Top 5 Commercial Renewable Energy Sources

Photo illustration with solar panels and wind turbines

Renewable Energy is Good for Business

2020 has undoubtedly been a year of firsts. But did you know that it also marked a year of unprecedented successes in the clean energy industry?

For the first time, renewable energy generation not only outpaced coal-fired energy production but also firmly placed itself as the cheapest, at-scale, proven energy option available.

Corporate and Environmental, Social and Governance (ESG) investment funds spurred much of that growth. Proving that renewable energy is good for business, corporate power purchase agreements (PPAs) surged while public corporate commitments, such as the RE100, to switch to 100% renewables also outpaced the market.

What makes an energy source renewable and why are they so popular?

What is Renewable Energy?

Open wind turbine pod bay

There are two key factors that make energy renewable. First, it is generated from natural resources that readily replenish. Second, renewable energy also creates few to no greenhouse gas emissions (GHGs).

Many people think of renewable energy as something new. In reality, the power available through natural resources is something humanity has relied on since learning how to cook on a wood fire, sail to new places through the power of wind, or power the first factories with water wheels.

Renewable Energy is the Cheapest Energy Option

Money talks. And the word is out that by leveraging a variety of sources, renewable energy is often the cheapest energy option – even without government subsidies.

The International Renewable Energy Agency (IRENA) released a report in May 2020 showing that the cost for utility-scale solar photovoltaic – the most widely deployed, versatile, and cost-effective solar panel technology on the market today – or solar PV power declined 82% since 2010. During the same time period, the costs for onshore and offshore wind declined by 39% and 29% respectively.

So decarbonization of the power sector is not only doable, it's affordable – which explains why renewable energy is replacing fossil fuels. According to the U.S. Energy Administration, renewables made up more than 17% of the U.S. energy mix in 2019 – nearly twice the 9% share in 2000. Conservative projections are that we can exceed 30% in the next 10 years, by 2030.

The top 5 commercial renewable energy sources, as ranked by market share and growth, are:
  1. Wind
  2. Hydropower
  3. Solar
  4. Geothermal
  5. Emerging & Emissions Boosters

#1: Wind Energy

Aerial view of a wind turbine farm in Western US

"As yet, the wind is an untamed and unharnessed force; and quite possibly one of the greatest discoveries hereafter to be made will be the taming and harnessing of it."
— Abraham Lincoln


In its 2019 Wind Powers America Report, the American Wind Energy Association identifies wind as America's top renewable, no-emissions energy source.

Wind energy provides 7% percent of all U.S. electricity with nearly 60,000 large-scale wind turbines operating across 41 states and two territories – check out the wind map of the U.S. to see where electricity is generated near you. Wind energy includes electricity generated from onshore sites (such as 350-MW Frontier II in Oklahoma and 182-MW Maryneal in Texas), massive offshore towers, and smaller turbines located on and between commercial properties. In 2020, the Energy Information Administration predicts that wind will become the No. 1 generation source, comprising 44% of all new electric generating capacity.

It's not surprising that wind generation ranks as No. 1 considering humanity's use of wind as energy dates back as far as the first sailing ships, sometime between 3000 to 1500 B.C. Operating for over 1,000 years, the windmills of Nashtifan, Iran, are among the oldest in the world, and have withstood winds of up to 74 miles an hour. Whether used as power for transportation or converted into mechanical energy for pumping water, grinding grain or powering steam engines, wind energy is clean, abundant, and available around the world.

What's next for wind? Through major advancements in onshore performance and creation of massive offshore wind towers, the largest turbine is currently over 722 feet tall and individually generates 9.5 MW of electricity. Future turbines may be even taller, airborne, and include military-grade kites to microgenerators that work in low-wind environments and even bladeless turbines.

#2: Hydropower

Aerial view of a hydroelectric dam

"Water is to me, I confess, a phenomenon which continually awakens new feelings of wonder as often as I view it."
— Michael Faraday, 1853 Inventor of the first electric generator.


Number 2 (previously number 1 until wind surpassed it in 2020) is that giver of life: water and its energy generation alternative, hydropower. According to the National Hydropower Association, energy produced by moving waters – rivers, streams, and ocean tides – accounted for 7% of total electricity generation.

Hydropower is one of the oldest power sources on the planet. Farmers of ancient Greece used moving water to spin turbines and complete tasks like grinding grain. During the U.S. industrial revolution, hydropower provided the mechanical energy necessary to produce textiles and other equipment. And in 1882, the first U.S. hydroelectric power plant was constructed in Appleton, Wis., powering lighting for a paper mill and multiple homes. One of the country's largest commercial energy holding companies, Duke Energy (parent company of Duke Energy Renewables), began its operations as a hydroelectric company in 1900. The company continues to own and operate 31 hydroelectric and two pumped-hydro storage facilities.

