The Understand Energy Learning Hub is a cross-campus effort of the Precourt Institute for Energy.

Understand Energy Learning Hub

Electricity Generation

Fast Facts About
Electricity Generation

Principal Uses for Electricity: Manufacturing, Heating, Cooling, Lighting

Electricity is a high-quality, extremely flexible, efficient energy currency that can be used for delivering all types of energy services, including powering mobile phones and computers, lights, motors, and refrigeration. It is associated with modern economic activity and improved quality of life. (See our Energy for Buildings Fast Facts for additional examples of how electricity is used.)

Global electricity demand has been increasing for decades due to population growth, increased access, economic growth, and climate change (e.g., higher temperatures = more air conditioning use). Electricity demand in the United States has been relatively flat over the past decade; however, U.S. demand is expected to grow in the coming years with increased use of the internet and AI, both of which require energy-intensive data centers, and the increased adoption of new technologies like electric vehicles and heat pumps.

Two-thirds of global electricity is generated from fossil fuels in thermal power plants, where an average of 55% to 70% of resource energy is lost as waste heat. Electricity generation from cleaner renewable energy sources, particularly wind and solar PV, is rapidly increasing.

For more information about electricity, visit our The Grid: Electricity Transmission, Industry, and Markets and Decarbonization of the Electric Power Sector pages.

Key Terms

Power Plants

Baseload

Must run continuously because it takes a long time to turn them on and off

Intermediate

Used to follow demand due to their ability to ramp up and down and relatively low operating costs

Peaking

Can come online quickly to fill peaks in demand but are typically expensive to run

Intermittent

Not continuously available but often the lowest cost

Capacity Factor

Measures a power plant's utilization over a given period of time (usually a year); calculated as the ratio between the amount of energy produced and the theoretical total maximum energy production

Example: A 100 MW power plant that produces 500,000 MWh of electricity in a year

$${capacity factor} = {500,000 MWh\over{100 MW \times \frac{24 hr}{day} \times \frac{365 days}{year}}}=57\%$$

Efficiency

The percentage of fuel that a power plant converts to electricity; calculated as the ratio of energy output (electricity) to energy input

Example: A coal power plant uses 400 tonnes of coal to produce 45 MW of electricity each day. The coal has an energy content of approximately 29,000 MJ/tonne

$$efficiency = {{45 MW \times \frac{24 hrs}{day} \times \frac{3,600 MJ}{MWh}} \over {\frac{400 tonnes}{day} \times \frac{29,000 MJ}{tonne}}} = 34\%$$

Electricity Resources

Lifecycle Emissions

Total GHG emissions from a resource across its lifetime, from raw material extraction to end of life management 
Example units: gCO2e/kWh; ton CO2e/MWh

Direct Emissions

Emissions from direct use of a resource, including emissions from vehicles, fuel combustion, and fugitive emissions
Example units: gCO2e/kWh; ton CO2e/MWh

LCOE

Levelized cost of energy is calculated as the ratio of annualized cost to annualized generation and allows for the comparison of different electricity generating technologies taking into account factors like generation/output, capital costs, fuel costs, operating costs, and asset lifetimes
Example units: $/MWh
Watch this video for an example of how LCOE is calculated.

Key Attributes of Primary Electricity Resources

 

Natural Gas (Combined Cycle)

Natural Gas (Gas Turbine)

Wind

Solar PV

Coal

Nuclear

Hydro

Resource Category

fossil fuel

fossil fuel

renewable

renewable

fossil fuel

nuclear

semi-renewable

Median direct emissions (gCO2e/kWh)

370

 653

0

0

760

0

0

Median lifecycle emissions (gCO2e/kWh)

490

 data not available

11

48

820

12

24

Flexibility

intermediate

peaking

intermittent

intermittent

baseload

baseload

intermediate & intermittent

Capacity Factor (U.S. average)

59%

14%

34%

23%

42%

93%

34%

Fuel Cost

variable

variable

free

free

variable

variable

free

U.S. LCOE ($/MWh)

$45-108

 $110-228

$27-139

$29-92

$69-168

$142-222

data not available

Share of Global Electricity Generation

23%
(combined cycle & gas turbine)

8%

5%

35%

9%

14%

Global Growth (2018-2023)

8%
(combined cycle & gas turbine)

83%

185%

4%

1%

1%

World

Energy Resources Used for Electricity Generation

39%
of global primary energy resources are used to generate electricity

Pie chart showing the percentage of each type of resource used to generate electricity worldwide. Fossil fuels can be further broken down into coal, natural gas, and oil. Non-hydropower renewable sources include wind, solar, biomass, geothermal, and waste.

