chevron-down Created with Sketch Beta.
April 21, 2021 Feature

Moving Toward a Zero-Carbon Energy Sector: The Potential Negative Effects of Removing Natural Gas from the Generation Mix

By Eric B. Gallon and Daniel R. Conway

The United States has witnessed a historic shift in electricity generation over the last 10 years. Despite the U.S. Supreme Court’s stay of the Clean Power Plan, President Barack Obama’s signature plan to reduce greenhouse gas emissions from existing electric generating units, and President Obama’s replacement in the White House by the coal-friendly President Donald Trump, coal-fired generation in the United States is dwindling. In its place, natural gas–fired generation has become the primary source of electric power in the country, and renewable generation has increased significantly.

However, several large and small states are now pushing to transition away from natural gas–fired generation and toward a zero-carbon energy sector—a goal that President Joe Biden’s administration has also now set. If not handled with caution, this next transition may threaten the adequacy and reliability of the electrical grid and the affordability of energy for consumers.

This article explores the changes in generation that have brought the United States to its current position, the state and federal goals for reducing greenhouse gas emissions from the energy sector, and the potential effects of the transition toward zero-carbon energy.

Trends in Natural Gas–Fired Generation under the Last Two Administrations

The Obama Administration

At the end of President Obama’s first term in office and the beginning of his second term, the president and his administration were bullish on natural gas. At his speech to the Democratic National Convention in late 2012, President Obama asserted that his reelection would lead to “a future . . . where we develop a hundred-year supply of natural gas that’s right beneath our feet.”1 And the next year, after he won reelection, he released his Climate Action Plan, which celebrated America becoming “the world’s leading producer of natural gas” and noted that “natural gas [had] increas[ed] its share of electricity generation in recent years.”2

In 2013, President Obama directed the Environmental Protection Agency (EPA) to regulate carbon pollution from power plants and touted “efficient natural gas” as one of the “cleaner energy technologies” the United States could rely upon to “reduc[e] power plant pollution.”3 And like President Obama, many environmental organizations supported natural gas–fired generation as a means to reduce greenhouse gas emissions. Clean Air Task Force, for example, encouraged President Obama to set emission standards for new power plants “at the emissions rate typical for a new natural gas power plant,”4 which EPA ultimately did for new and reconstructed fossil fuel–fired stationary combustion turbines,5 and to set standards for existing power plants “by curtailing the operation of older inefficient coal plants, in favor of cleaner plants, like underutilized existing natural gas plants,” which EPA also ultimately did.6

Despite its support for natural gas–fired generation, however, the Obama Administration saw natural gas as only a “‘bridge fuel’ . . . as the world transitions to even cleaner sources of energy.”7 Organizations like Clean Air Task Force agreed that “ultimately we will have to wean the planet off fossil fuels and bridge to zero-carbon alternatives.”8 And as early as 2012, environmental organizations that had supported natural gas–fired generation as a cleaner alternative to coal were already feeling pressure to back away from natural gas.9 Sierra Club, for example, launched its rebranded “Beyond Natural Gas” campaign that year, which described natural gas as “dirty” and “dangerous” and asserted the “need to start that transition from natural gas to clean energy yesterday.”10

The Trump Administration

The Obama Administration, as we know, was followed by the Trump Administration. And the Obama Administration’s Clean Power Plan for greenhouse gas emissions from existing power plants never went into effect. The U.S. Supreme Court stayed the Clean Power Plan in early 2016.11 In March 2017, President Trump rescinded President Obama’s Climate Action Plan and several other climate-related executive actions and directed EPA to review and take steps to “suspend, revise, or rescind” the Clean Power Plan “as soon as practicable.”12 Ultimately, the Trump EPA repealed the Clean Power Plan and replaced it with the Affordable Clean Energy rule, a much less aggressive plan that relied only on heat rate improvements to reduce greenhouse gas emissions.13 (The U.S. Court of Appeals for the D.C. Circuit, in turn, vacated the Affordable Clean Energy rule on the final day of the Trump Administration.14)

