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What is renewable energy?
Renewable energy is energy produced from natural sources that replenish themselves faster than they are consumed — sunlight, wind, flowing water, organic matter and the heat of the Earth. Unlike fossil fuels such as coal, oil and natural gas, these sources are virtually inexhaustible on a human timescale and emit little to no greenhouse gases.
Just like fossil fuels, renewable sources can produce electricity, heat, gas and fuel (called biogas and biofuel respectively). Developing them is one of the pillars of the energy transition and the fight against global warming, because it cuts the emissions responsible for the greenhouse effect.
Renewable vs non-renewable energy
Non-renewable energy comes from resources that exist in finite quantities and cannot regenerate on a human timescale: coal, oil, natural gas and uranium. Burning fossil fuels is the main cause of man-made CO2 emissions. At the current rate of global consumption, proven oil and gas reserves would last only a few more decades, and coal and uranium reserves around a century.
| Criterion | Renewable energy | Non-renewable energy |
|---|---|---|
| Source | Naturally replenished (sun, wind, water, biomass, Earth’s heat) | Finite reserves (coal, oil, gas, uranium) |
| Availability | Inexhaustible, though sometimes intermittent | Depleted as it is extracted |
| CO2 emissions | Zero or very low during generation | High for fossil fuels |
| Examples | Solar, wind, hydro, biomass, geothermal, marine | Coal plants, gas-fired plants, nuclear |
Renewable, green or low-carbon: what is the difference?
These three notions are close but do not overlap exactly. A green energy is both renewable and clean, while a low-carbon energy simply emits little or no CO2 when it is produced — whether it is renewable or not.
| Notion | Criterion | Examples |
|---|---|---|
| Renewable energy | The source regenerates naturally and continuously | Solar, wind, hydro, biomass, geothermal |
| Green energy | Renewable AND clean (very low pollution) | Green electricity, biogas |
| Low-carbon energy | Emits little or no CO2, without necessarily being renewable | Nuclear, but also all renewables |
What are the 5 main types of renewable energy?
Renewable energy comes mainly from five natural sources: the sun, the wind, water, biomass and the heat of the Earth — to which marine energy can be added as an emerging sixth family. Here are the five main types:
- Solar energy, the fastest-growing source of electricity in the world
- Wind energy, harvested onshore and offshore
- Hydropower, still the largest single renewable source
- Biomass and biogas, from organic matter
- Geothermal energy, a renewable that never stops
Solar energy: photovoltaic and thermal
Solar energy harnesses the electromagnetic radiation of the sun. It is exploited in two ways:
- Photovoltaic solar energy, which converts light into electricity through solar panels — or building-integrated alternatives such as solar tiles;
- Solar thermal energy, which uses collectors to heat a fluid, from domestic hot-water systems to concentrated solar power plants such as Noor Ouarzazate in Morocco.
Solar is the fastest-growing source of electricity in the world: its generation jumped by 30% in 2025 and met three quarters of the growth in global electricity demand, according to Ember. The reason is economic: the cost of generating a solar kWh has fallen by around 90% since 2010, making photovoltaics one of the cheapest sources of new electricity, according to IRENA. Giant solar parks such as Bhadla in India now stretch over tens of square kilometres.
Wind energy: onshore and offshore
Wind energy captures the kinetic energy of the wind: turbines convert the movement of their blades into electricity. Like solar, it is inexhaustible but intermittent, since output depends on how hard the wind blows. Turbines can be installed in two settings:
- Onshore wind turbines, which are simpler and cheaper to install — Whitelee Wind Farm near Glasgow, the largest in the UK, counts more than 200 turbines;
- Offshore wind turbines, which benefit from stronger, steadier sea winds and produce more electricity — the Hornsea projects off the English coast are among the largest offshore wind farms in the world.
Wind has expanded rapidly over the last twenty years and generated 8.5% of the world’s electricity in 2025. Because no region is windy all the time, grids combine it with other sources — and increasingly with storage — to keep supply steady.
Hydropower
Hydroelectric power, also known as hydropower, converts the movement of water — dams, rivers, waterfalls — into electricity through turbines. The greater the flow and the height of the drop, the more energy is produced, which makes output dependent on rainfall. Thanks to the water cycle, it is a fully renewable and highly controllable source, and pumped-storage plants such as Dinorwig in Wales even act as giant batteries for the grid.
