Using 100% renewable energy means meeting all energy needs, such as electricity, heating, cooling, and transportation, with resources that can be naturally replenished. This goal is driven by concerns about greenhouse gas emissions, pollution, environmental harm, and issues related to energy security and economic stability. Changing the global energy system to rely fully on renewable sources is necessary because most current energy comes from non-renewable fossil fuels.

Research on this topic began recently, with few studies published before 2009, but interest has grown significantly in recent years. A key feature of 100% renewable energy systems is a cross-sectoral approach, which considers how different parts of the energy system—such as electricity, heat, transport, and industry—work together. This method is based on the idea that the best solutions are found by focusing on how these areas can support each other.

Feasibility

There is no single, agreed-upon definition for 100% renewable energy systems in scientific studies. Recent research shows that switching to 100% renewable energy in all areas—such as electricity, heating, transportation, and water desalination—before 2050 is possible. A review of 181 scientific papers published by 2018 found that most studies show 100% renewable energy systems are technically possible and cost-effective. A review of 97 papers published since 2004, which focused on islands, found that 100% renewable energy is also technically possible and cost-effective. A 2022 review concluded that most research in the field agrees that 100% renewable energy is feasible worldwide at low cost.

Current technologies, including energy storage, can provide a reliable energy supply every hour of the year. A sustainable energy system using renewable sources is more efficient and less expensive than the current system. The United Nations Intergovernmental Panel on Climate Change (IPCC) stated in a 2011 report that there are few barriers to using renewable technologies to meet the world’s total energy needs.

Mark Z. Jacobson, a professor at Stanford University and director of its Atmosphere and Energy program, says it is possible to produce all new energy using wind, solar, and hydropower by 2030. He believes current energy systems could be replaced by 2050. He says the main challenges to this plan are social and political, not technological or economic. Jacobson claims that energy costs using wind, solar, and water systems would be similar to current energy costs. He has responded to criticism of his work, saying the critics were influenced by their support for energy technologies not included in a 2015 study.

In 2022, Jacobson and others published a study showing how 145 countries could achieve 100% renewable energy by 2035 and 2050. The study found that a wind, water, and solar system would use less energy, cost less, and create more jobs than current energy systems. The cost savings were mainly due to a 56.4% decrease in overall energy demand, caused by using renewable electricity more efficiently.

In 2014, renewable energy sources like wind, geothermal, solar, biomass, and waste provided 19% of the world’s total energy use, with about half coming from traditional biomass use. Electricity is the largest energy sector, with 22.8% of its energy coming from renewables, mostly from hydropower (16.6%) and wind (3.1%). By 2018, renewable energy use in electricity was growing faster than expected, but more action is needed in heating, cooling, and transportation.

Many areas around the world already use grids powered mostly by renewable energy. At least 30 countries have renewable energy contributing more than 20% of their total energy supply. Renewable energy use has grown faster than even supporters predicted. However, as of 2019, renewable energy needs to grow six times faster to limit global warming to 2°C (3.6°F).

A 100% renewable energy system uses only energy from renewable sources for electricity, heating, cooling, and transportation. This goal is driven by concerns about global warming, pollution, and energy security. Switching to renewable energy requires changing the current energy system, as most energy today comes from non-renewable fossil fuels.

The IPCC says there are few major technological limits to using renewable energy to meet most of the world’s energy needs. Renewable energy use has grown faster than expected, but it needs to grow six times faster by 2019 to limit global warming to 2°C (3.6°F).

Achieving 100% renewable energy in a country is more difficult than achieving carbon neutrality, which is a climate goal set by many countries. Carbon neutrality can be reached by balancing a country’s total carbon footprint with carbon removal efforts or projects in other countries.

By 2018, renewable energy use in electricity was growing faster than expected, but urgent action is needed in heating, cooling, and transportation. Many areas globally already use grids powered mostly by renewable energy. At least 30 countries have renewable energy contributing more than 20% of their total energy supply.

A review of 181 scientific papers on 100% renewable energy published by 2018 found that most studies show these systems are technically possible and cost-effective. While many studies focus only on electricity, more recent research covers other energy sectors and integrated systems that connect electricity, heat, transport, and industry. This cross-sector approach is seen as important because it considers how different areas of the energy system work together.