Yet even President Trump did not disavow cleaner forms of generation. To be sure, President Trump emphasized the importance of “energy independence and economic growth”15 over efforts to address climate change.16 But from the beginning, the Trump Administration endorsed an “all-of-the-above” energy policy,17 declaring that it was “in the national interest to ensure that the Nation’s electricity is affordable, reliable, safe, secure, and clean, and that it can be produced from coal, natural gas, nuclear material, flowing water, and other domestic sources, including renewable sources.”18 In an October 2017 proclamation honoring National Energy Awareness Month, President Trump declared that it was “time we make America’s energy dominance a priority” and “empower Americans to access the vast reserves of coal, oil, and natural gas stored across our land”—but also declared that America should “develop nuclear, hydropower, and all other types of clean and renewable energy.”19

Ultimately, however, the shift from coal-fired generation to natural gas–fired generation and renewable generation that had begun under President Obama continued apace under President Trump. Between 2011 and 2019, 103 coal-fired power plants in the United States “were converted to or replaced by natural gas–fired plants.”20 Natural gas–fired generation in the United States began exceeding coal-fired generation in 201521 and has exceeded all other sources of power in the United States ever since.22 Despite President Trump’s declaration that his administration was “ending the war on coal,”23 coal-fired generation in the United States had fallen to “its lowest level in 42 years” by the end of the Trump Administration.24 And “annual energy consumption from renewable sources exceeded [energy] consumption” from coal for the first time in more than a century.25 As a result, the United States achieved the annual CO2 reductions that the Obama EPA projected under the Clean Power Plan—“32 percent below 2005 levels”26—11 years before the 2030 goal set in that plan.27

The State and Federal Push to End Natural Gas–Fired Generation

The shift to natural gas–fired generation and renewable generation can be attributed to several factors. As explained by the U.S. Energy Information Administration, part of the decrease in the carbon intensity of the U.S. energy sector can be explained by “[i]ncreases in natural gas production from shale . . . that lowered the cost of natural gas production and made it cost competitive with coal for electric power generation.”28 Part of it reflects long-term trends toward increased efficiency, “the changing profile of U.S. manufacturing industries,” and “the shift to greater commercial sector economic activity.”29 But another reason for the decrease in carbon intensity is “[p]olicies that encouraged the use of renewable energy, such as state-level renewable portfolio standards.”30 State renewable portfolio standards (RPSs) were responsible for 60 percent of new renewable energy in the United States from 2008 to 2014, and “just under 30%” in 2018.31

State RPS policies that “require or encourage electricity suppliers to provide their customers with a stated minimum share of electricity from eligible renewable resources”32—are nothing new. Iowa adopted the first state renewable portfolio standard in 1983.33 Now, 30 states, three U.S. territories, and the District of Columbia have RPSs.34 Several of those states have increased their RPS requirements over time.35

And in the last few years, states have begun adopting “clean energy standards,” or goals that require 100 percent renewable or carbon-neutral energy by some date in the next 30 years. Examples include the following.