Hydro remains the largest single renewable source of electricity in the world, supplying around 14% of global generation in 2025. The Itaipu dam between Brazil and Paraguay is one of the most powerful plants on the planet, and countries such as Norway, Paraguay and Costa Rica cover almost all of their electricity needs with water.
Biomass and biogas
Biomass energy comes from organic matter of plant or animal origin. Its two main techniques are the combustion of wood and agricultural residues, and anaerobic digestion (methanisation), in which fermenting organic waste produces biogas. Biomass can generate electricity, heat or fuel, and it only counts as renewable if the resource is not consumed faster than it regrows.
Concrete examples abound: sugar mills burn cane bagasse to power their operations, farms digest slurry and crop residues, and plants like the Veolia biogas facility in North Yorkshire inject biomethane into the gas grid to supply thousands of homes. Together with geothermal and other sources, bioenergy provided around 2.6% of the world’s electricity in 2025 — and far more of its heat.
Geothermal energy
Geothermal energy extracts the heat stored beneath the Earth’s surface. Depending on the depth and temperature, it can produce electricity in volcanic areas or heat buildings directly — including through ground-source heat pumps that work almost anywhere.
Along with biomass, it is one of the only renewables that is not intermittent: it delivers day and night, whatever the weather. The world’s oldest geothermal field, at Larderello in Tuscany, has been producing electricity since 1913, and Iceland covers most of its heating needs with geothermal energy.
Advantages and disadvantages of renewable energy
Advantages of renewable energy
- Inexhaustible and free sources: the sun, the wind and water cannot be bought, imported or depleted;
- Little to no greenhouse gas emissions during generation, which makes renewables the main tool against climate change;
- Rapidly falling costs: solar power is around 90% cheaper than in 2010, and solar and onshore wind are now the cheapest sources of new electricity in most of the world (IRENA);
- Greater energy independence: producing locally reduces imports of oil and gas and exposure to price shocks;
- Local jobs in installation and maintenance that cannot be offshored.
Disadvantages of renewable energy
- Intermittency: solar and wind only produce when the sun shines or the wind blows, and hydro output falls in dry years;
- The need for storage and more flexible grids (batteries, pumped hydro, interconnections) to smooth out this variable output;
- A high upfront investment for some installations (dams, offshore wind farms, deep geothermal);
- Possible local impacts on landscapes and biodiversity (reservoirs, wind farms, land use), which must be managed case by case.
Renewable energy in the world: the 2025 figures
2025 was a historic year. Renewables generated 33.8% of the world’s electricity and overtook coal (33.0%) for the first time in a century, according to the Global Electricity Review by Ember. Solar and wind together met 99% of the growth in global electricity demand, and fossil fuel generation actually fell — the first structural decline on record.
On the capacity side, the world installed a record 692 GW of new renewable capacity in 2025, bringing the global total to 5,149 GW, according to IRENA. Solar alone accounted for roughly three quarters of these additions, and solar and wind together made up 97% of them.
| Technology | Share of world electricity | Trend |
|---|---|---|
| Hydropower | 14% | Stable: the largest single renewable source |
| Solar | 8.7% | +30% in 2025: the fastest-growing source |
| Wind | 8.5% | Steady growth, onshore and offshore |
| Bioenergy, geothermal and others | ≈2.6% | Moderate growth |
| All renewables | 33.8% | Above coal for the first time |
Governments are pushing to accelerate. At COP28, nearly 200 countries pledged to triple global renewable capacity by 2030. The European Union’s RED III directive requires at least 42.5% renewables in final energy consumption by 2030, the UK is legally bound to reach net zero by 2050, India is targeting 500 GW of non-fossil capacity by 2030 and Morocco aims for 52% renewable electricity capacity by the same date.
Switching to a renewable energy supplier
You do not need to build a wind farm to support renewables. In liberalised electricity markets, any household can choose a green tariff: for every kWh you consume, your supplier guarantees that a kWh of renewable electricity is injected into the grid, certified by guarantees of origin. Our guide to green energy suppliers compares the main offers.
Switching to green energy can help reduce your electricity bills and cut your carbon footprint at the same time — green tariffs are not always more expensive than standard ones. You can also generate your own power with solar panels, or go further by supporting a certified carbon offsetting project.