The Kardashev scale

Today

• Type 0.73

  Power of humanity

  1.9 × 10^{to the power 13} W19 trillion watts

  Humanity today is a civilization powered mostly by burning oil, coal and natural gas, with nearly all of its people and industry on the surface of its home planet.^{Source 6} Robotic spacecraft have explored every planet in the solar system, with the twin Voyager spacecraft traveling past the giant planets to the edge of interstellar space.^{Source 7} Apollo astronauts landed on the Moon 6 times between 1969 and 1972. Crews have lived aboard the International Space Station without a break since November 2000.^{Source 8,Source 9}

  Humanity's energy use, counting every fuel burned and every power plant, averaged 19 trillion watts through 2025, close to 2,300 watts for each of the 8.2 billion people on Earth.^{Source 5,Source 10}

  Supply

  Oil, coal and natural gas supplied 86 of every 100 units of that energy in 2025. Nuclear power plants, hydroelectric dams, solar panels, wind turbines and other renewable sources supplied the rest.^{Source 6}

  Science

  Deep dive into the formula

  K = (log₁₀ P − 6) ÷ 10, where P is power in watts and log₁₀ P is the power of ten equal to P.^{Source 4} Each step of 0.1 on the scale is 10 times the power. Each whole type is 10 billion times the one before. The Energy Institute reports 600.31 exajoules for 2025, where 1 exajoule is 10¹⁸ joules.^{Source 5} Dividing that total by the 31,536,000 seconds in a year gives 19.0 trillion watts. For humanity, log₁₀ of 19 trillion is 13.28, which gives (13.28 − 6) ÷ 10 = 0.73.

  A human body uses close to 100 watts, the energy in a diet of 2,000 food Calories a day, so each person's share of humanity's energy is 23 times what a body uses.^{Source 11} Of the energy delivered to users worldwide in 2022, industry used 54.6%, transport 24.8% and buildings 20.6%.^{Source 12} Data centers used 415 billion kilowatt-hours of electricity in 2024, 1.5% of the world's total.^{Source 13} Space surveillance networks tracked about 11,000 working satellites around Earth at the end of 2024.^{Source 14}

Types

1. Type I

   Power of a planet

   10^{to the power 16} W10 quadrillion watts

   Type I is a planetary civilization, one that draws power from every large source its home world offers, from sunlight over its deserts to fusion fuel in its oceans and solar collectors circling it in orbit.^{Source 1} For humanity, Type I means a civilization that lives and works across Earth, its orbit and the Moon, with factories and data centers in space and enough power to send probes toward other stars.

   Sagan set the Type I mark at 10 quadrillion watts, 525 times humanity's use today.^{Source 3,Source 5} A Type I civilization uses in 17 hours as much energy as humanity used in all of 2025.

   Supply

   Sunlight and fusion are the only sources on or near Earth large enough to reach that mark, with the sunlight striking Earth delivering 17 times the Type I power.^{Source 4} Solar panels across the deserts gather part of that light. Collectors in orbit gather more, beaming their power down to receivers on the ground.^{Source 15} Fusion, the reaction that powers the Sun, merges light atomic nuclei into heavier ones and draws its fuel from the hydrogen in seawater.^{Source 16,Source 17}

   Every watt a civilization uses ends as heat. At Type I, the heaviest users of energy, from metal refineries to data centers, work in orbit and on the Moon, where their waste heat radiates into space instead of warming Earth.

   Milestones

   On December 5, 2022, the National Ignition Facility in California released more energy from fusion than its lasers delivered to the fuel, the first time any experiment had done so.^{Source 18} Caltech's Space Solar Power Demonstrator beamed power from orbit to a receiver on Earth for the first time in 2023.^{Source 19} Starcloud-1 trained the first artificial intelligence model in orbit in December 2025.^{Source 20}

   NASA's Artemis II flew 4 astronauts around the Moon in April 2026, farther from Earth than any humans had traveled before.^{Source 21} Starship, the heavy-lift rocket SpaceX built to land and fly again, reached orbit for the first time on September 28, 2026.^{Source 22}

   Science

   Deep dive into the calculations

   The 525 times divides 10¹⁶ watts by humanity's 19.0 trillion, and the 17 hours divides the 8,760 hours in a year by 525.^{Source 5} Sunlight striking Earth delivers 170,000 trillion watts.^{Source 4} Today's solar panels convert 18% to 22% of the light falling on them into electricity.^{Source 23} The Sahara receives an average of 270 watts of sunlight on each square meter, counting nights and cloudy days.^{Source 24} Panels covering all 147.6 million square kilometers of Earth's land in sunlight that strong, at 20% efficiency, would produce 8,000 trillion watts, 80% of the mark.^{Source 25}

