Renewable Energy Sources: The 6 Main Types Compared

Six renewable energy sources supply almost all the world’s clean, renewable power: solar, wind, hydropower, geothermal, biomass and ocean energy. They differ a lot in how steady they are, what they cost and where they work best. This guide compares all six with current data from the EIA, Ember and IRENA, then links to a detailed guide for each one. If you want the bigger picture first, start at our renewable energy homepage. For the firms that build and run these plants, see the largest renewable energy companies.

What are renewable energy sources?

Renewable energy sources are energy flows that nature refills faster than people use them: sunlight, wind, flowing water, the Earth’s heat, plant matter and ocean motion. Fossil fuels and uranium are the opposite, because their stocks took millions of years to form and are finite. The IPCC’s 2011 Special Report on Renewable Energy Sources defines renewable energy as energy from solar, geophysical or biological sources that is replenished by natural processes at a rate that equals or exceeds its rate of use. Reviews such as Ellabban, Abu-Rub and Blaabjerg (2014) group the same six families used in this guide, and Jacobson and Delucchi (2011) estimated how far wind, water and solar alone could go toward supplying all global energy.

A renewable source is defined by its fuel, not by its technology. A solar panel, a wind turbine and a dam are just converters. What makes them renewable is that tomorrow the sun shines again, the wind blows again and rain refills the reservoir. For a deeper look at the definition, see our guide to renewable resources and the side-by-side renewable vs nonrenewable energy comparison.

Two related terms often get mixed up with renewables:

• Clean energy is energy with low pollution and low greenhouse gas emissions. It usually includes renewables and sometimes nuclear. Our clean energy guide covers the overlap.
• Green energy is a marketing term for renewables with the lowest environmental impact, usually solar, wind and small hydro.

What are the 6 main types of renewable energy?

The six main types of renewable energy are solar, wind, hydropower, geothermal, biomass and ocean energy. Each converts a different natural flow into electricity, heat or fuel.

1. Solar energy turns sunlight into electricity with photovoltaic (PV) panels, or into heat with solar thermal collectors and concentrating solar power (CSP) plants.
2. Wind energy uses turbine blades to turn the kinetic energy of moving air into rotation, and a generator turns that into electricity.
3. Hydropower runs water through turbines, either from a dam’s reservoir, a river’s natural flow, or between two reservoirs in pumped storage.
4. Geothermal energy taps heat from inside the Earth, using steam or hot water to drive turbines, or using shallow ground temperature to heat and cool buildings.
5. Biomass energy burns or converts organic material, such as wood, crop waste, landfill gas and manure, into heat, electricity or liquid fuels.
6. Ocean energy captures the rise and fall of tides, the motion of waves and the flow of ocean currents.

Are there 5, 7 or 10 types of renewable energy?

Lists of “5”, “7” or “10” renewable energy types describe the same handful of natural flows, split or merged differently. Five-item lists usually fold ocean energy into hydropower. Seven-item lists often separate tidal from wave energy, or add hydrogen. Ten-item lists split sources further by technology:

Longer lists may include	Where it fits in the six types
Tidal energy, wave energy, ocean thermal	Ocean energy
Solar PV, solar thermal, concentrating solar	Solar energy
Onshore wind, offshore wind	Wind energy
Biofuels (ethanol, biodiesel), biogas, landfill gas	Biomass energy
Geothermal power, ground-source heat pumps	Geothermal energy
Hydrogen	Not a source: an energy carrier made using electricity or fuels, renewable only when made with renewable power

So when a list counts 10 types, it is counting technologies, not new energy flows. Every renewable source traces back to the sun, the Earth’s internal heat, or the gravitational pull of the moon and sun on the oceans.

How much electricity comes from each renewable source?

Renewables produced 33.8% of global electricity in 2025 (Ember, Global Electricity Review 2026) and about 24% of US utility-scale electricity (EIA, 2025 data). Hydropower leads worldwide, while wind leads in the United States.

The table below combines the latest per-source figures. Global shares are from Ember’s 2025 review, which covers 2024 data, because Ember’s 2026 headline release did not break out every source.