Stephen W. Pacala and Robert H. Socolow of Princeton University created a plan called "climate stabilization wedges" to help reduce climate change while maintaining quality of life. Renewable energy sources make up the largest number of these wedges.

In the United States, the National Research Council noted that enough renewable resources exist to help meet future electricity needs and address climate change, energy security, and rising energy costs. Renewable energy is a good option because the total renewable resources in the U.S. can produce more electricity than current or projected demand.

The main barriers to using large-scale renewable energy and low-carbon strategies are political, not technological. A 2013 report found that key challenges include climate change denial, the fossil fuels industry, political inaction, high energy use, outdated energy systems, and financial limits.

Studies show that countries in Southeast Asia could achieve nearly 100% renewable electricity using solar, wind, and off-river pumped hydro storage at a cost of about US$55–115 per megawatt-hour.

History

The idea of using 100% renewable energy was first suggested in a paper published in Science in 1975 by Danish physicist Bent Sørensen. This was followed by other proposals. In 1976, energy policy analyst Amory Lovins introduced the term "soft energy path" to describe a future where energy efficiency and renewable energy sources could replace a system that relies on fossil fuels and nuclear power.

In 1998, the first detailed analysis of scenarios with high shares of renewable energy was published. These were followed by the first detailed 100% renewable energy scenarios. In 2006, a PhD thesis by Czisch showed that in a 100% renewable energy scenario, energy supply could match demand every hour of the year in Europe and North Africa. That same year, Danish energy professor Henrik Lund published a paper about the best way to combine renewable energy sources. He later wrote many more papers on transitioning to 100% renewable energy in Denmark. Since 2009, the number of publications on 100% renewable energy scenarios has grown rapidly, covering countries in Europe, America, Australia, and other regions.

In the early 21st century, it was unusual for scientists and leaders to consider the idea of 100% renewable electricity. However, renewable energy has grown much faster than expected. For example, wind turbines now provide 39% of Denmark’s electricity. Wind and biomass together supply 44% of Denmark’s electricity for its six million people. In 2010, Portugal’s 10 million people produced more than half their electricity from local renewable sources. Spain’s 40 million people meet one-third of their electricity needs from renewables.

Renewable energy has strong public support. In America, a 2013 Gallup survey found that two-thirds of Americans support increasing domestic energy production using solar power (76%), wind power (71%), and natural gas (65%). Fewer people support increasing production of petroleum (46%) or nuclear power (37%). Coal is the least supported, with about one-third of Americans favoring it.

REN21 reports that renewable energy already plays an important role, and many policies aim to increase its use. Supporters of 100% renewable energy do not consider nuclear power or carbon capture and storage as renewable or sustainable due to risks and limitations. These concerns have increased interest in 100% renewable energy. Over the past decade, many studies have evaluated 100% renewable energy scenarios for different regions. Recently, more detailed analyses have come from governments and industries. The push for 100% renewable energy is driven by global warming, ecological and economic concerns, and the end of easily accessible oil.

Iceland was the first country to propose 100% renewable energy in 1998. Other countries, like Japan (2003) and Australia (2011), later made similar proposals. Albania, Iceland, and Paraguay get nearly all their electricity from renewable sources (Albania and Paraguay use 100% hydroelectricity; Iceland uses 72% hydro and 28% geothermal). Norway gets nearly all its electricity from renewable sources (97% from hydropower). Iceland proposed using hydrogen for transportation and its fishing fleet. Australia proposed using biofuels for parts of transportation that are hard to electrify. The United States, Denmark, and Europe have set goals to reach 100% renewable energy by 2050, later reduced to 2040. "Zero Carbon Britain 2030" aims to eliminate carbon emissions in Britain by 2030 through renewable energy. In 2015, Hawaii passed a law requiring 100% renewable energy by 2045.