   Above the atmosphere, each square meter facing the Sun receives 1,361 watts.^{Source 26} Collectors supplying the whole mark from orbit at 20% efficiency, the rate of today's solar panels, cover 10¹⁶ ÷ (0.2 × 1,361) = 37 million square kilometers, one-quarter of Earth's land.^{Source 15} Perfect collectors turning all of that sunlight into power would cover 7.35 million square kilometers, close to the area of Australia. Wind turbines across every continent could extract a maximum of 18 to 68 trillion watts.^{Source 27} The tides, the heat rising from Earth's interior and the growth of every plant and alga on the planet come to less than 2% of the mark combined.^{Source 28,Source 29,Source 30,Source 31}

   Reactors on Earth fuse deuterium and tritium, 2 heavy forms of hydrogen. Every cubic meter of seawater contains 33 grams of deuterium.^{Source 17} Supplying the mark from fusion alone calls for 20 million reactors the size of ITER, each designed to release 500 million watts. Generating the full mark on Earth would add 20 watts of heat over every square meter of its surface, against 0.04 watts from humanity's energy use today, dividing each total by Earth's surface area of 510 million square kilometers.^{Source 5,Source 26}

2. Type II

   Power of a star

   10^{to the power 26} W100 trillion trillion watts

   Type II is a stellar civilization, one that collects the energy of its entire star with a swarm of solar collectors orbiting around it, the megastructure astronomers call a Dyson sphere.^{Source 1,Source 32} For humanity, Type II means a civilization spread across the solar system, building its collectors from Mercury and the asteroids and drawing its power from the Sun itself.

   Sagan set the Type II mark at 10²⁶ watts, 10 billion times the Type I mark.^{Source 3} The Sun gives off nearly 4 times that, releasing in 1 second as much energy as humanity uses in 640,000 years.^{Source 5,Source 33}

   Supply

   The physicist Freeman Dyson proposed in 1960 that a civilization in need of more energy would surround its star with structures that capture its light.^{Source 34} Artificial structures on this scale, from collectors the size of a planet to swarms that enclose a star, are known as megastructures.^{Source 35} Robotic mining spacecraft take apart asteroids and small planets for material. Factories in orbit roll that material into thin collecting sheets, each sheet circling the Sun on its own orbit.^{Source 32} The collectors glow in infrared light as they give off the heat of the power they use, so the enclosed Sun dims in visible light while still giving off its full output.

   Milestones

   NASA's Parker Solar Probe passed 6.1 million kilometers above the Sun's surface on December 24, 2024, closer than any spacecraft before it.^{Source 36} JAXA's Hayabusa2 brought samples of the asteroid Ryugu to Earth in 2020.^{Source 37} NASA's OSIRIS-REx returned 121.6 grams from the asteroid Bennu in 2023, the largest asteroid sample ever collected in space.^{Source 38} NASA's MOXIE instrument made oxygen from the air of Mars aboard the Perseverance rover between 2021 and 2023.^{Source 39}

   Astronomers search for Dyson spheres as stars that glow too brightly in infrared light. Every candidate found so far, including 7 from a 2024 survey of 5 million objects, has a natural explanation or remains unconfirmed.^{Source 40,Source 41}

   Science

   Deep dive into the calculations

   NASA measures the Sun's output at 3.828 × 10²⁶ watts, which places Sagan's Type II mark at 26% of the Sun's light.^{Source 33} The 640,000 years divides 1 second of the Sun's output by humanity's 600.31 exajoules a year.^{Source 5} Earth intercepts 1 part in 2.2 billion of the Sun's light.^{Source 4} Collectors at Mercury's distance gather 9,083 watts on each square meter, against 1,361 at Earth's.^{Source 26,Source 42} Spread across a sphere at Earth's distance from the Sun, all of Mercury's mass comes to 1.2 kilograms for each square meter.^{Source 42,Source 43}

   A 1980 NASA study designed an automated factory for the Moon able to build copies of itself from lunar material.^{Source 44} Factories that copy themselves double in number with each generation. Forty generations from 1 factory produce more than 1 trillion. In 2015 astronomers found that the star KIC 8462852, now called Boyajian's star, dimmed at irregular times by up to 20%. Measurements in 2017 matched a cloud of fine dust and ruled out a solid structure.^{Source 45,Source 46}

3. Type III

   Power of a galaxy

   10^{to the power 36} W1 trillion trillion trillion watts

   Type III is a galactic civilization, one that collects the light of the stars across its entire galaxy by building megastructures around star after star.^{Source 1} For humanity, Type III means a civilization spread across the Milky Way, star system by star system.

