Renewable energy converts natural flows — sunlight, wind, water and heat — directly into electricity using turbines, photovoltaic cells and generators, without burning fuel. In 2025, renewables supplied 34% of the world's electricity, up from 23% a decade earlier, and are on track to overtake coal as the single largest power source, according to the International Energy Agency.
Renewable energy comes from sources that replenish naturally on a human timescale — sunlight, wind, flowing water, heat inside the Earth and organic matter. Unlike coal, oil, gas or nuclear fuel, these sources are not burned or consumed; power plants instead capture energy that is already moving through the environment and turn it into electricity.
How each technology converts nature into electricity
Wind turbines use blades shaped like airplane wings. As wind passes over them, the difference in air pressure on each side creates lift, which spins a rotor. The rotor turns a generator — either directly or through a gearbox that speeds up the rotation — and that mechanical spinning produces electricity, which is sent to the grid through a substation, according to the U.S. Department of Energy.
Solar panels work differently: they contain no moving parts. Silicon solar cells are treated so that one layer carries a positive charge and another a negative charge. When sunlight hits the cell, photons knock electrons loose, and this flow of electrons — the photovoltaic effect — creates direct-current (DC) electricity. Because homes and most grids run on alternating current (AC), an inverter converts the power before it is used.
Hydropower plants use the force of falling or flowing water to spin a turbine connected to a generator, the same basic principle as wind but using water's weight and movement instead of air. Geothermal plants tap heat stored underground to produce steam that drives a turbine, while bioenergy plants burn organic material such as crop waste or wood to generate heat that is converted into electricity.
Renewables are closing in on coal
According to the International Energy Agency's Global Energy Review, renewables supplied 34% of global electricity generation in 2025, up from 32% in 2024 and 23% a decade earlier. Combined with nuclear power, low-emissions sources reached 43% of global generation in 2025 — the highest share in fifty years, the IEA said.
Solar PV alone added about 600 terawatt-hours of generation in 2025, its largest annual increase ever, the IEA reported. Wind and solar together reached 17% of global electricity generation, up from roughly 5% a decade ago. The IEA said global renewable generation "virtually matched" coal-fired generation in 2025, while coal generation itself fell by around 0.5% — its first decline outside a crisis period since 2015.
Why variability is the central engineering challenge
Wind and solar output rises and falls with weather and daylight, so grid operators need other tools to keep supply matched to demand at every moment.
Batteries have become one of the main tools used to smooth out these swings. Global battery storage capacity additions reached 108 GW in 2025, around 40% higher than in 2024, according to the IEA. China added just over 63 GW and the United States 19 GW, a 60% year-on-year increase. In California, battery storage has gone from supplying less than 1% of hour-to-hour grid-balancing needs five years ago to more than 60% in the first quarter of 2026, the IEA said.
What comes next
The IEA projects that 4,600 GW of new renewable capacity will be installed worldwide between 2025 and 2030 — roughly double the total added in the previous five years — with solar PV accounting for nearly 80% of that growth. Global renewable electricity generation is forecast to rise 60%, from 9,900 terawatt-hours in 2024 to 16,200 terawatt-hours in 2030, pushing the renewable share of world electricity to 43%.
Renewable generation virtually matched coal-fired generation in 2025.
— International Energy Agency, Global Energy Review 2026
Questions
What counts as renewable energy?
Sources that replenish naturally and are not consumed when used for power, mainly sunlight (solar), wind, flowing water (hydropower), underground heat (geothermal) and organic matter (bioenergy).
What share of the world's electricity comes from renewables today?
Renewables supplied 34% of global electricity generation in 2025, up from 32% in 2024 and 23% a decade earlier, according to the IEA's Global Energy Review.
How do solar panels actually make electricity?
Sunlight hitting treated silicon cells knocks electrons loose, creating a flow of direct-current electricity (the photovoltaic effect); an inverter then converts it to the alternating current used by homes and grids.
Why is battery storage important for renewable energy?
Because wind and solar output varies with weather and daylight, batteries store excess power and release it on demand, helping grid operators balance supply and demand; global battery additions grew about 40% in 2025, per the IEA.
Will renewables overtake coal as the world's top electricity source?
The IEA reported that global renewable generation virtually matched coal-fired generation in 2025 and projects renewables will reach 43% of global electricity generation by 2030, well above coal's declining share.
This piece was prepared with artificial intelligence and passed an automated source check before publication. If you see an error, ask for a correction. Request a correction or reply · How we make this
Photosynthesis is the process by which plants, algae and some bacteria use sunlight, water and carbon dioxide to make sugar and oxygen. It happens in two linked stages inside chloroplasts: light-dependent reactions that capture solar energy, and the Calvin cycle that uses that energy to build carbohydrates.
Vaccines work by showing the immune system a harmless piece of a pathogen — called an antigen — so the body builds antibodies and memory cells without suffering the actual disease. Getting a vaccine to that point takes years of preclinical testing and three phases of human trials before regulators such as the FDA license it. Full protection after vaccination typically takes a few weeks, as the immune system needs time to produce lasting defenses.
Warhound, co-founded by Colossal Biosciences' Ben Lamm and Anduril's Palmer Luckey, raised $200 million on October 22, 2026 to genetically edit and clone dogs for the US military, aiming to remove inherited diseases from breeds such as the Belgian Malinois. Independent scientists call the genetic goals technically achievable, but bioethicists warn that cloning remains inefficient and raises unresolved animal-welfare and regulatory questions.
Leap seconds, the one-second adjustments used since 1972 to keep clocks aligned with Earth's rotation, will stop entirely. The world's timekeeping authority, the International Bureau of Weights and Measures (BIPM), confirmed on 15 October 2026 that continuous UTC takes effect on 20 May 2027. The move, first agreed in principle in 2022, was accelerated after experts flagged a growing risk of a disruptive "negative" leap second.
