Sustainable energy is energy produced and used in such a way that it "meets the needs of the present without compromising the ability of future generations to meet their own needs." It is similar to the concepts of green energy and clean energy in its consideration of environmental impacts, however formal definitions of sustainable energy also include economic and social impacts.
The energy transition to meet the world's needs for electricity, heating, cooling, and power for transport in a sustainable way is widely considered to be one of the greatest challenges facing humanity in the 21st century. Production and consumption of energy emits over 70% of the human-caused greenhouse gas emissions that cause climate change. Worldwide, nearly a billion people lack access to electricity, and around 3 billion rely on smoky fuels such as wood, charcoal or animal dung to cook. Air pollution from fossil fuels is estimated to cause 3 million deaths each year, and air pollution from use of dirty cooking fuels is estimated to cause around 4 million deaths each year.
In general, renewable energy sources such as solar, wind, and hydroelectric energy are widely considered to be sustainable. However, aspects of some renewable energy projects, such as the clearing of forests for the production of biofuels, can lead to similar worse environmental damage than using fossil fuel energy. Nuclear power is a low-carbon source and has a safety record comparable to wind and solar, but radioactive waste and the risk of major accidents are disadvantages of this technology.
Moderate amounts of wind and solar energy, which are variable energy sources, can be integrated into the electrical grid without additional infrastructure such as grid energy storage and demand-response measures. These sources generated 8.5% of worldwide electricity in 2019, a share that has grown rapidly. Costs of wind, solar, and batteries are projected to continue falling due to innovation and economies of scale from increased investment.
Proposed pathways for limiting global warming to 1.5 °C describe rapid implementation of low-emission methods of producing electricity and heat, and a shift towards more use of electricity in sectors such as transport. The pathways also include measures to reduce energy consumption; and use of low-carbon fuels, such as hydrogen produced by renewable electricity or with carbon capture and storage. Achieving these goals will require government policies including carbon pricing, energy-specific policies, and phase-out of fossil fuel subsidies.