   Sagan set the Type III mark at 10³⁶ watts, 10 billion times the Type II mark.^{Source 3} The Milky Way's stars give off 12 times that, releasing in 1 second as much energy as humanity uses in 20 quadrillion years.^{Source 4,Source 5,Source 47}

   Supply

   Reaching billions of stars calls for machines that travel to a star, build copies of themselves from its planets and asteroids and send the copies on to the next star, the self-copying factory extended across the galaxy.^{Source 44} Light itself needs 100,000 years to cross the Milky Way, the shortest time in which such a spread could reach its far side.^{Source 47}

   Milestones

   In 2015 astronomers searched 100,000 galaxies for the infrared glow of a Type III civilization and found no galaxy converting more than 85% of its starlight into infrared heat.^{Source 48} Breakthrough Listen, a $100 million search begun in 2015, set out to listen for radio signals from the 1 million stars closest to the Sun and from the 100 closest galaxies.^{Source 49} Its 2024 study of the centers of 97 nearby galaxies found no transmitter as powerful as a Type II civilization.^{Source 50}

   Science

   Deep dive into the calculations

   The Milky Way's output of 1.2 × 10³⁷ watts comes from table 2 of the 2020 study of the scale by the astronomer Robert Gray.^{Source 4} The 20 quadrillion years divides 1 second of that output by humanity's 600.31 exajoules a year, 1.5 million times the universe's age of 13.8 billion years.^{Source 5,Source 51} The Sun lies 26,000 light-years from the galaxy's center and circles it once every 230 million years.^{Source 52,Source 53} A spacecraft at 10% of the speed of light needs 1 million years to cross the galaxy.^{Source 47}

Sources

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4. R. H. Gray, The Extended Kardashev Scale, The Astronomical Journal 159, 228, 2020.
5. Energy Institute, Statistical Review of World Energy 2026, total energy supply table, p. 23.
6. Energy Institute, Statistical Review of World Energy 2026, primary energy by source, 2025, as published by Our World in Data in its Energy mix chart.
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8. NASA, The Apollo Program, 6 lunar landing missions.
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11. U.S. Food and Drug Administration, How to Understand and Use the Nutrition Facts Label, 2024.
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14. European Space Agency, ESA Space Environment Report 2025, April 1, 2025, data to the end of 2024.
15. NASA, New Study Updates NASA on Space-Based Solar Power, January 11, 2024.
16. U.S. Department of Energy, DOE Explains: Fusion Reactions.
17. ITER Organization, Frequently Asked Questions, 500 megawatts of fusion power and 33 grams of deuterium per cubic meter of seawater, retrieved November 2, 2026.
18. Lawrence Livermore National Laboratory, Achieving Fusion Ignition, shots of December 5, 2022 and April 7, 2025.
19. California Institute of Technology, In a First, Caltech's Space Solar Power Demonstrator Wirelessly Transmits Power in Space, June 1, 2023.
20. Starcloud, Starcloud-1, and NVIDIA, How Starcloud Is Bringing Data Centers to Outer Space, October 15, 2025.
21. NASA, NASA Welcomes Record-Setting Artemis II Moonfarers Back to Earth, April 2026, 252,756 miles at the farthest point.
22. I. Klotz, On Flight 14, SpaceX Starship Reaches Orbit, Aviation Week, October 2, 2026.
23. U.S. Department of Energy, PV Cells 101: A Primer on the Solar Photovoltaic Cell, efficiency of commercial panels.
24. NASA Langley Research Center, Prediction of Worldwide Energy Resources (POWER), climatology of all-sky surface shortwave downward irradiance, 2,267 to 2,476 kilowatt-hours per square meter per year across the Sahara.
25. NASA Earthdata, Land Surface, more than 57 million square miles of land.
26. NASA National Space Science Data Center, Earth Fact Sheet, volumetric mean radius 6,371 kilometers, solar irradiance 1,361 watts per square meter and escape velocity 11.186 kilometers per second.
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28. R. D. Ray, G. D. Egbert and D. E. Smith, Tidal Energy Dissipation from Topex/Poseidon, American Geophysical Union Fall Meeting, 2000, 1 terawatt in the deep ocean and 2.6 terawatts in shallow seas.
29. J. H. Davies and D. R. Davies, Earth's surface heat flux, Solid Earth 1, 5, 2010.
30. C. B. Field, M. J. Behrenfeld, J. T. Randerson and P. Falkowski, Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components, Science 281, 237, 1998.
31. A. Yu. Borisov and L. O. Björn, On oxygen production by photosynthesis: A viewpoint, Photosynthetica 56, 44, 2018, p. 45, 3.91 × 10⁴ joules per gram of carbon.
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36. Johns Hopkins Applied Physics Laboratory, Parker Solar Probe Makes History With Closest Pass to the Sun, December 27, 2024, and NASA, After Latest Swing Past Sun, NASA's Parker Solar Probe Checks In, September 10, 2026.
37. JAXA Institute of Space and Astronautical Science, Ryugu is a primitive asteroid rich in water and organic matter, December 22, 2021.
38. NASA, NASA Announces OSIRIS-REx Bulk Sample Mass, February 15, 2024.
39. NASA Jet Propulsion Laboratory, NASA's Oxygen-Generating Experiment MOXIE Completes Mars Mission, September 6, 2023.
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42. NASA National Space Science Data Center, Mercury Fact Sheet, mass 3.3010 × 10²³ kilograms and solar irradiance 9,082.7 watts per square meter.
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