Some confusion exists between renewable energy and the Renewable Portfolio Standard (RPS). For example, if 65 GWh of electricity on the grid comes from fossil fuels and 35 GWh from renewable energy, and rooftop solar produces 80 GWh of renewable energy, the total renewable energy is 115 GWh, and the total electricity on the grid is 100 GWh. In this case, the RPS would be 115%.

Cities like Paris and Strasbourg in France plan to use 100% renewable energy by 2050. In the United States, the National Research Council stated that enough renewable resources exist to help address climate change, energy security, and rising energy costs.

It is estimated that the world will spend an extra $8 trillion over the next 25 years to continue using non-renewable resources. This cost could be avoided by switching to 100% renewable energy. Research in Energy Policy suggests that converting the world to 100% renewable energy by 2050 is possible and affordable, but it requires political support. This would involve building more wind turbines and solar systems, using electric cars, and improving energy transmission and storage. As part of the Paris Agreement, countries update their climate goals, but as of 2018, no G20 country had committed to a 100% renewable energy target.

By 2018, there were 181 peer-reviewed papers on 100% renewable energy. That year, the Special Report on Global Warming of 1.5°C mentioned 100% renewable energy as a way to help limit warming, if findings are confirmed.

As of 2021, wind and solar energy were growing worldwide but still made up only 5% of global primary energy use. A report by J.P. Morgan Asset Management analyzed renewable energy forecasts from eight scientists and research groups between 1970 and 2020. The report claimed the forecasts were overly optimistic because they ignored challenges like energy density, unpredictable supply, and the complexity of existing energy systems.

Places with near 100% renewable electricity

The following places meet 90% or more of their average yearly electricity demand with renewable energy (incomplete list):

• Albania: Hydroelectric power
• American Samoa Tau: About 100% solar power, with battery backup
• Australia Tasmania: Hydropower supplies 100% of Tasmania’s electricity. (Plans to reach 200% renewable power by 2040, with the extra energy sent to mainland Australia via underwater power cables)
• Austria Lower Austria: 63% hydroelectricity, 26% wind, 9% biomass, 2% solar
• Bhutan: Mostly hydroelectricity; exports 70% of its production due to excess energy generated; no fossil fuel power plants
• Canada British Columbia: 97% hydroelectric Manitoba: 97% hydroelectricity, 3% wind, less than 1% petroleum (diesel in four off-grid communities), less than 1% natural gas Newfoundland and Labrador: 95% hydroelectricity Quebec: 99% renewable electricity is the main energy used in Quebec (41%), followed by oil (38%) and natural gas (10%) Yukon: 94% hydroelectricity
• Costa Rica: 99% renewable electricity. Hydroelectric (90%), geothermal, wind (and others)
• Democratic Republic of the Congo: Almost 100% hydro, but only 9% have access to electricity
• Denmark Samsø: Net greater than 100% wind power and biomass, connected to mainland for balance and backup power
• Ethiopia: Mostly hydroelectricity (>90%). Smaller quantities of wind, solar, and geothermal. 45% of the population has access to electricity as of 2018, and there is a 100% access target set in 2017 for 2025
• Germany Aller-Leine Valley: 63.5% wind, 30% biogas, 10.7% hydro, 3.1% solar Wildpoldsried, Bavaria: 500% wind, solar, hydro
• Greece Tilos: 100% wind and solar power, with battery backup
• Iceland: 72% hydroelectricity, 28% geothermal, wind, and solar power, less than 0.1% combustible fuel (off-grid diesel)
• Norway: 96% hydroelectricity, 2% combustible fuel, 2% geothermal, wind, and solar
• New Zealand South Island: 98.2% hydroelectricity and 1.6% wind. Around one-fifth of generation is exported to the North Island. Tokelau: 93% solar power, with battery backup and 7% coconut biofuel
• Paraguay: Electricity sector in Paraguay is 100% hydroelectricity, about 90% of which is exported, remaining 10% covers domestic demand
• Tajikistan: Hydropower supplies nearly 100% of Tajikistan’s electricity
• United Kingdom Scotland: 97% of electricity (2020) produced from renewables, mainly wind followed by hydroelectric
• United States Kodiak Island, Alaska: 80.9% hydroelectricity, 19.8% wind power, 0.3% diesel generator Palo Alto, California: 50% hydro, rest a combination of solar, wind and biogas Aspen, Colorado: Hydroelectric, wind and solar and geothermal Greensburg, Kansas: 100% – wind balanced with grid connection Georgetown, Texas: 100% – 154MW solar and wind balanced with grid connection Burlington, Vermont: 35.3% hydro, 35.3% wood, 27.9% wind, 1.4% solar photovoltaic Washington Centralia: 90.6% hydro, 7.9% nuclear Chelan County: 100% renewable energy made up of 99.98% hydroelectric and 0.02% wind power. Douglas County: 100% hydro Pend Oreille County: 97.1% hydro Seattle: 86% hydroelectricity, 7% wind, 1% biogas Tacoma: 85% hydro, 6% wind
• Uruguay: 94.5% renewable electricity; wind power (and biomass and solar power) is used to stretch hydroelectricity reserves into the dry season

