PrintFossil Fuels account for a large portion of the world's energy sources. These fossil fuels are non-renewable fuels with a finite lifetime. So, the question is: Will we have enough supply for future energy requirements?
The answer to this question depends on the quantity of fossil fuels we have in the ground. Energy sources that have been discovered but not produced cannot be easily measured. Trapped several feet below the surface, they cannot be measured with precision. There are several terms used to report the estimates of the energy resources. The most commonly used terms are “reserves” and “resources.”
- "Reserves" represent that portion of demonstrated resources that can be recovered economically with the application of extraction technology available currently or in the foreseeable future. Reserves include only recoverable energy.
- “Resources” represent that portion of the energy that is known to exist or even suspected to exist, irrespective of technical or economic viability. So reserves are a subset of resources.
| Source of Energy | U.S. Reserves | U.S. Annual Consumption | World Reserves | World Annual Consumption |
|---|---|---|---|---|
| Petroleum (billions of barrels) |
46.4 | 7.39 | 1650 | 35 |
| Natural gas (Wet) (Trillion Cu. Ft.) |
691 | 32.1 | 6922 | 132 |
| Coal (billions of short tons) |
469 | 0.51 | 1139 | 8.56 |
SOURCES : U.S. Energy Information Administration (EIA) - Natural Gas, EIA - Coal, Worldometer - Oil left in the world
Coal
While much of the world has decreased their use of coal over the past two decades, both China and India have been increasing their use of coal. Push the play button below to show how coal usage has changed since 1900. The US was the #1 producer of coal until the 1980s, when China became #1. Since then, China's coal production has continued to increase with the exception of a small dip during COVID.
As of 2025, total world proved recoverable reserves of coal were estimated at 1139 billion short tons. In many countries, such as the US, coal consumption has been decreasing. However, in China and India, coal use has increased significantly in the past decade.
Five countries have nearly 73% of the world's coal reserves:
- United States—28%
- Russia—18%
- China—13%
- Australia—9%
- India—7%
Petroluem
Based on data from OPEC (Oil Producing and Exporting Countries), the highest proved oil reserves including non-conventional oil deposits are shown in the graphic below. This shows which regions of the world have the highes amounts of oil reserves. You can interact with this figure to show the historical change of proven reserves or create different types of charts to separate by country.
The top countries for oil resereves are Venezuela, Saudia Arabia, Canada Iran and Iraq. The US does have considerable about of oil resources and lands in the top 10 of oil producing countries.
Based on data from BP (British Petroleum), proved gas reserves were dominated by three countries: Russia, Iran and Qatar, which together held nearly half the world's proven reserves. According to the US CIA The World Factbook, the US has the 4th largest reserves of natural gas. Due to constant updates about the shale gas estimates, these are difficult to say with certainty.
How Long Will the Reserves Last?
How long these reserves do last depends on the rate at which we consume these reserves. For example, let’s assume that we have $100,000 in the bank (reserves) and if we draw 10,000 dollars every year (consumption) the reserve will last for 10 years (\$100,000/\$10,000 per year). However, in this case, we are assuming that we do not add any money to our deposit, and we do not increase our withdrawal.
This is generally not true in the case of life of an energy reserve. We may find new reserves, and our energy consumption or production can also increase. In the case of energy reserve, although we know that we might find new resources, we do not know how much we could find. But the consumption can be predicted with some accuracy based on the past rates.
Lifetime of current reserves at constant consumption
We can calculate the life of current petroleum reserves by dividing the current reserves by current consumption.
- At the current rate of consumption, the approximate lifetime of the world’s petroleum, natural gas, and coal reserves is 47.1 years, 52.4 years, and 133 years, respectively.
- At the current rate of consumption, the current U. S. petroleum, natural gas, and coal reserves will last approximately for 6.3 years, 21.5 years, and 919 years, respectively.
It is important to note that the entire U.S. petroleum consumption is not coming from the U.S. reserves because we import more than one half of the consumption. Because we import more than one half of the consumption, the petroleum reserves at the current rate will last about 11 years. If the consumption increases in the future, the life will be less. However, there is also a chance of adding more reserves with more exploration and discoveries. The increase in consumption can change depending on the price of petroleum and other alternative fuels. Likewise, us moving to electric cars and harnessing unconventional oil reserves can extend the lifetime of these reserves.
Therefore, these lifetimes are not carved in stone. It can be debated whether the U.S. reserves will last for 6 years or 10 years or even 20 years, or we may never run out! But there is increasing consensus that we must change our lifestyle. Even if we won't run out, the environmental consequences of continued use are pushing us to change anyway, but more on that later...
The R/P ratio can change from year to year, similar to our bank balance. We can add more if we make more or consume more. That changes the time we can draw on the balance.
Therefore, we must conserve, innovate (get more with less), or learn to live without these resources.