Learn what energy density means and how natural gas compares to other fuels. A clear, student-friendly guide with examples and calculations.
Not all fuels are equal. Some give you a lot of energy from a small amount. Others need a lot of material to give you the same energy. This is called energy density. It is one of the most important properties of any fuel.
Energy density tells you how much energy is stored in a given amount of fuel. Fuels with high energy density are great for things like cars and airplanes. You can store lots of energy in a small tank. Fuels with lower energy density work better for things like home heating, where space is not a problem.
Natural gas has an interesting energy density story. By weight, it is excellent. By volume, it is not so great. That is why we compress it or liquefy it for transport. Understanding energy density helps explain why we use different fuels for different jobs.
Energy density is the amount of energy stored per unit of fuel. Scientists measure it in two ways. Energy per unit mass is measured in megajoules per kilogram (MJ/kg). This tells you how much energy you get from a certain weight of fuel. Energy per unit volume is measured in megajoules per liter (MJ/L). This tells you how much energy you get from a certain volume of fuel.
The two measurements can give very different results. A fuel might have high energy by weight but low energy by volume. Natural gas is a good example. It is light, so a kilogram contains lots of energy. But it is a gas, so a cubic meter does not contain much energy compared to liquid fuels.
Energy density is different from specific gravity. Specific gravity compares the weight of a fuel to the weight of an equal volume of water. It tells you how dense a material is, not how much energy it stores. Energy density is about energy, not weight.
At standard temperature and pressure, natural gas has a density of about 0.000717 kg per liter. That is very light. For comparison, water is about 1 kg per liter. Gasoline is about 0.74 kg per liter.
The energy density of natural gas by mass is about 50 MJ per kg. That is excellent. Here is how it compares to other fuels by weight:
By weight, natural gas beats almost every common fuel except hydrogen.
But by volume, the picture changes. Natural gas at standard conditions has an energy density of only about 0.036 MJ per liter. That is very low. Here is how it compares by volume:
Natural gas in its gas form takes up a huge amount of space for the energy it provides. That is why it is usually compressed or liquefied for storage and transport.
The density of natural gas changes with temperature and pressure. This is true for any gas.
Higher pressure increases density. When you compress natural gas, you pack more molecules into the same space. CNG (compressed natural gas) is stored at 3,000 to 3,600 psi. That is about 200 times atmospheric pressure. This raises its energy density to about 9 MJ per liter. Still less than gasoline, but much better than uncompressed gas.
Lower temperature increases density. When you cool natural gas to minus 162 degrees Celsius, it becomes a liquid. LNG has an energy density of about 22 MJ per liter. That is getting close to gasoline. That is why LNG is practical for long-distance shipping.
Standard conditions. Scientists use standard temperature (0 or 15 degrees Celsius) and pressure (atmospheric) when comparing fuels. Under these conditions, natural gas is about 1,000 times less dense than liquid water. That gives you an idea of how much empty space is between gas molecules.
Energy density determines what a fuel is good for.
Vehicles need high volume density. A car can only hold so much fuel. The fuel tank has a fixed size. If the fuel has low energy density, the car cannot go very far. That is why gasoline and diesel dominate transportation. They pack lots of energy into every liter.
Home heating cares less about volume density. A house has a basement or a connection to a pipeline. Space is not a problem. Natural gas works great for home heating because it is delivered continuously through pipes. The low volume density does not matter.
Aircraft need high mass density. Weight matters enormously for airplanes. Lighter fuel means the plane can carry more cargo. Jet fuel has good energy density both by weight and by volume. That makes it hard to replace with alternatives.
Shipping can use lower density fuels. Ships are huge. They have plenty of space for fuel tanks. LNG tankers carry their own fuel as LNG. The fuel takes up space, but ships have space to spare.
Imagine a backpack. If you fill it with feathers, it is light and fluffy. If you fill it with rocks, it is heavy and small. Energy density is like that. Natural gas is like the feathers. A big bag gives you lots of energy, but the bag is huge. Gasoline is like the rocks. A small bottle gives you lots of energy. That is why cars use liquid fuel. They need a lot of energy in a small space.
The energy density of natural gas explains much of the energy infrastructure around us. Pipelines exist because gas needs to be continuously supplied. The low volume density makes storage impractical for most uses. You cannot fill a tank with natural gas and expect to run your car for a week.
This is also why natural gas and renewable energy work well together. Natural gas power plants connect to pipelines that supply fuel continuously. They do not need large on-site fuel storage. That makes them easy to start and stop. A coal plant, by contrast, needs giant coal piles that burn for days or weeks.
