According to the International Energy Agency's World Energy Outlook 2014, if current rates of production and consumption remain constant, it is estimated that the world's proven oil reserves could be exhausted in around 50 years, known natural gas reserves in around 60 years, and known coal reserves in around 135 years. Accelerating demand for energy from developing economies could lead to these resources being depleted at an increasing rate.

Uranium, the fuel used in nuclear power stations, is also a finite resource – but there are sufficient known reserves to power a new generation of nuclear power stations. Technical advances in extraction mean uranium supplies could last for around a century.   

Renewable energy sources like the wind, sun, tides and flowing water seem inexhaustible, but current technology limits how much of their energy can be converted into electricity.

The challenge in detail

Fossil fuels are finite and will eventually run out. Renewables are seemingly inexhaustible, but harnessing them is difficult and costly. Where will our future energy come from – and how can we use it more efficiently to make it last longer?

The problem

In 2012, around 68% of electricity supplied gloabally came from fossil fuels. But fossil fuels are finite resources – eventually they will run out.

Technological advances may allow previously inaccessible 'unconventional' fossil fuel resources to be recovered – increasing the global supply – but there are concerns about the costs of accessing these resources.

Renewable energy sources are theoretically inexhaustible, but current technology limits how much of this energy can be converted into electricity. In 2012, about 21% of the electricity generated globally was from renewables. [Source: World Energy Outlook 2014]

What's being done?

Initiatives to extend our energy resources are already underway:

  • Use energy more efficiently – existing resources will last longer if we reduce demand.
  • Increase use of nuclear energy – less uranium than fossil fuels is required for large-scale electricity generation.
  • Renewable energy sources – improved technology will increase how much we convert into electricity.
  • Unconventional fossil reserves – extraction of fossil fuels such as shale gas is now more economically viable, but there are concerns about the environmental impact.

What it means for the UK

In 2009, about 73% of UK electricity was generated from fossil fuels. These are finite resources and eventually they will run out.

Production of natural gas from UK North Sea reserves is diminishing and much of our other coal reserves cannot be extracted cost-effectively. We can import these fuels, but this raises concerns about energy security.

Uranium – the fuel used in nuclear power stations – is also a finite resource, although it is abundant and has not been as heavily depleted as fossil fuels.

Wind, solar power and hydropower are all renewable energy sources, but the energy we can obtain from each is limited by our geography and the cost of the equipment needed.

The number of UK onshore sites windy enough to make a wind farm cost-effective is limited – and often meet with local opposition due to their visual impact. Offshore wind farms can harness more energy, but are expensive to construct.

Our climate and latitude, coupled with the current state of solar photovoltaic (PV) technology, make it impractical to generate electricity from solar power on a large scale. Those few UK sites with the geographical features suitable for large-scale hydroelectric power plants have already been fully exploited, leaving little potential for expansion.

How the UK is responding

The UK Government is encouraging the development of electricity generating capacity that uses energy sources other than fossil fuels. Government policy is that nuclear power will play its part in the future UK energy mix and is backing this policy with a range of steps so that new nuclear power stations can be built in time to close the energy gap.

Renewable energy sources (offshore wind turbines in particular) are also expected to contribute significantly to the future UK electricity supply. Off the coast, there is more space to build turbines than onshore, and much of this area is windy enough to make building them worthwhile. Offshore wind turbines also have less visual impact for UK residents than those onshore, so they typically generate less opposition during planning.

Government energy efficiency programmes intended to reduce greenhouse gas emissions could also reduce overall demand for electricity, helping UK fuel resources to last longer.

The quantity challenge for each energy source

Fossil fuels like coal and gas are finite resources: eventually they will run out. Renewables may seem unlimited, but exploiting their energy presents technical challenges.


As a renewable energy source, hydropower is theoretically inexhaustible, but the best sites have already been exploited.


The UK is well located to harness the movement of the sea to generate electricity. But the technologies to do so are in the early stages of development.


Our climate and latitude make the UK a less than ideal location for harnessing solar energy. But improved solar panels and using solar energy wherever possible could address these challenges.


Wind is a seemingly limitless source of energy. The biggest constraint on harnessing it is how many turbines the UK can develop, but the move offshore opens up a greater number of suitably windy sites.


Coal is a finite fossil fuel, and UK climate change commitments mean no more coal-fired power stations may be built without technology to reduce their carbon emissions.


Global gas reserves could last until around 2070 at current consumption, but that rate is likely to increase, depleting reserves more rapidly. Gas is important to UK electricity generation, and greater efficiency and a diversity of generating technologies should help to stretch gas resources further.


The biggest quantity challenge for nuclear energy is how long it takes to plan and build nuclear power stations. But Government policies to speed up construction, and better communication between energy companies, Government and the public will ease these constraints.

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