AP Syllabus focus:
‘Globally, the most widely used energy sources are fossil fuels.’
Stacked-area chart of world total energy supply by source (1971–2019), showing that coal, oil, and natural gas make up the majority of global energy supply throughout the period. It provides a clear, data-driven way to connect the “most widely used” claim to a long-run historical trend rather than a single-year snapshot. Source
Fossil fuels still power most electricity, heating, and transport worldwide because they are energy-dense, reliable on demand, and supported by decades of infrastructure, investment, and policy choices that keep them economically attractive.
Why fossil fuels dominate: core advantages
High energy density and portability
Fossil fuels store large amounts of usable energy in small volumes, which makes them easy to move, stockpile, and use across many sectors.
Energy density: The amount of energy stored in a given mass or volume of a fuel, often influencing how practical it is for transport and storage.
High energy density matters most for long-distance transport (shipping, aviation, trucking) where carrying heavy, bulky energy sources reduces payload and raises costs.
Dispatchability and controllability
Fossil-fuel power plants can be turned on, ramped up, and scheduled to match demand, making them dispatchable. This fits grids that must balance supply and demand instantly, especially where large-scale storage is limited or costly.
The “duck curve” plot shows total electricity demand, solar generation, and the remaining net load that must be supplied by dispatchable sources. It highlights the steep ramp-up required in late afternoon/early evening as solar output falls while demand rises—an intuitive visual for why flexible fossil-fuel plants have historically been valuable for grid reliability. Source
Versatility across the economy
Fossil fuels are not just used for electricity:
Industrial process heat (cement, steel, chemicals)
Space and water heating in buildings
Transportation fuels (gasoline, diesel, jet fuel)
Petrochemical feedstocks (plastics, solvents, fertilizers)
This cross-sector utility strengthens demand even when one sector (like electricity) begins to diversify.
Economic and infrastructure lock-in
Mature infrastructure and sunk costs
Existing mines, wells, pipelines, refineries, ports, power plants, and vehicle fleets create path dependence: societies keep using what their systems are built for. Replacing this infrastructure requires large upfront spending, skilled labor, permitting, and time.
Historically low market price (and priced convenience)
Fossil fuels have benefited from:
Established global supply chains and competitive markets
Large, financeable projects with predictable output
Lower short-term costs compared with building new systems
In many places, fossil fuels also receive direct and indirect subsidies, such as tax incentives, public leasing terms, or consumption subsidies that reduce end-user prices.
External costs often not included
Many negative impacts are externalities—costs imposed on society rather than paid by producers or consumers—so market prices can understate the true cost of fossil-fuel use.
Externality: A cost or benefit of an economic activity that affects third parties and is not reflected in the market price.
When air pollution, health impacts, and climate damages are weakly regulated or not priced, fossil fuels remain comparatively cheap to use.
Reliability, access, and geopolitics
Reliable supply with stockpiling
Coal piles, oil tanks, and gas storage can buffer short-term disruptions, supporting energy security goals. This reliability is especially valued for critical services (hospitals, industry, national defense) and during extreme weather demand spikes.
Uneven resource distribution and trade networks
Although fossil fuels are unevenly distributed, global trade in coal, oil, and liquefied natural gas enables many countries to import energy reliably. Long-standing trade relationships and strategic reserves reinforce continued use.
Policy, institutions, and incumbency
Energy decisions reflect regulations, utility rules, and political priorities. Fossil-fuel industries may exert influence through jobs, local tax bases, and lobbying, while governments may prioritise affordability and short-term reliability over rapid transition.
Key takeaway mechanisms to remember
Energy-dense fuels meet transport and industrial needs efficiently.
Dispatchable generation supports real-time grid stability.
Infrastructure lock-in makes switching expensive and slow.
Subsidies and unpriced externalities keep apparent costs low.
Global trade and stockpiling support dependable access.
FAQ
Long-term “take-or-pay” contracts can require buyers to pay even if they use less fuel.
This reduces financial risk for suppliers and can discourage rapid switching to alternatives.
They need very high onboard energy per kilogram and per litre.
Operational constraints (range, refuelling time, global bunkering infrastructure) make liquid fossil fuels difficult to replace quickly.
A stranded asset is infrastructure that loses value early because it becomes uneconomic or regulated out of use.
Firms and governments may resist change to avoid write-downs and job losses.
Some markets pay for “firm capacity” that can generate on demand.
Fossil plants can qualify easily, which can attract revenue beyond energy sales and keep them operating.
Higher interest rates and political risk can penalise capital-heavy projects.
Because fossil projects may have faster build times and established lenders, they can secure funding more readily in risky markets.
Practice Questions
State two reasons why fossil fuels remain the dominant global energy source. (2 marks)
Any two valid reasons (1 mark each), e.g. high energy density; dispatchability/reliability; existing infrastructure; often lower upfront cost; versatility across sectors; subsidies/unpriced externalities.
Explain how economic and system factors can reinforce continued fossil-fuel use even when alternatives exist. Include three distinct factors. (6 marks)
Any three factors explained (max 2 marks each):
Infrastructure lock-in/path dependence with sunk costs (1) plus how it slows replacement (1).
Dispatchability and grid reliability needs (1) plus limits/cost of storage and balancing (1).
Externalities not priced and/or subsidies (1) plus effect on market competitiveness and consumer behaviour (1).