  • California: California requires that 60 percent of “total retail sales of electricity in California” come from “eligible renewable energy resources” by 2030.36 California law requires the state to “take steps to . . . transition to a zero-carbon electric system” in which “eligible renewable energy resources and zero-carbon resources supply 100 percent of all retail sales of electricity to California end-use customers and . . . state agencies by December 31, 2045.”37
  • Colorado: Retail utilities “providing electric service to more than five hundred thousand customers” in Colorado must “reduce the carbon dioxide emissions associated with [those electricity sales] by eighty percent from 2005 levels” and “provid[e] [their] customers with energy generated from one-hundred-percent clean energy resources” (i.e., “technology that generates or stores electricity without emitting carbon dioxide”) by 2050 “or sooner if practicable, . . . so long as doing so is technically and economically feasible” and “in the public interest.”38
  • Hawaii: Hawaii’s RPS requires that 40 percent of its net electricity sales come from renewable sources by 2030, 70 percent by 2040, and 100 percent by 2045.39
  • Louisiana: In 2018, Louisiana Governor John Bel Edwards issued an executive order creating a Climate Initiatives Task Force and directing it to recommend ways to reduce the state’s net greenhouse gas emission by 40–50 percent (compared to 2005 levels) by 2030 and achieve “net zero” greenhouse gas emissions by 2050.40
  • Maine: Maine law sets “goals for increasing consumption of electricity in the State that comes from renewable resources” such that “80% of retail sales electricity in the State will come from renewable resources” by 2030, and 100% will “come from renewable resources” by 2050.41
  • Nevada: Nevada generally requires providers of electric service “to generate, acquire, or save electricity from portfolio energy systems or efficiency measures in an amount that is . . . 50 percent of the total amount of electricity sold by the provider to its retail customers in this State” by 2030 and thereafter.42 Nevada state law also declares that it is state policy to “achiev[e] by 2050 an amount of energy production from zero carbon dioxide emission resources equal to the total amount of electricity sold by providers of electric service in this State.”43
  • New Mexico: New Mexico’s RPS requires that “renewable energy shall comprise no less than fifty percent of each public utility’s total retail sales of electricity to New Mexico customers” by 2030 and “one hundred percent of all retail sales of electricity in New Mexico” by 2045.44
  • New York: In 2019, New York passed the New York State Climate Leadership and Community Protection Act, which adopts a target of “reducing 100% of the electricity sector’s greenhouse gas emissions by 2040.”45
  • Virginia: As of 2020, Virginia law requires “each Phase I and II Utility” to “retire all . . . electric generating units located in the Commonwealth that emit carbon as a by-product of combusting fuel to generate electricity” by 2045 unless they can demonstrate “that the requirement would threaten the reliability or security of electric service to customers.”46
  • Washington: Washington’s Clean Energy Transformation Act, which became effective in 2019, states that “[i]t is the policy of the state to eliminate coal-fired electricity, [and] transition the state’s electricity supply to one hundred percent carbon-neutral by 2030, and one hundred percent carbon-free by 2045.”47

Washington, D.C., and Puerto Rico have also adopted 100 percent clean energy requirements.48

The Biden-Harris Administration has set an even more aggressive goal than the states listed above, aiming to “achiev[e] [a] 100 percent carbon-pollution-free electric sector by 2035.”49 Although the Biden-Harris Administration has yet to release concrete plans for achieving this goal, their campaign promoted investments in energy efficiency; increased reliance on wind and solar power; “continuing to leverage the carbon-pollution free energy provided by existing sources like nuclear and hydropower”; and investing in new energy technologies, including cost-effective “grid-scale storage” and “advanced nuclear reactors.”50 The campaign’s plan makes no mention of a role for natural gas in the electricity sector.

The Potential Effects of Removing Natural Gas from the Generation Mix

Eliminating natural gas as a fuel option for the electric generation fleet, as several states and the Biden Administration have proposed to do, will have consequences for consumers. They include impacts on the adequacy and reliability of service and on the costs of providing service to end users. Those effects should be taken into account when considering whether, how, or when to remove natural gas from electricity generation.

Adequate and Reliable Service

The provision of services to consumers in adequate quantities and reliably without significant interruptions is a key policy objective. Resilience, the ability to respond to threats and recover from interruption events, may be regarded as a component of reliability. Safely providing adequate and reliable services is closely aligned with policy makers’ fundamental responsibility to promote and protect the health and welfare of the public.

Just and Reasonable Rates

Of course, the provision of electric service, wholesale and retail, at just and reasonable prices is also a fundamental public policy objective. Policy choices that curtail or eliminate the use of natural gas—through restrictions on its use for electricity production and by retail consumers (residential, commercial, and industrial)—will have significant impacts on those objectives.

Energy Efficiency: The Demand Side

An important goal of energy efficiency (EE) programs is to reduce emissions, including carbon emissions, through lower consumption. For example, the less natural gas that is used for space and water heating, cooking, manufacturing, and electricity generation due to more efficient appliances, automated controls (such as smart thermostats), and more efficient combustion technologies, the fewer emissions there will be.

Energy efficiency can be market driven. When policy makers determine that market incentives are not sufficient to encourage adoption of the desired levels of EE improvements, they may provide additional incentives and impose requirements to achieve greater levels of EE. Tax credits, rebates, and other types of subsidy payments to consumers are additional incentives that encourage adoption of additional efficiency improvements. So are shared savings payments to utilities, which incent and reward them for promoting adoption of EE improvements.

