. But it’s such a nebulous concept that many of us still ask, “What is energy, anyway?” It’s a question with both simple and complex answers.

Let’s explore what you need to know about this critical part of our universe.

What Is Energy?

At its most basic, you can think of it as “the ability to do work.” We’re not just talking about motivating yourself to take care of that memo or those chores around the house. Any action that changes the state of something requires energy in some form.

In some ways, you can look at energy as the potential to change. Humans have learned to observe and harness various types of power sources that make much of life possible. 

How Do We Measure Energy?

From a scientific perspective, we measure energy using joules. This is a somewhat complicated measurement related to the amount of work done when a certain amount of force moves a mass a certain distance. At their core, all forms and sources of energy can be expressed in joules. 

In the real world, there are many ways to measure fuel sources. One of the most common is the calorie (also known as a kcal or kilocalorie). This measures what is released when we digest the food we consume.

Another is the kilowatt-hour, which measures how much electricity we use. 

What Is the Difference Between Power and Energy?

To understand energy, we must distinguish it from a similar but distinct concept: power. Remember our definition: “the ability to do work.” This is still true, and it measures the amount of work possible.

Power, by contrast, is the rate at which that energy does that work. 

Can You Create Energy? 

No matter how hard you try, the answer is no. It’s one of the fundamental laws governing how the universe operates, known as the principle of conservation of energy. It states that energy in a closed system (like our universe) can neither be created nor destroyed — just transferred from one state or form to another.

Much of what we think of as traditional power sources (heat, movement, electricity) are simply a result of optimizing and harnessing this transformation. 

How Do You Store Energy?

Depending on the nature of the source, you can store it in a variety of different ways. For example, you can store mechanical energy in the tension of a spring, elastic band, or other physical device or by priming an object to use gravity as its power source.

You can store electricity in batteries, which devices and systems then use. There are also less common ways to store energy. For example, you can use it to compress air or pump water, which can power turbines at a later time. 

Learn more: Energy, Power, and Charge: Why They Matter In Batteries

Potential Versus Kinetic Energy

Kinetic energy is easy to understand. We see it around us all the time. It’s “the energy of motion.” It drives a falling apple or a speeding car.

It falls into three subgroups: vibrational, rotational, and translational. As its name implies, vibrational is created by an object vibrating. Rotational is the energy from an object in motion, which becomes translational if these objects smash into one another. 

Potential energy is a bit more complicated. But a good example is a slingshot or stretched rubber band. When you draw the band back, it holds potential power – the ability to do work. When you release the band, this potential energy becomes kinetic. A similar principle applies when you break chemical bonds between atoms and molecules.

What Are the 6 Different Forms of Energy? 

Answering this isn’t as simple as one definition. It comes in six categories. These relate to how we measure and use it. Let’s take a closer look at each of them.

Thermal Energy

This one is among the easiest to explain, as we’ve all felt it. It is simply heat. The movement of atoms and molecules creates it. The faster these atoms move, the more thermal energy they generate. The warmth of a fire or the heat coming off an electronic device are common examples of this form of power.

Radiant Energy 

Radiant energy travels in waves, like light, x-rays, gamma rays, and more. Our biggest radiant wave producer is the sun. Radio waves and microwaves are also examples of the power of this type of energy. It can do everything from transmitting information to preparing food. 

Mechanical Energy 

This type is stored in objects. This is typically through tension, like a spring or rubber band, or motion, like a speeding car or plane. As objects experience more tension or move faster, they store more energy. Mechanical is one of the easiest varieties to harness using simple machines. 

Electrical Energy

Few forms of energy are more important to our daily lives than electricity. Electrical energy refers to the movement of electrons, the negative particles that are part of atoms. In nature, we see this as lightning. When these electrons pass along a wire in a specific way, it creates electricity we can use to power our devices. 

Chemical Energy

This refers to the chemical bonds between atoms and molecules. We can store it by creating new compounds or molecules and release it by breaking them apart. We can harness this in a variety of ways. For example, when your body breaks down the food you’ve eaten, that releases chemical energy. You can also extract it by burning a piece of wood or coal. 

Nuclear Energy

While electrical energy deals with the electrons at the periphery of the atom, nuclear focuses on the protons at its core. Tremendous amounts of potential lie within the bonds between these protons. When they’re split apart, this energy is released. This can manifest in the orderly generation of power at a nuclear plant or in the destructive maelstrom of an atomic bomb. 

Differences Between Renewable and Non-Renewable Energy Sources

Where you get your fuel matters for a variety of reasons, from the ease of procuring it to the impact it has on you, your neighbors, and the world. Humans have most often harvested non-renewable sources. This includes chopping down trees for fuel and using fossil fuels like coal, oil, and natural gas.

Because there’s only a finite amount of these materials on Earth, and we’re depleting them much faster than they’re being created, we’ll eventually theoretically run out or reach a point where extracting the remaining amount isn’t cost-effective. 

On the flip side of this are renewable sources like the sun, the wind, or the power of a rushing river. Through the use of solar panels, windmills, and hydroelectric dams, we can harness the same kind of energy as with traditional, non-renewable resources. 

These renewable sources theoretically come with limitless potential. The only limit to solar power is the number of panels and the amount of sunny weather. More windmills or more dammed rivers can exponentially increase the amount of energy from the same strong wind or flowing water.

Using renewable resources allows us to plan for the long-term, as they’ll be just as plentiful 100 years from now as they are today. Many renewable sources are also better for the environment, as they lack the carbon output of most non-renewable ones.

Keep Reading: What Are the True Benefits of Renewable Energy?

Why Is Energy Important? 

It’s all around us, doing the work that makes our universe go. Literally, nothing happens or changes without some sort of force behind it. Understanding this and the principles of energy is a critical part of doing everything from constructing buildings to powering your devices.