The energy density comparison also explains the global LNG trade. Natural gas is abundant in places like Qatar, Australia, and the United States. But it is far from customers in Japan, South Korea, and Europe. Without LNG, shipping natural gas across oceans would be impossible. The volume would be too large. LNG makes it economical by increasing the energy density 600 times.
But LNG has costs. Cooling gas to minus 162 degrees Celsius uses about 10 to 15 percent of the energy in the gas. Liquefaction plants are expensive to build. Special tanker ships are expensive to operate. Still, the global LNG market has grown rapidly because the energy density problem has been solved.
The energy density of hydrogen is worth noting. Hydrogen has 120 MJ per kg, more than double natural gas. But by volume, hydrogen gas is even worse than natural gas. It has only 0.011 MJ per liter. That is one reason hydrogen vehicles are challenging. They need very high-pressure tanks or extremely cold temperatures to store enough fuel.
CNG cars. A CNG car needs a tank about four times larger than a gasoline tank to go the same distance. The tanks are heavy and take up trunk space.
LNG shipping. A typical LNG tanker carries about 170,000 cubic meters of LNG. That is enough to power about 70,000 homes for a year. Without LNG, that energy would be stranded.
Pipeline delivery. The continuous flow of natural gas through pipelines means homes never run out. There is no fuel tank to refill. The pipeline is like an unlimited fuel delivery system.
Gas storage. Natural gas is stored underground in depleted reservoirs and salt caverns. These storage facilities hold gas during summer for use in winter. The volume is enormous, but the energy density is just right for large-scale storage.
Common Misconceptions
“Energy density is the same as density.” They are different. Density is mass per volume. Energy density is energy per volume (or mass). A fuel can have high density but low energy density.
“Higher energy density always means better fuel.” Not always. A fuel also needs to be safe, affordable, and clean. Hydrogen has the highest energy density by weight, but it is hard to store and use safely.
“Natural gas has low energy density, so it is not useful.” Low volume density does not mean low usefulness. Pipeline delivery solves the volume problem. Natural gas is one of the most useful fuels in the world.
Discussion Questions
Natural gas has the highest energy density by weight of any common fossil fuel.
LNG takes up 600 times less space than natural gas. One LNG tanker holds the energy equivalent of hundreds of train cars of coal.
A kilogram of natural gas has about 50 MJ of energy. That is enough to run a microwave for about 14 hours.
CNG is stored at 3,000 to 3,600 psi. That is 200 times atmospheric pressure.
Natural gas at standard conditions is about 1,000 times less dense than water.
The energy density of natural gas drops as temperature rises. Hot gas has fewer molecules in the same volume.
Hydrogen has the highest energy density by weight of any fuel, at 120 MJ per kg. But it is very hard to store.
Energy density helps explain why oil and gas energy are used differently. Oil is a liquid with high volume density, perfect for vehicles. Natural gas is a gas with low volume density, better for stationary uses.
For more on how efficiently we use natural gas, see natural gas energy efficiency. And for the full list of advantages, visit the advantages of natural gas energy page.
To understand the basics, start with what is natural gas energy.
Last updated: June 15, 2026
What unit is commonly used for energy density?
How much more energy does LNG store per volume than natural gas?
Which fuel has the highest energy density by weight?
Why do vehicles prefer liquid fuels over natural gas?
What happens to the density of natural gas when cooled to LNG?
Answers: C: Megajoules per kilogram, C: 600 times more, C: Natural gas, B: Liquid fuels have higher energy density by volume, C: It increases by 600 times
What is energy density in simple terms?
Energy density is how much energy is stored in a given amount of fuel. A fuel with high energy density gives you more power from a smaller amount. A fuel with low energy density gives you less power from the same amount.
Does natural gas have high energy density?
Natural gas has good energy density by weight but low energy density by volume. A kilogram of natural gas contains about 50 megajoules of energy. That is similar to gasoline. But a cubic meter of natural gas contains much less energy than the same volume of liquid fuel.
How does natural gas energy density compare to gasoline?
By weight, they are similar. A kilogram of natural gas has about 50 MJ of energy. A kilogram of gasoline has about 46 MJ. But gasoline is a liquid, so it stores much more energy per liter. That is why cars use gasoline instead of natural gas.
Why is energy density important?
Energy density determines how practical a fuel is for different uses. Fuels with high energy density are better for vehicles because you can store more energy in a small tank. Fuels with lower density work fine for stationary uses like home heating.
How does liquefied natural gas (LNG) change energy density?
LNG has much higher energy density than natural gas in its gas form. Cooling natural gas to minus 162 degrees Celsius shrinks its volume by 600 times. That means 600 times more energy in the same space. That is why LNG can be shipped across oceans.
