King Coal has been kicked off the throne.

Natural gas is now the nation’s leading source of electricity. It is abundant and cheap, which has not only crippled the coal industry but has also affected virtually every other source of power that makes up the energy grid.

Some have estimated that the United States has enough natural gas to meet the country’s energy needs for about 200 years.

But “King Gas” has its critics — especially among environmentalists — and California’s fast-changing energy landscape offers hints that a long, smooth reign for natural gas is far from assured.

The gas revolution

As late as 1986, natural gas was used to generate just 10 percent of the country’s power. By 2016, that figure leaped to 34 percent, supplanting coal as the No. 1 source of electricity. The U.S. Energy Information Administration recently projected the nation’s use of electricity from gas will exceed coal by 6 percent by next year.

What changed?

Producers have been able to unlock vast amounts of natural gas through the combination of hydraulic fracturing, also known as fracking, and horizontal drilling techniques in shale formations such as the Barnett in Texas and the Marcellus Shale in Pennsylvania and parts of Ohio and West Virginia.

Just a few years ago, the U.S. had to import natural gas from other countries to meet its needs. Today, there is so much that U.S. producers export natural gas to places like Mexico.

Burgeoning supplies caused the price of natural gas to drop. At some periods between 2003 and 2008, the price approached $14 per million British thermal units, a common industry measurement. Since the fracking boom, prices averaged less than $3.20 per million BTU.

Those low prices are one reason that natural gas is attractive to utilities as a way to generate electricity. Natural gas-fired plants also have the ability to “ramp up” power very quickly.

In addition, natural gas burns twice as cleanly as coal.

“The biggest, most disruptive innovation in the energy sector in the last 30 years is unconventional natural gas” from shale formations, said Frank Wolak, professor of economics and an energy expert at Stanford University. “There is no doubt that if that innovation had not occurred, we would be burning even more coal.”

A ripple effect

Even major oil companies are focusing more on natural gas. For example, of the 16 new projects BP plans to complete by 2021, 12 of them involve natural gas instead of oil.

Diesel is also feeling the impact. Increasingly, city governments are switching their fleets of metropolitan vehicles, such as buses, from diesel to natural gas.

Low natural gas prices have delivered a body blow to nuclear power, eating into revenue. An analysis by Bloomberg New Energy Finance found more than half of U.S. reactors are losing money.

California’s last nuclear reactor in operation, Diablo Canyon, is slated to begin closing its doors in 2024.

It appears nuclear’s losses equal gains for natural gas.

When the San Onofre Nuclear Generating Station closed permanently after a January 2012 leak, natural gas as a percentage of California’s in-state generation ballooned from 45.4 percent in 2011 to 61.1 percent in 2012, according to figures from the California Energy Commission.

Role of renewables

Falling prices for renewable energy sources, such as solar and wind, plus aggressive mandates from state policymakers have propelled California to the forefront of integrating renewables into the state’s power mix.

In the energy commission’s most recent figures, the share of in-state generation from renewables reached 27.9 percent in 2016 — nearly twice as much as in 2009.

At the same time, growth in wind and solar is often linked to growth in natural gas.

That’s because wind and solar have problems with intermittency: Solar production slips when the sun doesn’t shine and electricity generated by wind wanes when breezes don’t blow. Supplies of natural gas smooth out the gaps.

Mark Zoback, director of the Natural Gas Initiative at Stanford University, said the relationship between renewables and natural gas is not an either/or proposition.

“If the sun is really shining, which is mostly in the afternoon, or the wind is really blowing, which is mostly at night, you can cycle the natural gas plants to compensate for what the renewables are or are not doing,” he said.

Zoback said the long-term future of energy will belong to renewable sources, but they’re not there yet and abundant supplies of natural gas will help foster the transition.

The opposition

Environmental groups are uniformly opposed to natural gas.

Although cleaner than coal, natural gas is nonetheless a fossil fuel that emits greenhouse gases. Natural gas is mostly made up of methane, and there are concerns about leaks because methane, if released into the atmosphere, is about 30 times more potent than CO2.

“When you take into account the environmental impacts and the dangers of climate change associated with natural gas, it might be natural, but it’s not good for the environment,” said Dan Jacobson, state director at Environment California.

In California, there’s a growing school of thought that there is too much natural gas in the system.

A Los Angeles Times investigation last year reported a growing glut of power in the state. California power plants, based on estimates, were on track to produce at least 21 percent more electricity than needed by 2020.

“We’ve been building up our gas-fire infrastructure at a rate that we could turn off every solar panel and every wind turbine right now and we wouldn’t skip a beat,” said Bill Powers, an engineer and consumer advocate based in San Diego.

The future

Powers said natural gas dominance is no sure thing, pointing to falling prices for alternative energy sources.

“If in a few years you can produce power at $25 a megawatt-hour from a solar field or buy it at a gas plant at $35, just on cost alone a lot of solar is going to be built, even in states where there’s no green mandate and no pressure to go green,” Powers said.

Zoback, of Stanford’s Natural Gas Initiative, isn’t so sure natural gas will lose its grip that quickly.

“My sense is that we’re going to see expanded use of natural gas for the next 20 years,” Zoback said. “In the following 20, it will have a useful decline; and 40 to 50 years from now, I think we will be using very little natural gas. We’ll largely have renewable sources.”