In 2000, wind and solar combined to be the source of just 0.1% of all electricity generated in the United States. No wonder renewable energy had so many critics. To be fair, wind and solar were expensive, inefficient, and hadn't done much of anything since being hyped up during the energy crisis in the 1970s. But all of that has changed now. 

Today, wind power is, on average, the cheapest source of electricity on a levelized cost basis in the United States. Solar power is third, just behind natural gas, and together with wind, the renewable pair is responsible for nearly 10% of total electricity production in the country. Shares of companies that have led installments, such as NextEra Energy (NYSE:NEE) and Xcel Energy (NASDAQ:XEL), have thumped the S&P 500 in the last two decades or so as a result.

Investors probably haven't missed out yet. Considering that wind and solar could provide 25% or more of America's electricity by 2030, and new opportunities are emerging in offshore wind and a next-generation geothermal technology, there could be decades of growth left in renewable energy stocks. Here are five amazing facts about how we got here, and where we might be heading.

Wind turbines along a country road.

Image source: Getty Images.

1. American wind power has grown 4,810% since 2000

The United States is on pace to generate 275 terawatt-hours of electricity from onshore wind power in 2018, compared to just 5.6 terawatt-hours in 2000. That amounts to a whopping 4,810% increase since the turn of the century. By comparison, the S&P 500 has gained 168% in that span with dividends (and two brutal recessions) included. 

Therefore, it shouldn't be surprising that some of the best-performing stocks in that span belong to businesses that went all-in on the future of wind power. NextEra Energy stock has delivered a total return (share performance plus dividends) of 1,430% in that time, growing from a ho-hum electric utility in Florida to the world's largest publicly traded utility. Even shares of Xcel Energy, which only began investing heavily in renewable energy in the last decade, have put up a total return of 477% in that period.

NextEra Energy and Xcel Energy began the year with nearly 21,000 megawatts of installed wind capacity combined, or about one-quarter of the country's total. The companies have played a pivotal role in increasing wind power's share of nationwide electricity generation to nearly 7% -- enough to make it the nation's top renewable energy source, something hydropower has claimed for over 100 years -- and hope to replicate their success with solar power. While solar electricity production is about 10 years behind the trajectory of wind power, it could grow more quickly as costs continue to decline.

A jar of coins overflowing.

Image source: Getty Images.

2. One company's renewable energy backlog will hit 40,000 megawatts

The United States exited 2017 with an estimated 115,000 megawatts of installed wind and utility-scale solar power capacity. It took decades, dozens of industry players, and tens of billions of dollars for the country to reach that level. If NextEra Energy has its way, then the next 115,000 megawatts might take significantly less effort. 

The company's power-generation subsidiary, NextEra Energy Resources, has plans to grow its renewable energy project backlog to 40,000 megawatts by 2020. Perhaps equally impressive is the fact that each major region of the United States is represented in the ambitious portfolio, even those considered to have relatively poor renewable energy potential, whereas today, most wind and solar energy power capacity is concentrated in only a handful of states. Considering the business' current backlog is larger than its entire operating portfolio at the end of 2011, investors don't have to guess at the appetite for wind and solar projects among American electric utilities. 

A satellite hovering over North America.

Image source: Getty Images.

3. American ethanol helps create the biggest carbon sink on the planet

When low-orbit satellites survey planet Earth for regions with the most photosynthetic activity, a measure of plant growth and carbon dioxide consumption, jungles and the occasional algal bloom in the ocean stand out as expected. But no region swipes more carbon dioxide out of the atmosphere than the American Midwest, home to America's Corn Belt. 

In addition to being a prolific carbon sink, the American Corn Belt is home to over 90% of the country's ethanol production and more than half of total global output. That has created problems in recent years for producers such as Archer Daniels Midland and Green Plains (NASDAQ:GPRE), which are drowning in oversupply, but the industry is taking a lesson from the country's oil and gas boom with hopes to create a more sustainable future: exporting the excess. 

The United States is on track to export 1.8 billion gallons of ethanol in 2018, and it has now exported over 1 billion gallons for three consecutive years. Considering more export terminals are coming online this year and next, and nearly 1 billion gallons of ethanol production capacity remains offline, this is a trend that shows no signs of slowing

Offshore wind turbines.

Image source: Getty Images.

4. Offshore wind capacity could grow to 23,375 megawatts by 2030

The United States will soon have 100,000 megawatts of onshore wind power in operation, but the technology's offshore counterpart hasn't even been able to launch from the starting block. Hindered by a lack of domestic expertise, high costs, and zoning issues, offshore wind power boasts just 30 megawatts of installed capacity in the country today. That's all about to change thanks to a helping hand from Europe.

After cutting their teeth on their home continent, which hosts the overwhelming majority of offshore wind projects on the planet, European players such as Orsted are crossing the Atlantic to grab a piece of North America's incredible untapped potential. The United States could realistically generate more than twice its total electricity needs from offshore wind power in the Lower 48. Tremendous power potential, falling costs, and experience gleaned from Europe have resulted in a project pipeline of 23,375 megawatts today. Most of that could come online by 2030 and greatly improve the carbon footprint of American cities, most of which are located on or near an oceanic coast or one of the Great Lakes.

The inside of a cooling tower.

Image source: Getty Images.

5. Geothermal energy could replace nuclear power, with help from fracking

Nuclear power is currently the nation's largest source of carbon-free power, comprising roughly 19% of the country's total electricity consumption. But it's in trouble. Atomic energy facilities simply can't compete economically with lower-priced natural gas and wind power. While some states have provided subsidies to reward nuclear power plants for providing carbon-free electricity, that can't continue indefinitely. By 2030, the country's aging fleet will be long overdue for retirement.

Help could come from a completely unexpected source: geothermal energy. The U.S. Department of Energy is quietly funding the development of a novel technology called enhanced geothermal systems (EGS). By using fracking technology pioneered and perfected for use in shale oil and gas regions, it may be possible to create geothermal energy wells across the United States that can produce massive amounts of clean energy.

In what can only be proof that we are indeed living in a simulation, the numbers are almost too good to be true. The United States has an estimated 100,000 megawatts of easily accessible next-generation geothermal potential -- exactly the amount of nuclear power currently operating. Geothermal is the second most efficient energy source by a mile, right behind nuclear power, and the U.S. DOE is targeting a deployment date of 2030 -- exactly when the nation will need to replace its nuclear fleet.

The opportunity isn't quite ready for individual investors yet, but companies that specialize in oil and gas well optimization such as Core Laboratories and Ecolab can also tap into emerging opportunities in EGS. In fact, Core Laboratories has a dedicated EGS business today.

Maxx Chatsko has no position in any of the stocks mentioned. The Motley Fool recommends Core Laboratories and Ecolab. The Motley Fool has a disclosure policy.