Today, 2,500 dams in 41 states and two territories provide 78 gigawatts (GW) of conventional and 22 GW of pumped-storage hydropower. By comparison, there are more than 80,000 dams nationwide that do not produce electricity. While not all of these dams are suitable for power production, a U.S. Department of Energy study suggests that adding power generating capacity to just 100 of these dams could potentially add up to 8 GW of new renewable capacity – enough power to energize about 3.2 million homes and increase the size of the existing conventional hydropower fleet by 10%.

Like any energy generation source created by humans, hydropower has good and bad sides. The well-known negative impact on fish and natural ecosystems is causing many older dams to be demolished. One advancement is the potential to combine hydropower as energy storage to work in conjunction with solar when the sun is not shining and/or wind when the air is still. Hybrid renewable energy generation is discussed more in number 5 of our list.

#3: Solar

Solar panels in the midday sun

"I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that. I wish I had more years left!"
— Thomas Edison


The sun is another natural source of energy, emitting enough energy each second to satisfy the global energy demand for over two hours. So it's not surprising that solar energy generation, such as solar PV, is one of the fastest growing commercial renewable energy resources.

Solar generation works anywhere the sun shines with eight U.S. states already generating over 5% of their electricity from solar. California leads the way at around 19% and in North Carolina, where Duke Energy Renewables is headquartered, 6% of the energy is sourced through solar. The U.S. solar market is expected to hit 3 million installations in 2021 and 4 million installations in 2023.

Tapping the sun for power has an ancient history, dating back as far as 7 B.C. when humans first used it to light fires. The first silicon PV and solar cells capable of converting enough of the sun's energy into power to run everyday electrical equipment were developed in 1954 by Daryl Chapin, Calvin Fuller, and Gerald Pearson in Bell Labs. The world's longest operating solar plant, Solar Energy Generating Systems (SEGS), began generating commercial-scale solar in the 1980s from the Mojave Desert.

Today, solar generation ranges from ultra-lightweight and portable solar chargers suitable for backpacking to large-scale solar operations like Amazon's largest solar rooftop in Colorado, and from solar at universities and schools to utility-scale projects like the 200-MW Holstein Solar project in Texas. Researchers estimate that with all of the advancements in solar technologies, we could achieve 700% energy production improvement by 2050 (or sooner).

#4 Geothermal

Steam emitting from a geothermal vent

"In the old economy, energy was produced by burning something ... The new energy economy harnesses the energy in wind, the energy coming from the sun, and heat from within the earth itself."
— Lester R. Brown


Geothermal energy (the heat from Earth) is number 4 on our list of top commercial renewable energy sources. Hot water exists naturally at varying temperatures and depths below the Earth's surface. Very deep wells of a mile or more can be drilled into these underground reservoirs to tap and bring the steam to the surface for use in a variety of applications, including electricity generation, heating and cooling, and other direct uses. In the U.S., most geothermal reservoirs are located in the western states. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in Northern California that also uses reclaimed wastewater as an added water source.

The first geothermal power plant located in Tuscany, Italy, began operating in 1904. It generated a mere 10 kilowatts of electricity, enough to power five lightbulbs. A major advantage of geothermal power is that it requires no fuel, making it immune to fluctuations in fuel cost. However, capital costs – primarily the cost of drilling – tend to be high. There is also high financial risk associated with locating viable geothermal resources.

The future of geothermal may be in its byproducts – specifically, the valuable mineral lithium. Lithium is a critical component of large-scale battery technologies used in battery energy storage systems and electric vehicles. To create new sources for the sought-after mineral, the state of California is financing a lithium extraction project to create a profitable, emissions-free byproduct from existing geothermal energy generation.

#5 Emerging Renewables & Emissions Reducers

Battery storage arrays

"If you want to find the secrets of the universe, think in terms of energy, frequency and vibration."
— Nikola Tesla


Number 5 on our list includes emerging renewable energy technologies as well as innovations that, by themselves, do not strictly generate energy. Instead, they augment other renewable energy resources. The "boosters," as we'll call them, are all about overcoming the intermittency of renewables like wind and solar and lower costs as well as emissions.