Source	US share of utility-scale generation (EIA, 2025)	Global share of generation (Ember, 2024)	Average US capacity factor (EIA, 2025)	Global average cost of new projects (IRENA, 2024)
Wind	about 11%	8.1%	33.8%	$0.034/kWh onshore, $0.079/kWh offshore
Solar	about 7%	6.9%	24.0% PV, 23.6% solar thermal	$0.043/kWh PV, $0.092/kWh CSP
Hydropower	about 6%	14.3%	34.4%	$0.057/kWh
Biomass	about 1%	not broken out	55.8% (wood)	$0.087/kWh
Geothermal	less than 1%	not broken out	65.9%	$0.060/kWh
Ocean	negligible	negligible	not reported	not reported
All renewables	about 24%	33.8% (2025)

A few things stand out:

• Solar is growing fastest. Global solar generation rose 636 TWh, or 30%, in 2025 to 2,778 TWh (Ember). Solar also made up 511 GW of the record 692 GW of renewable capacity added worldwide in 2025 (IRENA, Renewable Capacity Statistics 2026).
• Small-scale solar is extra. EIA’s utility-scale shares exclude rooftop systems under 1 MW, which produced roughly another 0.09 trillion kWh in 2025.
• Ocean energy is still experimental at commercial scale, which is why no agency reports a meaningful share for it.

What is capacity factor and why does it matter?

Capacity factor is the electricity a plant actually produces in a year divided by what it would produce running at full power every hour. It shows how steady a source is, and it is the main reason a megawatt of solar does not equal a megawatt of geothermal.

A 1 MW plant running nonstop for a year would make 8,760 MWh. At the 2025 US averages from EIA Electric Power Monthly:

Source	Capacity factor	Approximate output from 1 MW in a year
Geothermal	65.9%	about 5,770 MWh
Wood biomass	55.8%	about 4,890 MWh
Hydropower	34.4%	about 3,010 MWh
Wind	33.8%	about 2,960 MWh
Solar PV	24.0%	about 2,100 MWh

(For comparison, US nuclear plants averaged 91.1% in 2025.) The output column is simply 8,760 hours times the capacity factor, rounded.

How does solar energy work?

Solar energy works by converting sunlight directly into electricity in photovoltaic cells, or by concentrating it into heat that drives a turbine. PV is the dominant form, used on rooftops and in large solar farms.

The physics goes back to Alexandre-Edmond Becquerel’s 1839 observation of the photovoltaic effect, and the first practical silicon cell was described by Chapin, Fuller and Pearson (1954). Shockley and Queisser (1961) later calculated the theoretical efficiency ceiling for a single-junction cell, a limit that still frames solar research today.

A photovoltaic (PV) cell is a thin wafer of semiconductor, usually silicon, that releases electrons when photons strike it. An internal electric field pushes those electrons into a circuit as direct current (DC), and an inverter converts it to the alternating current (AC) used in homes. Concentrating solar power (CSP) uses mirrors to focus sunlight on a receiver, heating a fluid that makes steam.

Solar is now the fastest-growing source of electricity in the world. Its weakness is timing: output follows the sun, so it peaks at midday and stops at night, which is why solar is increasingly paired with batteries. Read the full solar energy guide or the step-by-step explainer on how solar panels work.

How does wind energy work?

Wind energy works by using turbine blades shaped like aircraft wings to turn moving air into rotation, which spins a generator. Wind is the largest renewable source of US electricity, at about 11% of utility-scale generation in 2025 (EIA).

Power in the wind rises with the cube of wind speed, so doubling the speed gives eight times the power. That is why turbines keep getting taller, to reach steadier, faster winds, and why site choice matters so much. Onshore wind is the cheapest new source of renewable power in IRENA’s 2024 data, at $0.034/kWh. Offshore wind costs more, at $0.079/kWh, but blows harder and more steadily.

Global wind capacity reached 1,136 GW at the end of 2024 after 117 GW was added that year (GWEC, Global Wind Report 2025). See the wind energy guide for turbine parts and the power formula, and the offshore wind guide for ocean projects.

How does hydropower work?

Hydropower works by letting water fall or flow through a turbine, usually from a dam’s reservoir down to the river below. It is the world’s largest renewable source, at 14.3% of global electricity in 2024 (Ember).

There are three common designs:

• Impoundment (dam): a reservoir stores water and releases it through turbines when power is needed.
• Run-of-river: a portion of a river’s flow is diverted through turbines with little or no storage.
• Pumped storage: water is pumped uphill when power is cheap and released through turbines when it is needed, acting as a giant battery.