Gas and electric utilities, because they are natural monopolies and subject to pervasive regulation, are obvious partners of the policy makers for implementing the extramarket measures used to achieve additional efficiency and lower emissions. They can administer the EE programs and incur the costs of the additional incentives; and they can establish non-bypassable charges to recover the extramarket costs of those additional EE incentives. Then, the collection of those incentive costs can be spread over the utilities’ entire customer bases, and the per-customer cost impacts of the additional incentives can be mitigated, even in cases when the cost-saving benefits of the EE programs primarily flow only to those who participate.

Utilities can also be required to achieve prescribed levels of reduced retail consumption, for example, in comparison to historical baseline measures. Combining penalties for not meeting those targets may also be used to ensure that the desired levels of reductions in energy consumption, beyond what market forces deliver, are achieved.

EE programs have an impact on how state regulators meet the objective of ensuring just and reasonable rates. To the extent that policy makers provide the state regulators with discretion to decide how large the additional incentives will be and how their costs will be recovered from customers, state regulators will have to grapple with questions like, “At what point do the above-market costs of EE programs cause rates to become unjust and unreasonable, particularly for the customers who don’t benefit from the programs?”

Renewable Portfolio Standards: The Supply Side

As discussed above, renewable portfolio standards are another popular tool for reducing carbon emissions. Many, but not all, state legislatures have RPSs for electric utilities and, where there is retail choice, for competitive suppliers of electricity.51 RPS programs dictate how much retail generation service must be supplied through renewable, clean, or other technologies that are alternatives to traditional baseload generation resources like natural gas–fired generation plants. And, typically, the quotas for renewable resources ramp up over time.

States’ RPS policies vary widely with regard to RPS targets; which types of utilities must meet them (investor-owned utilities, municipal utilities, rural electric cooperatives); the types of resources eligible to meet the requirements; and cost caps. For the most part, the standards are measured by the percentage of retail electric sales. Iowa and Texas, however, require specific amounts of renewable energy capacity rather than percentages, and Kansas requires a percentage of peak demand. While most state percentage targets are between 10 percent and 45 percent, 14 states—California, Colorado, Hawaii, Maine, Maryland, Massachusetts, Nevada, New Mexico, New Jersey, New York, Oregon, Vermont, Virginia, and Washington—as well as Washington, D.C., Puerto Rico, and the Virgin Islands, have requirements of 50 percent or greater. And, as discussed above, some states, including California, Hawaii, and New York, are pursuing 100 percent renewable electric supply portfolios.

The more aggressive RPS programs pose significant challenges for regional electric grid operators, electric utilities, and their regulators. The technical feasibility of providing adequate amounts of electric service reliably around the clock and throughout the year using solely, or even primarily, renewable or clean resources has not been demonstrated yet. And if technical feasibility can be demonstrated, the issue of at what cost remains. California has gone the farthest along this path but also has not yet demonstrated technical or economic feasibility. In fact, recent experience by California during the summer of 2020 raises hard questions about the ability of grid operators and their utilities to furnish adequate and reliable supplies of electric power, while transitioning to a generation fleet that depends primarily (let alone wholly) on renewable resources, without maintaining sufficient amounts of traditional dispatchable peaking or baseload generation assets, including natural gas–fueled power plants.52 Indeed, the challenge of providing adequate and reliable supplies at all times, under all circumstances, is one that even systems with sufficient amounts of traditional dispatchable capacity resources struggle, and at times fail, to meet.53


The path that states must take in order to achieve a generation supply of 100 percent, or even primarily, renewable or clean resources will require eliminating or dramatically reducing natural gas–fired resources from the supply mix. The technical challenge is that, to the extent that this baseload generation technology is eliminated from the mix, the remaining traditional and proven non–fossil fuel baseload technologies, which are nuclear and hydro, won’t be available in sufficient amounts to provide capacity when, or to the extent that, the renewable fleet is unavailable due to its intermittent operation. Adding to this technical challenge are plans for additional retirements from the nuclear fleet. While there has been a great deal of interest in, and some progress made, developing and deploying battery storage technology as a solution to the intermittency of wind and solar, it has not yet been demonstrated to be capable, at scale, of complementing those renewables in a manner that creates, in combination with them, a baseload substitute.