Some other places have high percentages, for example the electricity sector in Denmark, as of 2014, is 45% wind power, with plans in place to reach 85%. The electricity sector in Canada and the electricity sector in New Zealand have even higher percentages of renewables (mostly hydro), 65% and 75% respectively, and Austria is approaching 70%. As of 2015, the electricity sector in Germany sometimes meets almost 100% of the electricity demand with PV and wind power, and renewable electricity is over 25%. Albania has 94.8% of installed capacity as hydroelectric, 5.2% diesel generator; but Albania imports 39% of its electricity. In 2016, Portugal achieved 100% renewable electricity for four days between 7 and 11 May, partly because efficient energy use had reduced electricity demand. France and Sweden have low carbon intensity, since they predominantly use a mixture of nuclear power and hydroelectricity. In 2018 Scotland met 76% of their demand from renewable sources.

Although electricity is currently around a quarter of world energy supply and consumption; primary energy use is expected to decrease with renewable energy deployment as electricity use increases, as it is likely to be combined with some degree of further electrification. For example, electric cars achieve much better fuel efficiency than fossil fuel cars, and another example is renewable heat such as in the case of Denmark, which is proposing to move to greater use of heat pumps for heating buildings to provide multiple kilowatts of heat per kilowatt of electricity.

100% clean electricity

Other energy sources that produce electricity are considered clean, even if they are not always renewable, because they do not release carbon dioxide or other harmful gases into the air. The biggest of these is nuclear energy, which does not create any emissions. Some people think moving to 100% renewable energy might take too long to help stop climate change, and they believe closing nuclear power plants could be a mistake. Projects that capture and store carbon dioxide can still use coal or natural gas, but they trap the carbon dioxide before it is released into the air. Ways to reduce greenhouse gases may include using these projects along with renewable energy to save money or avoid shutting down existing power plants, which allows for more choices in creating an electricity system with no carbon emissions.

In 2018, California passed a law called SB 100, which requires 100% clean, carbon-free electricity by 2045, including 60% from renewable sources by 2030. In 2019, Washington passed a law requiring 100% clean electricity by 2045 and banning coal by 2025. Other states and territories that have set goals for 100% carbon-free electricity include Hawaii, Maine, Minnesota, Nevada, New Mexico, New York, Virginia, Puerto Rico, and Washington, DC. A study by Global Energy Monitor shows that China is expected to produce 1,200 gigawatts of renewable energy (from wind and solar) by 2025.

Obstacles

According to Mark Z. Jacobson, the biggest challenges to using large-scale renewable energy and low-carbon energy systems quickly enough to stop dangerous climate change are mainly political, not technological. A 2013 report called Post Carbon Pathways reviewed many international studies and found that the main obstacles include:

In 2011, the Intergovernmental Panel on Climate Change (IPCC), a group of top climate scientists chosen by the United Nations, said that as energy systems grow, there are few or no basic technology limits to using a mix of renewable energy sources to meet most of the world’s energy needs in places where renewable resources are available. The IPCC also said that renewable energy use is expected to increase globally. If governments support renewable energy and all available technologies are used, renewable energy could provide nearly 80% of the world’s energy use in 40 years. Rajendra Pachauri, the IPCC chairman, said that investing in renewable energy would cost about 1% of the world’s total economic value each year. This could keep greenhouse gas levels below 450 parts per million, a level scientists say is safe to avoid dangerous, long-lasting climate change.