Renewable Energy boosters include:

  • Energy Storage – By capturing energy produced at one time and storing it for use at another, energy storage is seen as a critical means to assure new energy sources are not wasted (e.g., curtailment of wind and solar when there is too much energy on the grid) and are available when sources are not producing (e.g., at night when solar panels are not capturing energy from the sun). Battery energy storage systems (BESS) are by far the fastest growing and most widely deployed energy storage, adding energy resiliency and significant cost savings when paired with solar and wind projects. Example: the 36-MW Notrees Battery Storage Project, America's largest battery storage project at a wind farm. Other energy storage systems are pumped-storage hydropower (PSH) and gravity energy storage, which is a fast-emerging mechanical system you will see plenty more of in the future.
  • Fuel Cells and Green Hydrogen – Fuel cells work like batteries, but they do not run down or need recharging. They produce electricity and heat as long as fuel is supplied. Today, that fuel is typically hydrogen made by the process of electrolysis of water using fossil fuels. To achieve no-emissions, a variant fuel source called "green hydrogen" is created by the same electrolysis process, but it is fueled by no-emissions wind and/or solar. Fuel cells are used to deliver on-site, baseload power.
  • Energy Efficiency – As buildings, vehicles, and devices all become more efficient, less energy is used or needed to be produced. The less energy used, the less generation is needed. Assuring high levels of energy efficiency will lower the need for every energy generation source.
  • Electrification – This is the conversion of a machine or system to electrical power. From building heating and cooling to cars, buses, trucks, ships and aircraft, electrification shifts energy needs to cleaner energy sources and helps to achieve net-zero emissions faster. Many point to the future of energy being the decarbonization and electrification of vehicles. That means everything from e-bikes to huge, 45-ton dump and mining trucks that are as big as a three-story office building.

Emerging renewable energy technologies to watch include:

  • Tidal Energy – A renewable source of power drawn from the ebb and flow of the oceans. In its simplest form, turbines beneath the ocean's surface rotate as the tides rise and fall to produce electricity that is then fed back to the shoreline via underwater cables. Tidal energy is also produced through large structures built across a river, usually near its mouth where it meets the ocean, called barrages. As we have not yet cracked how to limit negative impacts on sensitive ocean and beach ecosystems, and costs remain high, the U.S. does not have any utility-scale tidal power generating plants. But success in Asia and interest in combining with desalination plants to create drinkable freshwater from seawater may change that in the not-so-distant future.
  • Biogas – Biogas is produced by anaerobic bacterial degradation of animal and plant wastes. This differs from biomass/biofuels, which some call renewable because fuels like wood or sugar cane regenerate but were omitted from this list as they currently are considered "high emitting" fuel sources. Bacteria are not picky eaters. These microorganisms devour agricultural waste, manure, municipal, sewage, green waste, or food waste. The resulting biogas is methane, also called natural gas, which is then combusted or burned to generate electricity. An example is Duke Energy working with dairies in its service territories to pipe methane from manure through its natural gas pipelines to generation facilities. U.S. staples like Connecticut are also placing significant time and investment to combine solar, wind and biogas at trash dumps and other "brownfield" sites to provide a consistent source of energy generation.
  • Radiant Energy – As energy transmitted in wave motion, especially electromagnetic wave motion (e.g., magnets plus motion), this natural energy form can be gathered directly from the environment or extracted from ordinary electricity by the method called fractionation. One of the earliest wireless telephones to be based on radiant energy was invented by Nikola Tesla back in 1916. Today, 99% of the cost of normal electricity can be saved by the use of radiant energy. There are a number of pilots of self-running devices that tap radiant energy. No power plant required. The ultimate renewable energy is that which happens in the device itself. Stay tuned!
  • Future Renewables – In labs around the world, there are many innovations being explored. Some, like Fuel from Air and exponential improvements in solar cell capacities, look extremely promising. It remains to be seen which future renewable energy sources achieve the scale, safety, and reliability needed to power a world of electricity needs.

Which renewable energy source is best for you?

Even in uncertain times, the demand for clean energy continues to grow. The truly great news is that over the past decade, renewable energy innovation has stepped out of the "alternative energy" category and into the mainstream by being very affordable, increasingly reliable, and generally available to a wide audience. It will be fun to compare lists in 2030 to what the top renewable energy sources are in 2020. We look forward to doing an update for you then!

About Duke Energy Renewables

Learning the basics of renewable energy, including major types of renewable energy is step one in developing sustainable energy solutions for your business. Getting that information from a trusted source with a track record in providing renewable energy services and solutions is equally important.

We're Duke Energy Renewables and we work with sustainability professionals at major corporations like The Home Depot, Sprint and the Ball Corporation to integrate sustainable solutions into their operations to produce energy savings and target carbon reduction goals. We're experts in guiding you to energy savings, energy independence and we're here to help.