So, at this point, committing to a future without natural gas–fired generation is fraught with risk for three core objectives: adequacy, reliability, and just and reasonable prices. The technical ability to assure adequate supplies of electric service, provided reliably to consumers when they require it and using only or even primarily renewable resources, has not been demonstrated. Nor has the economic feasibility of doing this been proven, which jeopardizes the goal of just and reasonable rates. If policy makers pursue a transition to 100 percent renewable or carbon-free, or even primarily carbon-free, electricity supplies, they should consider hedging their bets by maintaining dispatchable peaking and baseload generation resources, including natural gas–fueled generation plants, as part of the generation fleet, at least until the technical and economic feasibility challenges to such a transition have been solved.


1. Barack Obama, U.S. President, Remarks by the President at the Democratic National Convention (Sept. 6, 2012), in Briefing Room: Speeches and Remarks, White House (Sept. 7, 2012),

2. Exec. Off. of the President, White House, The President’s Climate Action Plan 4, 6 (June 2013),

3. Memorandum from Barack Obama, U.S. President, Power Sector Carbon Pollution Standards (June 25, 2013),

4. Armond Cohen, Obama’s Second Term Climate Priorities, Clean Air Task Force (Jan. 10, 2013),

5. Standards of Performance for Greenhouse Gas Emissions from New, Modified, and Reconstructed Stationary Sources: Electric Utility Generating Units, 80 Fed. Reg. 64,510, 64,513 (Oct. 23, 2015) (to be codified at 40 C.F.R. pt. 60, subpt. TTTT).

6. Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units, 80 Fed. Reg. 64,662, 64,667 (Oct. 23, 2015) (to be codified at 40 C.F.R. pt. 60, subpt. UUUU).

7. Exec. Off. of the President, supra note 2, at 19.

8. Armond Cohen, The President’s Council of Advisors on Science and Technology Has Some Excellent Advice for the President on Climate Change, Clean Air Task Force (May 13, 2013).

9. See Kate Sheppard, Natural Gas Puts Greens in Tough Spot, Mother Jones (Sept. 12, 2012),

10. Press Release, Sierra Club, Sierra Club Ramps Up Beyond Natural Gas Campaign (May 3, 2012),

11. See West Virginia v. EPA, No. 15A773 (U.S. Feb. 9, 2016) (order in pending case).

12. Exec. Order No. 13783, 82 Fed. Reg. 16,093, 16,094–16,095 (Mar. 31, 2017).

13. Repeal of the Clean Power Plan; Emission Guidelines for Greenhouse Gas Emissions from Existing Electric Utility Generating Units, 84 Fed. Reg. 32,520 (July 8, 2019) (to be codified at 40 C.F.R. pt. 60, subpt. UUUUa).

14. Am. Lung Ass’n v. EPA, Nos. 19-1140 et seq., 2021 U.S. App. LEXIS 133 (D.C. Cir. Jan. 19, 2021).

15. Exec. Order No. 13783, 82 Fed. Reg. 16,093 (Mar. 31, 2017).

16. See, e.g., Jeremy Schulman, Every Insane Thing Donald Trump Has Said About Global Warming, Mother Jones (Dec. 12, 2018),

17. See, e.g., Sonia Patel, Trump Administration’s “All-of-the-Above” Strategy Stresses Export Role for Natural Gas, POWER (June 28, 2018),

18. Exec. Order No. 13783, 82 Fed. Reg. 16,093 (Mar. 31, 2017) (emphasis added).

19. Proclamation No. 9659, 82 Fed. Reg. 48,383 (Oct. 12, 2017) (emphasis added).

20. Lindsay Aramayo, More Than 100 Coal-Fired Plants Have Been Replaced or Converted to Natural Gas Since 2011, U.S. Energy Info. Admin. (Aug. 5, 2020),

21. Owen Comstock, Natural Gas–Fired Electricity Generation Expected to Reach Record Level in 2016, U.S. Energy Info. Admin. (July 14, 2016),

22. Mark Morey, U.S. Coal-Fired Electricity Generation in 2019 Falls to 42-Year Low, U.S. Energy Info. Admin. (May 11, 2020),

23. Proclamation No. 9659, 82 Fed. Reg. 48,383 (Oct. 12, 2017).

24. Mickey Francis, U.S. Renewable Energy Consumption Surpasses Coal for the First Time in over 130 Years, U.S. Energy Info. Admin. (Dec. 31, 2020),

25. Id.

26. Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units, 80 Fed. Reg. 64,662, 64,679 (Oct. 23, 2015) (to be codified at 40 C.F.R. pt. 60, subpt. UUUU).