Stephen W. Pacala and Robert H. Socolow created a plan called "climate stabilization wedges" to help societies reduce emissions while keeping their quality of life. Renewable energy sources are the largest part of their plan.

Lester R. Brown, founder of the Earth Policy Institute, a research group in Washington, D.C., says switching to 100% renewable energy is both possible and necessary. He compared this effort to the United States’ rapid industrial and economic changes during World War II, saying a similar urgent approach is needed to protect civilization.

According to the World Bank, a climate plan that keeps global warming below 2°C would need 3 billion tons of metals and minerals by 2050. Supplies of some materials, like zinc, molybdenum, silver, nickel, and copper, would need to increase by up to 500%. A 2018 study looked at the materials needed to change the global energy system by 2060. Current battery technologies and known reserves of cobalt and lithium are not enough for this plan. Batteries that use less or no cobalt are possible, but replacing lithium with other materials while keeping performance and cost is harder.

Some large organizations resist plans for 100% renewable energy, believing the world cannot do without fossil fuels or nuclear energy. Groups like the International Energy Agency and the IPCC have been criticized for not including studies on 100% renewable energy in their reports.

A report said China is expected to produce nearly 95% of the world’s polysilicon and other parts of solar panels. This high level of control over a global supply chain could create risks.

A major challenge for 100% renewable energy is the unpredictability of energy sources like wind and solar, which sometimes cannot produce enough power ("Dunkelflauten").

Solutions to manage this unpredictability include:
– Using flexible energy sources like biomass (pellets, woodchips, algae, or crops from former meat-producing land) or hydroelectricity
– Diversifying renewable energy sources
– Building large power grids that connect different regions with unique resources
– Storing excess energy or converting it into other forms, like green hydrogen
– Using geothermal energy to reduce storage needs or provide reliable power
– Building more solar and wind power than needed
– Using smart grids to adjust energy use and demand
– Using vehicle batteries to supply energy to the grid when needed
– Scheduling noncritical energy use during off-peak hours
– Improving how electricity, heat, transport, and industry interact
– Using energy storage technologies like batteries, thermal storage, and ammonia

In 2013, Vladimir Smil studied plans to rely on wind and solar power, including those by Jacobson and others. He pointed out problems like cost, energy supply unpredictability, growing opposition from nearby communities, and a lack of infrastructure. He said the challenges are greater than some experts believe. Smil and Hansen are concerned about the changing output of solar and wind power. Amory Lovins said the electricity grid can handle this unpredictability, just as it backs up failing coal or nuclear plants with working ones.

In 2014, the IPCC said that missing any one technology, like bioenergy, carbon capture, nuclear, wind, or solar, could greatly increase the cost of reducing climate change. For example, without carbon capture, reducing emissions could cost 40% more. A 2018 study said that without reliable low-carbon energy sources (like nuclear or geothermal), the cost of switching to clean energy would rise sharply. Energy prices could be 42-163% higher in regions with less renewable energy availability, and 11-105% higher in regions with more. The study introduced the term "firm low-carbon energy source," which works with fast-response sources (like batteries) and energy-saving renewable sources.

The International Energy Agency said too much attention has been given to the problem of renewable energy supply changes. This issue mainly affects wind and solar power and depends on factors like how much renewable energy is used, how the system is connected, and how flexible energy demand is. Variability is rarely a problem when reliable energy sources like hydroelectricity are also available. However, at high levels of renewable energy use, careful planning and extra costs may be needed. Renewable energy use between 20-50% of total energy has already been achieved in some areas.

Recent developments

The Fourth Revolution: Energy is a German documentary film released in 2010. It describes a vision of a global society that uses 100% renewable energy to power the world. The film shows how the economy would need to change to achieve this goal. In 2011, Hermann Scheer wrote a book called The Energy Imperative: 100 Percent Renewable Now, published by Routledge.

