The term resource refers to the total amount of a material or primary energy flow that exists in nature. To emphasize where these resources come from they're often referred to as natural resources. This includes material that is both discovered and undiscovered, economically recoverable or not economically recoverable. While this encyclopedia focuses mostly on fuel resources, natural resources include other raw materials that come from nature like copper or aluminum in the form of ores.

From an energy perspective, primary fuels such as coal, oil, natural gas, and uranium are material resources. Flows in nature like wind, and hydro are also natural resources. Since resources include undiscovered fuel deposits, there is a certain level of uncertainty of how much of a resource there actually is.[1] This does not mean that there is no way to estimate the size of these natural resources, the total amount of a resource can be described and estimated based on information obtained from surveys.[2]

The fact that coal, oil, and natural gas are referred to as non-renewable resources can be confusing, as it makes it sound as if these resources are running out soon. It is true that fossil fuel reserves are predicted to decline in the future, (see Hubbert's peak for some description of this). However vast resources will still remain simply because there is likely so much undiscovered or inaccessible fuel.[5]

Reserve vs. Resource

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Although both resources and reserves refer to some amount of a mineral or fuel, they are not the same thing and should not be confused as they are very different. This difference can be explored using a McKelvey diagram. McKelvey diagrams portray information about how a resource can turn into a reserve over time with effort.

Types of Resources

Resources contain a large amount of energy sources, so it is sometimes easier to divide the resource as a whole into smaller pieces to understand why it is not a reserve. The types of resources that exist are:[2]

  • Identified Resource: This resource is one that has been measured to the point where the amount that exists can be quantified or estimated reasonably well. As well, estimates exist for how much more of this resource are available. Identified resources have been measured well enough that there is some level of confidence in predictions about how much exists, and this confidence is usually acquired after surveying large areas around the world thoroughly. These resources may or may not be accessible.
  • Undiscovered Resource: This is the amount of a resource that is unknown and cannot be estimated. This portion includes part of the resource that are assumed to exist but cannot be measured either because they have not been explored or are in inaccessible areas.

Combined, the identified and undiscovered amounts for a resource are the total resource. Although some resources may be currently undiscovered or inaccessible, it is possible in the future that further exploration and advances in technologies could allow these resource to become known and economically viable. If this occurs, the worlds reserves will become larger.[5]


  1. Richard Wolfson. (May 29, 2015). Energy, Environment, and Climate, 2nd ed. New York, NY, U.S.A: 2012.
  2. 2.0 2.1 Sarah Friedl. (May 29, 2015). Resources and Reserves: Definitions and Examples [Online]. Available:
  3. Pixabay. (May 29, 2015). Drilling Tower [Online]. Available:
  4. Pixabay. (May 29, 2015). Rotor Pinwheel [Online]. Available:
  5. 5.0 5.1 G.Boyle, B.Everett, S.Peake, J.Ramage. (May 29, 2015). Energy Systems and Sustainability: Power for a Sustainable Future, 2nd Ed. Oxford, UK: Oxford University Press, 2012

Authors and Editors

Jordan Hanania, Kailyn Stenhouse, Jason Donev