Hydropower can ramp up and down in minutes, so grid operators use it to balance solar and wind. Its limits are geography, droughts and the ecological cost of damming rivers. Our hydroelectric power guide covers these trade-offs.

How does geothermal energy work?

Geothermal energy works by drilling into underground reservoirs of steam or hot water and using that heat to spin turbines. Geothermal power plants need very hot water or steam, roughly 300°F to 700°F (about 150°C to 370°C), according to the EIA.

There are three plant types: dry steam, flash steam (the most common) and binary cycle, which uses a second fluid with a lower boiling point. Because the Earth’s heat never switches off, US geothermal plants ran at a 65.9% capacity factor in 2025, the highest of any renewable source.

Its share is small, under 1% of US generation, because good reservoirs are concentrated in a few places such as California and Nevada. Enhanced geothermal systems, which create reservoirs in hot dry rock, could widen that map. The geothermal energy guide explains each plant type, and the geothermal heat pump guide covers the very different home heating technology.

What is biomass energy?

Biomass energy is energy from organic material, such as wood, agricultural residues, landfill gas, manure and energy crops. It can be burned for heat and power, digested into biogas or refined into biofuels like ethanol and biodiesel.

Biomass is renewable because plants regrow, but it is the most debated renewable. Burning it releases carbon dioxide and air pollutants at the point of use, and its climate benefit depends on how fast the feedstock regrows and what would have happened to it otherwise. Its strength is that it is dispatchable: US wood-fired plants averaged a 55.8% capacity factor in 2025 (EIA). IRENA’s 2024 global average cost for new bioenergy power was $0.087/kWh, up 13% on 2023. Read more in our biomass energy guide.

What is ocean energy?

Ocean energy is power captured from tides, waves, ocean currents and temperature differences in seawater. It is the least developed of the six renewable sources and produces a negligible share of electricity today.

Tidal energy is highly predictable, since tides follow the moon, which is its main appeal. Tidal barrages work like low dams across estuaries, while tidal stream turbines sit on the seabed like underwater wind turbines. Wave energy converters ride the surface motion of the sea. The challenge for all of them is cost and durability in salt water and storms. Our tidal and wave energy guide covers the main designs.

History of renewable energy sources

Every renewable source on this list was harnessed for electricity between 1880 and 1966, long before “renewables” became a policy category. Hydropower came first, then wind and geothermal; solar cells arrived in the 1950s and the first tidal plant in the 1960s.

Hydropower was the first to make electricity at scale: in 1880 a water turbine drove a dynamo that lit a theater and storefront in Grand Rapids, Michigan (US DOE). Wind followed in 1888, when Charles Brush built a 12 kW automatically operated turbine to charge batteries at his Cleveland home; James Blyth in Scotland had generated wind power a year earlier (Mills Archive). In 1904 Piero Ginori Conti lit five bulbs with geothermal steam at Larderello, Italy, and by 1913 the world’s first geothermal power plant was running there (ThinkGeoEnergy).

Solar took longer because the physics had to catch up. Becquerel saw the photovoltaic effect in 1839, but a useful cell only came when Bell Labs demonstrated a silicon cell of about 6% efficiency on April 25, 1954; solar cells then powered satellites from Vanguard 1 in 1958 (IEEE Milestone). Ocean energy reached the grid when France’s 240 MW La Rance tidal barrage opened on November 26, 1966 (PNNL Tethys), and wind went to sea with Denmark’s Vindeby farm in 1991 (WindEurope).

The 1970s oil shortages turned these technologies from curiosities into policy, creating interest in wind and other alternatives (EIA). The US PURPA law of 1978 then required utilities to buy power from small independent producers, including renewable plants (IEA).

Year	Milestone	Source
1839	Becquerel observes the photovoltaic effect	APS News
1880	Water-driven dynamo lights a Grand Rapids theater	US DOE
1888	Brush’s 12 kW wind turbine, Cleveland	Mills Archive
1904	First geothermal electricity, Larderello	ThinkGeoEnergy
1913	First geothermal power plant, Larderello	ThinkGeoEnergy
1954	Bell Labs silicon solar cell (about 6%)	IEEE Milestone
1966	La Rance tidal power station opens, 240 MW	PNNL Tethys
1978	PURPA creates a market for independent renewable power	IEA
1991	Vindeby, the first offshore wind farm	WindEurope
2025	Renewables pass coal in global electricity	Ember

Which renewable energy source is best?