Reinventing Fire is a book by Amory Lovins, released in October 2011. Lovins argues that using less energy and improving energy efficiency could save $5 trillion and grow the economy faster. He believes this can be achieved by using existing energy-saving technologies in the marketplace, led by businesses. Former U.S. president Bill Clinton called the book a "wise, detailed and comprehensive blueprint." The first paragraph of the book's preface states:

The Intergovernmental Panel on Climate Change has said that there are few major technological limits to using renewable energy technologies to meet most of the world's energy needs. A 2011 review of 164 recent studies on renewable energy growth found that most expected renewable energy to supply more than 17% of total energy by 2030 and 27% by 2050. The highest forecast predicted 43% from renewables by 2030 and 77% by 2050.

In 2011, the International Energy Agency stated that solar energy, in many forms, could help solve urgent global problems.

In 2011, the peer-reviewed journal Energy Policy published two articles by Mark Z. Jacobson, a Stanford University engineering professor, and Mark A. Delucchi, a research scientist. The articles discussed how wind, water, and solar power could supply all the world's energy for electricity, transportation, and heating/cooling. The authors analyzed the feasibility of this system. In Part I, they described the characteristics of a wind, water, and solar (WWS) energy system, energy demand, resource availability, and the number of devices needed. They estimated that 3,800,000 5 MW wind turbines, 5,350 100 MW geothermal power plants, and 270 new 1300 MW hydroelectric power plants would be required. For solar power, 49,000 300 MW concentrating solar plants, 40,000 300 MW solar photovoltaic power plants, and 1.7 billion 3 kW rooftop photovoltaic systems would also be needed. This WWS system could reduce global power demand by 30%. In Part II, Jacobson and Delucchi discussed challenges like energy supply variability, system costs, and energy policies. They suggested producing all new energy with WWS by 2030 and replacing existing energy systems by 2050. They said the main barriers to this plan are social and political, not technological or economic. They also said energy costs with a WWS system would be similar to current costs.

Jacobson has said that wind, water, and solar technologies can supply 100% of the world's energy, eliminating all fossil fuels. He supports using a mix of renewable energy sources to reliably meet electricity needs.

A 2012 study by the University of Delaware for a 72 GW system analyzed 28 billion combinations of renewable energy and storage. It found that the most cost-effective plan for the PJM Interconnection would use 17 GW of solar, 68 GW of offshore wind, and 115 GW of onshore wind. At times, this system would provide up to three times the energy needed. Only 0.1% of the time would energy from other sources be required.

In March 2012, Denmark's parliament approved new programs to promote energy efficiency and renewable energy. These programs aim to produce 100% of electricity, heat, and fuels from renewables by 2050. IRENEC is an annual conference on 100% renewable energy started in 2011 by Eurosolar Turkey. The 2013 conference was held in Istanbul.

Jacobson and his colleagues have created detailed plans for switching to 100% renewable energy in New York, California, and Washington states by 2050. By 2014, a plan for all 50 U.S. states was developed, including an online map showing renewable energy potential in each state. This plan is part of The Solutions Project, led by Jacobson, actor Mark Ruffalo, and filmmaker Josh Fox.

By 2014, many studies showed that energy needs for a world with higher living standards could be met economically using wind, solar, biomass, biofuel, hydroelectric, oceanic, and geothermal energy. While detailed plans are still debated, switching to renewable energy is considered technically possible, economically viable, and socially acceptable. This idea supports Germany's goal, called Energiewende, to transition to renewable energy.

In 2015, a study published in Energy and Environmental Science described a path to 100% renewable energy in the U.S. by 2050 without using biomass. The study said this plan is environmentally and economically feasible. It would save about $600 billion annually in health costs from reduced air pollution and $3.3 trillion in global warming costs. This would save about $8,300 per person each year compared to current energy practices. The study noted that the main barriers to this plan are social and political, not technical or economic, because many people are unaware of the benefits.

In June 2017, 21 researchers published an article in Proceedings of the National Academy of Sciences criticizing Jacobson's earlier work. They said he used incorrect models and made unrealistic assumptions, such as increasing energy storage from 43 minutes to 7 weeks and expanding hydropower by the equivalent of