*Includes uncategorized generation, statistical differences and sources not specified elsewhere e.g. pumped hydro, non renewable waste and heat from chemical sources.

Percentages do not add to 100 due to rounding of individual categories.

Bar chart showing world electricity generation by region. Asia Pacific is the largest generator (15,282 TWh), mostly from coal (56%). South & Central America have the largest participation of hydro (51%). North America's electricity comes mostly from natural gas (41%).

*The Commonwealth of Independent States (CIS) consists of eleven countries from the ex-USSR: Armenia, Azerbaijan, Belarus, Kazakhstan, Kirghizstan, Moldavia, Uzbekistan, Russia, Tajikistan, Turkmenistan, Ukraine.

U.S.

Energy Resources Used for Electricity Generation

34%
of U.S. primary energy resources are used to generate electricity

Average U.S. Thermal Power Plant Efficiency

Natural gas* 44%

Coal 32%

Nuclear 33%

*For combined cycle plants

Bar chart showing electricity generation by region in the U.S. Natural gas is the primary resource used for generation throughout the country. Hydro generation is the largest in the Pacific Northwest. Solar generation is primarily coastal, while the best wind resources are in the middle of the country, from the Dakotas to Texas. Coal is mainly used in the Midwest. Nuclear plants are concentrated east of the Mississippi River.

*Biomass and geothermal are included as part of Other Renewables.

Drivers

  • High-quality energy currency: flexible and relatively efficient for end uses
  • Many resources can be used to generate electricity
  • Important for modern quality of life, reduced indoor air pollution, and human health
  • Increase in access worldwide allows for improved education and economic activity
  • Growing demand from economic and population growth
  • Increase in electrification due to demand for decarbonization
  • Distributed generation (e.g., residential rooftop solar panels) can give users more control over reliability, help manage growing demand, increase low-carbon generation, and reduce the need for grid updates

Barriers

  • Difficult and expensive to store, must match supply and demand in real time
  • Opposition due to land use impacts from transmission and distribution (NIMBY/BANANA*)

*NIMBY - not in my backyard; BANANA - build absolutely nothing anywhere near anything

Climate Impact: High*

High gradient
  • 33% of global greenhouse gas emissions come from electricity generation
  • 25% of U.S. greenhouse gas emissions come from electricity generation

Environmental Impact: High*

High gradient
  • Air pollution (SOx, NOx, air toxics, mercury)
  • Water use (cooling)
  • Water contamination (nuclear, ash ponds)
  • Thermal pollution (rivers, lakes, oceans)
  • Solid waste (ash, nuclear)
  • Land use
  • Visual
  • Noise
  • Radioactivity
  • Catastrophic failure
  • Power plant decommissioning (especially nuclear)
  • Habitat encroachment and contamination

*These impacts are dependent on the source of electricity. They are high because electricity is currently generated mainly from fossil fuels. As cleaner resources replace fossil fuels, the impacts are being reduced.

Sources
Printable PDF, 152KB

Updated October 2024

Before You Watch Our Lecture on
Electricity Generation

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential videos and readings below before watching our lecture on Electricity Generation. Include selections from the Optional and Useful list based on your interests and available time.

Essential

Optional and Useful

Our Lecture on
Electricity Generation

This is our Stanford University Understand Energy course lecture on electricity generation. We strongly encourage you to watch the full lecture to understand how electricity is generated and the significant role it plays in the global energy system. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Diana Gragg

Presented by: Diana Gragg, PhD; Core Lecturer, Civil and Environmental Engineering, Stanford University; Explore Energy Managing Director, Precourt Institute for Energy
Recorded on: April 26, 2024   Duration: 63 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Introduction 
03:48 History & Significance 
13:19 Supply Side – Electricity Generation 
47:24 Simplified Economics 
55:31 Environmental Issues 
1:00:26 What Lies Ahead

Lecture slides available upon request.

Test Your Knowledge

Additional Resources About
Electricity Generation

Stanford University

Government and International Organizations

The Grid: Electricity Transmission, Industry, and Markets Other Energy Topics to Explore

Fast Facts Sources

More details available on request.
Back to Fast Facts