No single renewable source is best everywhere: onshore wind and solar are cheapest, while geothermal, hydro and biomass are steadiest. Most grids combine several sources so each covers the others’ gaps.

Use this quick guide to match a source to a need:

If you need…	Best-fit sources	Why
The lowest cost per kWh	Onshore wind, solar PV	Lowest global averages in IRENA’s 2024 data
Power day and night	Geothermal, hydropower, biomass	Dispatchable or near-constant output
Power for a home	Rooftop solar, plus battery	Modular, quiet and installed on existing roofs
Fast grid balancing	Hydropower, pumped storage	Can ramp within minutes
Large output near coasts	Offshore wind	Strong, steady winds at sea

For the trade-offs in more detail, see advantages of renewable energy, solar energy pros and cons and wind energy pros and cons.

Which renewable energy sources can you use at home?

Homeowners can use rooftop solar panels, small wind turbines and geothermal heat pumps. Solar is by far the most common because it works on almost any sunny roof and needs no moving parts.

1. Measure your use. Find your annual kWh on your electric bill or with our electricity usage calculator.
2. Size a solar array. Enter your use and location into the solar panel calculator to get panel count and system size.
3. Optimize panel tilt. The solar panel angle calculator gives the best tilt for your latitude.
4. Check wind if you have open land. A home wind turbine only makes sense with steady wind and few obstacles; estimate output with the wind turbine calculator.
5. Consider geothermal for heating. A ground-source heat pump cuts heating and cooling energy rather than generating electricity.

Are renewable energy sources really unlimited?

Renewable energy sources are effectively unlimited in fuel, but not in the land, materials and sites needed to capture them. The sun and wind will not run out, yet the best wind sites, rivers and geothermal reservoirs are finite.

Each source has physical limits. Hydropower depends on rainfall and suitable valleys. Biomass is only renewable if harvest rates stay below regrowth. Geothermal reservoirs can cool if heat is extracted faster than it is replaced, which is why plants reinject water underground. Solar panels and wind turbines need metals, glass and concrete, and their recycling is still scaling up. None of these limits comes close to the finite stock of coal, oil, gas or uranium, which are covered in our guide to non-renewable resources.

Scientific references

• IPCC (2011). Renewable Energy Sources and Climate Change Mitigation: Special Report of the Intergovernmental Panel on Climate Change (O. Edenhofer et al., eds.). Cambridge University Press. doi:10.1017/CBO9781139151153
• Chapin, D. M., Fuller, C. S., & Pearson, G. L. (1954). “A New Silicon p-n Junction Photocell for Converting Solar Radiation into Electrical Power.” Journal of Applied Physics, 25(5), 676–677. doi:10.1063/1.1721711
• Shockley, W., & Queisser, H. J. (1961). “Detailed Balance Limit of Efficiency of p-n Junction Solar Cells.” Journal of Applied Physics, 32(3), 510–519. doi:10.1063/1.1736034
• Jacobson, M. Z., & Delucchi, M. A. (2011). “Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials.” Energy Policy, 39(3), 1154–1169. doi:10.1016/j.enpol.2010.11.040
• Ellabban, O., Abu-Rub, H., & Blaabjerg, F. (2014). “Renewable energy resources: Current status, future prospects and their enabling technology.” Renewable and Sustainable Energy Reviews, 39, 748–764. doi:10.1016/j.rser.2014.07.113
• Hsu, D. D. et al. (2012). “Life Cycle Greenhouse Gas Emissions of Crystalline Silicon Photovoltaic Electricity Generation: Systematic Review and Harmonization.” Journal of Industrial Ecology, 16(S1), S122–S135. doi:10.1111/j.1530-9290.2011.00439.x

Bottom line

Renewable energy sources supplied 33.8% of the world’s electricity in 2025 and about a quarter of US utility-scale power. Hydropower is still the global leader, wind leads in the US, and solar is growing fastest by far. Onshore wind and solar are the cheapest new power, while geothermal, hydro and biomass offer the steadiest output. Pick the guide for the source you care about, or size your own system with the solar panel calculator.