27. U.S. Energy Info. Admin., U.S. Energy-Related Carbon Dioxide Emissions, 2019, at 13 (Sept. 2020), (“Between 2005 and 2019, total U.S. electricity generation increased by almost 2% while related CO2 emissions fell by 33% . . . and non-carbon electricity generation rose by 35%.”).

28. Id. at 4.

29. Id.

30. Id.

31. Galen Barbose, U.S. Renewables Portfolio Standards: 2019 Annual Status Update, at slide 17 (Lawrence Berkeley Nat’l Lab’y July 2019),

32. Renewable Energy Explained: Portfolio Standards, U.S. Energy Info. Admin. (updated Nov. 18, 2019),

33. Iowa State Profile and Energy Estimates, U.S. Energy Info. Admin. (May 21, 2020),

34. Database of State Incentives for Renewables & Efficiency (DSIRE), Renewable & Clean Energy Standards (Sept. 2020),

35. Barbose, supra note 31, slides 10, 12.

36. See, e.g., Cal. Pub. Util. Code § 399.11(a) (2020).

37. Id. § 454.53(a).

38. Colo. Rev. Stat. § 40-2-125.5 (2020).

39. Haw. Rev. Stat. § 269-92(a) (2020).

40. State of La. Exec. Order No. JBE 2020-18, § 2 (Aug. 19, 2020),

41. Me. Stat. tit. 35-A, § 3210.1-A (2020).

42. Nev. Rev. Stat. § 704.7821 (2020).

43. Id. § 704.7820.

44. N.M. Stat. Ann. § 62-16-4 (2020).

45. 2019 N.Y. Laws 106, § 12.d.

46. Va. Code § 56-585.5.B. (2020).

47. Wash. Rev. Code §§ 19.405.010, 19.405.040, 19.405.050 (2020).

48. See Nat’l Conf. of State Legislatures, State Renewable Portfolio Standards and Goals (Jan. 4, 2021),

49. Joe Biden, U.S. President, Remarks by President Biden Before Signing Executive Actions on Tackling Climate Change, Creating Jobs, and Restoring Scientific Integrity (Jan. 27, 2021), in Briefing Room: Speeches and Remarks, White House (Jan. 27, 2021),

50. Joe Biden, Biden for President: The Biden Plan to Build a Modern, Sustainable Infrastructure and an Equitable Clean Energy Future, (last visited Feb. 27, 2021).

51. See Nat’l Conf. of State Legislatures, supra note 48.

52. Following an extreme heat wave in August 2020 and resulting outages, the California Independent System Operator, California Public Utilities Commission, and California Energy Commission produced a preliminary root cause analysis report on October 6, 2020. On January 13, 2021, they issued their final analysis to confirm and supplement their preliminary findings. California ISO, 2021 Summer Readiness (2021) (final report available here),

53. The February 2021 winter storm that gripped the entire midsection of the United States from Canada to Mexico for an extended period with catastrophic health, safety, and economic impacts, particularly in the region served by the Electric Reliability Council of Texas (ERCOT), highlights the scope and scale of that challenge and the costs of failing to meet it. See ERCOT, Review of February 2021 Extreme Cold Weather Event—ERCOT Presentation (Feb. 24, 2021), Depending on resources that are not dispatchable to meet such a challenge would add a compounding dimension of risk to providing and maintaining reliable and adequate service.

The material in all ABA publications is copyrighted and may be reprinted by permission only. Request reprint permission here.

By Eric B. Gallon and Daniel R. Conway

Eric B. Gallon ([email protected]) is a partner in the Columbus, Ohio, office of Porter, Wright, Morris & Arthur LLP. Daniel R. Conway ([email protected]) is a commissioner of the Public Utilities Commission of Ohio. The statements, commentary, and views in this article are those of the authors alone and should not be attributed to any other person or entity.